Nitrogen fertilizer requirements for ethanol production from sweet and ...

Nitrogen Fertilizer Requirements for Ethanol Production from Sweet and Photoperiod Sensitive Sorghums in the Texas Southern High Plains By Parikshya Lama Tamang, B.S. A Thesis In SOIL SCIENCE

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE

Approved Dr. Kevin F. Bronson Chairman of the Committee

Dr. Jeff Johnson Dr. Jennifer Moore-Kucera

Frederick Hartmeister Dean of the Graduate School May, 2010

Copyright 2010, Parikshya Lama Tamang

Texas Tech University, Parikshya Lama Tamang, May 2010

ACKNOWLEDGMENTS This thesis is dedicated to my father Kumba Raj Tamang and my mother Man Shree Lama, who have always inspired and encouraged me to work hard in order to achieve academic excellence. I would like to express my gratitude to my chairman Dr. Kevin F. Bronson for his guidance, encouragement and time throughout my graduate study. I would like to thank Dr. Jeff Johnson and Dr. Jennifer Moore-Kucera for serving on my committee. I would like to thank Adinaryana Reddy Malapati, for technical support in this research. I would also like to thank the faculty and staff members of Texas Tech University and Texas Agrilife Research and Extension Center for their support in my work. And last but not the least, I would like to thank Diwash Neupane for his support.

ii

Texas Tech University, Parikshya Lama Tamang, May 2010

TABLE OF CONTENTS ACKNOWLEDGMENTS ................................................................................................ ii TABLE OF CONTENTS ............................................................................................... iii ABSTRACT ..................................................................................................................v LIST OF TABLES....................................................................................................... vii LIST OF FIGURES ........................................................................................................x CHAPTER I.

INTRODUCTION .......................................................................................................1

1.1 Hypotheses ........................................................................................................6 1.2 Research Objectives ..........................................................................................6 II. LITERATURE REVIEW ............................................................................................7 2.1 Sorghum............................................................................................................7 2.2 Growth Habit in Sorghum .................................................................................8 2.3 Sorghum, an Alternative Raw Material for Biofuel Production ........................ 10 2.4 Water Use in Sorghum .................................................................................... 14 2.5 Nitrogen Use in Sorghum ................................................................................ 15 2.6 Harvesting Stages ............................................................................................ 19 III. MATERIALS AND METHODS ............................................................................... 21 3.1 Statistical Analysis .......................................................................................... 28 IV. RESULTS AND DISCUSSIONS ............................................................................... 29 4.1 In Season Data ................................................................................................ 29 4.1.1 Pre-plant Soil NO3-N Content ............................................................................. 29 4.1.2 In-season Biomass Yield ..................................................................................... 32

iii

Texas Tech University, Parikshya Lama Tamang, May 2010

4.1.3 Normalized Difference Vegetative Index .............................................................. 35 4.1.4 In-season Plant N Concentration ......................................................................... 40 4.1.5 In-season Nitrogen Uptake .................................................................................. 43

4.2 Final Harvest Data ........................................................................................... 46 4.2.1 Dry Stalks Yield................................................................................................... 46 4.2.3 Total Dry Matter Yield ......................................................................................... 50 4.2.3 Final Plant Nitrogen Concentration ...................................................................... 54 4.2.4 Total Nitrogen Uptake ......................................................................................... 57 4.2.5 Bagasse Yield ..................................................................................................... 60 4.2.6 Neutral Detergent Fiber ....................................................................................... 63 4.2.7 Neutral Detergent Fiber Digestibility .................................................................... 66 4.2.8 Sweet Sorghum Juice Yield................................................................................. 69 4.2.9 Brix of Sweet Sorghum Juice .............................................................................. 72 4.2.10 Sweet Sorghum Sugar Yield ............................................................................. 75 4.2.11 Sweet Sorghum Juice Ethanol Yield .................................................................. 78 4.2.12 Cellulosic Ethanol Yield ..................................................................................... 81 4.2.13 Total Ethanol Yield ............................................................................................ 84 4.2.14 Nitrogen Recovery Efficiency............................................................................. 88 4.2.15 Optimum N Fertilizer Rate Estimates For Maximum Production ......................... 90 4.2.16 Optimum N Fertilizer Rate Estimates For Maximum Profit ................................. 92

V. CONCLUSIONS ...................................................................................................... 94 LITERATURE CITED.................................................................................................. 97

iv

Texas Tech University, Parikshya Lama Tamang, May 2010

ABSTRACT Sorghum [Sorghum bicolor (L.) Moench] is a widely cultivated annual cereal crop in the Texas Southern High Plains (SHP) due to its high water use efficiency, rapid growth, and early maturity. Most of the sorghum on the SHP is grain sorghum and the balance is forage sorghums. Interest in sorghums for biofuel feedstock has increased recently as ethanol demand in the USA expands. Nitrogen (N) is the nutrient that plays the most crucial role in overall growth and yield of the crop. It is the most important input to sorghum production in terms of dollars and energy costs. The amount of N required by sorghum depends upon its yield potential in diverse growing conditions, soil organic N breakdown, and the amount of residual NO3-N in the soil before planting. There is no information available on N fertilizer requirements for economically optimum ethanol yield from sweet or forage sorghum production in the SHP. The objective of this study is to compare the ethanol yields and determine optimal nitrogen fertilizer needs for ethanol production from sweet sorghum and photoperiod sensitive (PPS) sorghum with limited irrigation in the SHP. The study was conducted on an Acuff sandy clay loam at Texas Agrilife Research and Extension center farm near Lubbock, Texas in 2008 and 2009. Five different N fertilizer rates; 0, 67 101, 134 and 168 N kg ha-1 and four cultivars of sorghum; Della, M81E (sweet sorghums), Sugar graze ultra and Maxigain (PPS sorghums) were used. Total dry matter (TDM) yields in 2008 were less than in 2009. The mean TDM yield for 2008 was 11,971 kg ha-1, and in 2009 the average TDM was v

Texas Tech University, Parikshya Lama Tamang, May 2010 14,018 kg ha-1. Nitrogen fertilizer response and cultivar response in TDM were observed only in 2009. Bagasse yields responded positively to N fertilizer in 2008 and 2009. Greater TDM was recorded from PPS sorghum than sweet sorghum cultivars. Sugar yields averaged 1560 and 2200 kg ha-1 for 2008 and 2009, respectively, with no effect of cultivar, N or cultivar x N. Cellulosic ethanol yields were greater with PSS sorghums than with sweet sorghums in both years. However, total ethanol yields were greater with sweet sorghums than PPS sorghums in both years. Ethanol yield from sweet sorghum juice was greater in 2009 than in 2008. In 2008, N application did not increase ethanol yield from juice but in 2009, the cultivar M81E showed positive N response. In 2008, cellulosic ethanol yield was not affected by N rate, but in 2009, cellulosic ethanol yield increased with N rate. Total ethanol yield was greater in 2009 than in 2008, with an average of 2143 kg ha-1. In 2008 no N response or N x cultivar interaction were observed in total ethanol yield. Total ethanol yields responded quadratically to N fertilizer rate in 2009. Among cultivars, the highest total ethanol yield in 2009 was produced with M81E. The optimum agronomic N fertilizer rate for ethanol and TDM across all four sorghums was 108 kg ha-1 respectively in 2009. The optimum N fertilizer rate for maximum profit with $ 0.70 kg N -1 and $0.50 L-1 ethanol was 101 kg ha-1.

vi

Texas Tech University, Parikshya Lama Tamang, May 2010

LIST OF TABLES 1. Physical and chemical characteristics of Acuff sandy clay loam, Spring 2008, Lubbock, TX. .................................................................................................... 26 2. Growing season rainfall and irrigation data in 2008-2009. Lubbock, Texas. ......... 27 3. Dry biomass yield of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. ................................................................................... 33 4. Dry biomass yield of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. ................................................................................... 34 5. Crop Circle normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. ........................... 36 6. GreenSeeker normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. ........................... 37 7. Crop Circle normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. ............................. 38 8. GreenSeeker normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. ............................. 39 9. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. .......................................................................... 41 10. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. ............................................................................ 42 11. Nitrogen uptake of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. ................................................................................... 44 12. Nitrogen uptake of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. ................................................................................... 45 13. Dry stalks yield of sorghums as affected by cultivar and N fertilizer rate, at final harvest, September 2008, Lubbock, TX. ............................................................ 48 14. Dry stalks yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. ............................................................ 49

vii

Texas Tech University, Parikshya Lama Tamang, May 2010 15. Total dry matter yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. .................................................... 52 16. Total dry matter yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. .................................................... 53 17. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. .................................................... 55 18. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. .................................................... 56 19. Total N uptake of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. ............................................................ 58 20. Total N uptake of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. ............................................................ 59 21. Bagasse yield of sweet sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. .................................................... 61 22. Bagasse yield of sweet sorghums as affected by cultivar and N fertilizer rate, September 2009, Lubbock, TX. ......................................................................... 62 23. Neutral detergent fiber of sorghum stalks as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX.................................................................................... 64 24. Neutral detergent fiber of sorghum stalks as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX.................................................................................... 65 25. Neutral detergent fiber digestibility of sorghums as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. .................................................................... 67 26. Neutral detergent fiber digestibility of sorghums as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. .................................................................... 68 27. Juice yield of sweet sorghums as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. .................................................................................................... 70 28. Juice yield of sweet sorghums as affected by cultivar and N fertilizer rate, September 2009, Lubbock, TX. ......................................................................... 71 29. Brix of sweet sorghum juice as affected by cultivar and N fertilizer rate, 2008 Lubbock, TX. .................................................................................................... 73 viii

Texas Tech University, Parikshya Lama Tamang, May 2010

30. Brix of sweet sorghum juice as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. ............................................................ 74 31. Sugar yield of sweet sorghum juice as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. .......................................................................................... 76 32. Sugar yield of sweet sorghum juice as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. .......................................................................................... 77 33. Juice ethanol yield of sweet sorghums as affected by cultivar and N fertilizer rate, September 2008, Lubbock, TX. ......................................................................... 79 34. Juice ethanol yield of sorghums as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. .................................................................................................... 80 35. Cellulosic ethanol yield of sorghums as affected by cultivar and N fertilizer rate, 2008 Lubbock, TX. ........................................................................................... 82 36. Cellulosic ethanol yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. .................................................... 83 37. Total ethanol yield of sorghums as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. .................................................................................................... 86 38. Total ethanol yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. ............................................................ 87 39. Nitrogen recovery efficiency of sorghum as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX.................................................................................... 89 40. Proc mixed procedure for the regression of total ethanol yield from sweet and PPS sorghums (average across cultivars) on nitrogen fertilizer rate, Lubbock, 2009. . 91 41. Economic optimum N fertilizer rate (EONR) ethanol production from sweet and photoperiod sensitive sorghums, Lubbock, 2009................................................ 93

ix

Texas Tech University, Parikshya Lama Tamang, May 2010

LIST OF FIGURES 1. U.S.A. corn production and use for fuel ethanol ……………………………3 2. Spring pre-plant soil NO3-N content by depth, Lubbock, TX, 2008……………………………………………………...30 3. Spring pre-plant soil NO3-N content by depth as affected by N fertilizer rate, Lubbock, TX, 2009...…………………………………………………….31

x

Texas Tech University, Parikshya Lama Tamang, May 2010

CHAPTER I INTRODUCTION

Increasing costs of fossil fuels along with growing concern over their depletion within the next few decades has created a strong interest in biofuels. Crops have potential to produce renewable sources of liquid transportation fuel, which is an invaluable way to reduce oil imports. It is envisioned that transportation fuel from biomass will increase significantly by 0.5% of US transportation fuel consumption in 2001 to 4% of transportation fuel consumption in 2010, 10% in 2020 and 20% in 2030 (Perlack et al., 2005). About 20,680,000 barrels of oil were consumed each day in the United States in 2007 (http://www.nationmaster.com/graph/ene_oil_con-energyoilconsumption&date=2007). The International Energy Outlook (2005) projected that there would be an increase in worldwide energy consumption by 57% from 2002 to 2025 levels. This will require the development and expansion of alternative sources of energy (http://www.sollaring.org/ec/ec/html). The consumption of fossil fuels contribute an increasing portion of the CO2 flux to the atmosphere, raising concerns about global warming. New forms of energy are required which are inexpensive, readily available, obtainable from renewable sources and emit less carbon. In 2005, biofuel production was 31 million tons worldwide which is expected to more than double in 2015 (www.ifp.com/.../3/.../IFP-Panorama07_05Biocarburants_monde_VA.pdf). It is forecasted that the world‘s ethanol production will be more than 75 billion Li in 2012 and ethanol production is expected to increase 1

Texas Tech University, Parikshya Lama Tamang, May 2010 by 5% from 2008 to 2012 (Market Research analyst, http://www.marketresearchanalyst.com/2008/01/26/world-ethanol-productionforecast-2008-2012/). The USA can approximately produce 1.3 billion dry tons of biomass each year that can be used for ethanol production (Perlack et al., 2005). Corn (Zea mays L.) grain use for ethanol feedstock has increased dramatically over the last few years in USA (Fig. 1). However, even if all the US corn is dedicated to produce ethanol, it would fail to meet the country‘s total transportation fuel demand. Moreover, the use of corn is limited, since it is also used as food and feed source, and water-use and N requirements are very high for corn. The development of crops grown mainly for biofuel production will be required to generate a large and sustainable supply of biomass for the production of biofuel. Sorghum [Sorghum bicolor (L.) Moench] is one among many species used as bioenergy crops, which are highly productive, drought tolerant and can produce lignocellulose, sugar and starch (Rooney et al., 2007). Sweet sorghum with its high sugar content, wide adaptability, lower water requirement is being considered as a potential alternative source of biomass energy (Keeney et al., 1992). Sorghums have many important advantages over other biofuel crops in the SHP.

2

Texas Tech University, Parikshya Lama Tamang, May 2010

Million Bushels Corn

U.S. Corn Production and Use for Fuel Ethanol

Figure 1. U.S.A. corn production and use for fuel ethanol. (US. Department of Energy, 2010).

3

Texas Tech University, Parikshya Lama Tamang, May 2010 In general, sorghums are more water-use efficient than corn and typically require less water to produce a certain level of dry matter (Martin et al., 1990). Sorghum requires 40 – 50% less water than corn and four times less water than sugarcane. Even when water use efficiencies of corn and sorghum are similar, the water requirements of corn are greater because of earlier planting dates and longer growing seasons (Howell et al., 1997). The Ogallala aquifer in the Texas High Plains is being depleted, and any ―renewable energy‖ sources such as biofuel should not deplete groundwater. Sorghums are able to maintain high yields under water stress, and resume growth after prolonged periods of drought (Sanderson et al., 1992). Additionally, sorghums offer several pathways to produce ethanol. Three common pathways include: i) starch to ethanol from grain sorghum, ii) sugar to ethanol from stalks of sweet sorghum, and iii) cellulosic ethanol from bagasse (stalks after sugar extraction). Photoperiod sensitive forage sorghums are characterized by tall growth and large dry matter yields. Sarath et al. (2008) states that forage sorghum can grow in conditions where corn cannot grow, has the ability to produce high biomass, and is already established as an industrial crop. Photoperiod sensitive sorghum can grow up to 1.8 4.5 m tall. It requires a day length of less than about 12 hours to initiate flowering. Consequently, plants will remain in the vegetative stage for longer periods during the growing season, and could produce high ethanol output from cellulosic conversion. Nitrogen is the element required in the greatest amount in crops, including sorghums. Nitrogen-based fertilizers are synthesized using the Haber-Bosch process, 4

Texas Tech University, Parikshya Lama Tamang, May 2010 which produces ammonia by reacting natural gas-derived hydrogen and N. This process requires high energy and thus represents significant energy input for crop production. Recent studies indicate that energy inputs are dominated by N fertilizer inputs rather than tillage and other field operations (Wienhold et al., 2006; Rathke and Diepenbrock, 2006; Rathke et al., 2007). Rathke and Diepenbrock, (2006) found that 48% of all the energy inputs used to cultivate rapeseed (Brassica napus), and 25% of the total energy inputs of finished biofuel could be attributed to fertilizer N. The energy used to produce N fertilizer inputs represented nearly 10% of the energy output of rainfed corn (Wienhold et al., 2006). This relatively large influence of N fertilizer inputs on the overall energy balance should be an important consideration in biofuel crop production system. Moreover, available soil N to the crop will also influence water use efficiency of grain and forage yield. Nitrogen fertilizer requirements for sorghum biofuel production, especially under deficit or limited irrigation needs to be evaluated. Although information exists on fertilizer requirements for grain sorghum (Booker et al., 2007), information on N fertilizer requirements for economic optimum ethanol yield from production of sorghums in the High Plains is lacking. Data on optimum N fertilizer rates for sweet sorghum yields, sugar yields, and ethanol yields are mostly from the southeastern states such as Louisiana (Ricaud and Arceneauz, 1988) and Georgia (Gascho et al., 1984).

5

Texas Tech University, Parikshya Lama Tamang, May 2010 1.1 Hypotheses 1.

Ethanol yields from sweet sorghum cultivars are greater than with PPS sorghum cultivars.

2. There is an optimum N fertilizer rate for ethanol production from sweet and PPS sorghum beyond which ethanol yield decreases.

1.2 Research Objectives 1. To compare ethanol yields from sweet sorghums and PPS sorghums with limited irrigation in the Texas SHP.

2. Determine N requirements for ethanol production from sweet sorghums and PPS sorghums with limited irrigation in the Texas SHP.

6

Texas Tech University, Parikshya Lama Tamang, May 2010

CHAPTER II LITERATURE REVIEW 2.1 Sorghum Sorghum belongs to the family Graminaceae, genus Sorghum species bicolor (L,) [Moench] (Martin et al., 1990). Worldwide, sorghum [Sorghum bicolor (L.) Moench] is produced on more than 49 million hectare in a year and ranks fifth among the grain crops production (Monk et al., 1984). Sorghum is grown in the United States of America in the Central and Southern Plains including Texas, Kansas, Nebraska, Oklahoma, and Missouri. Initially, sorghum was grown as a source of sugar for syrup, later with the settlement of the semiarid West, drought resistant forage sorghum came into demand. By the 1950s, 90% of the area of sweet sorghum in the United States was used for forage (Undersander et al., 1990). The United States ranks second in total production with 17 % of the world production and the USA is first in exporting sorghum. The USA accounts for 89 % of world sorghum exports in the year 2005 and 2006, out of which 69% is exported to Mexico alone. In United States approximately 2.5 million hectares of sorghum are harvested each year according to the data of 2005 and 2006. (US Grains Council). In 2007, about 7.7 million acres of grain sorghum were produced and more than 6 million acres of forage sorghum were grown in the USA with total production of 58 million tons of biomass (USDA, 2008, Data and Statistics). In 2008, 3 million acres of grain sorghum harvested in Texas statewide with 1.5 million acres of grain sorghum was harvested in West Texas alone. For silage, 130,000 acres of sorghum were harvested statewide in 2008. (USDA. National Agricultural Statistical Service 2008). 7

Texas Tech University, Parikshya Lama Tamang, May 2010 Forage sorghum was harvested on 2.4 million ha in the USA in 2007 with a total production of 58 million tons of biomass (USDA, Data and Statistics 2008). 2.2 Growth Habit in Sorghum Sorghum can be divided into sweet sorghum, grain sorghum and forage sorghum (Almodares et al., 2008b and Monk et al., 1984). Among sorghums, sweet sorghum has high accumulation of sugar in its stalk (Monk et al., 1984). Sweet sorghum is well adapted to temperate and sub-tropical region. Forage sorghum is best grown in warm, fertile soils, (Undersander et al., 1990), and in a wide variety of soils with pH levels from 5.5 to 8.5, and varying moisture levels (Miller and Stroup, 2004). Cool, wet conditions, limit sorghum growth. The growth habit and the general appearance of sorghum are similar to that of corn, which uses the C4 photosynthetic pathway but with similar or higher biomass production than corn. Sorghum can produce stalks yields as high as 54-69 t ha-1 (Almodares et al., 2008b). Sorghum has a well developed root system that can extend to a maximum depth of 1.5 m (Weaver, 1926). Forage sorghum whose stem are solid and erect, grow between 1.8 and 3.6 m and produce more dry matter than grain sorghum (Undersander et al., 1990). The plant requires up to 70-100 mm of moisture every 10 days in early growth stages. It develops slowly and as it grows taller, the root system penetrates more deeply into the soil absorbing water from deep in the soil. Thus, sorghum tolerates prolonged periods of drought (Doggett, 1988) and grows well in high light and temperature intensity (Monk et al., 1984). It becomes dormant in the absence of adequate water, but rarely wilts. Forage sorghums produce the same 8

Texas Tech University, Parikshya Lama Tamang, May 2010 amount of dry matter as corn using approximately 40 – 50% less water (Miller and Stroup, 2004). Grain yields with sweet sorghum are usually low, i.e. about 1500 kg ha-1 compared to grain sorghum (Wu et al., 2009). Juice extracted from the stalks is the most important product in sweet sorghum. The juice is high in sugars, which can be rapidly, but indirectly with a refractometer. Brix (i.e. degrees Brix) is a measure of the fraction of sugar per hundred parts solution, by mass. Brix measures total soluble solids or carbohydrate content in the juice which in sorghum is comprised mostly of sucrose. Brix can range from 14.32% 22.85 % in different varieties of sweet sorghum (Almodares and Sepahi, 1996). Reddy et al. (2005) reported that sweet sorghum has wider adaptability because of high sugar accumulation, rapid growth and biomass production potential (Almodares et al., 1994a), and is therefore well-adapted to sub-tropical and temperate regions of the world. Photoperiod sensitive sorghum does not flower under normal production systems, i.e. until the day length is less than 12 hours and 20 minutes (McCollum et al., 2005). It is capable of producing high lignocellulosic dry matter yields with no production of grains at most latitudes in the United States (Propheter et al., 2010). Photoperiod sensitive sorghum has higher water use efficiency than corn and produces equal to or greater biomass than corn even after using 33% less water. In comparison to corn, PPS sorghum has a tendency to produce more biomass than brown mid rib (bmr) and non-bmr sorghum (McCollum et al., 2005).

9

Texas Tech University, Parikshya Lama Tamang, May 2010 2.3 Sorghum, an Alternative Raw Material for Biofuel Production The high cost of gasoline, together with finite oil and gas reserves has created a need to produce an alternative energy sources, i.e. biofuels. Thus, sorghum has been proposed as a biomass crop for the fermentation into ethanol fuel (Macesic et al., 2008). Sweet sorghum, in particular, is gaining greater interest as an alternative bioenergy crop as it has high concentration of soluble sugars in the plant sap or juice which can easily be turned into a potent biofuel, using methodology similar to what the sugarcane industry uses. The sweet sorghum juices extracted from the stalks are rich in sugars, with the total solids being about 80 % sugars. In general sucrose makes up to 55% of the dry matter, glucose 3.2% and cellulose and hemicelluloses of 12.4% and 10.2% respectively (Billa et al., 1997). Sweet sorghum‘s ability to tolerate drought conditions and grow well on marginal lands make it attractive as a biofuel crop. Sweet sorghum has superior water use efficiency and the ability to withstand severe water stress condition of sweet sorghum than several other C4 plants, especially corn and grain sorghum (Steduto and Unlu, 2000; Steduto et al., 1997). Keeney and Deluca, (1992) reported that due to the increased environmental cost of fossil fuel along with the growing concern over their depletion within the next few decades, biofuel energy will be used as an alternative source of energy. Therefore, sweet sorghum [sorghum bicolor (L) Moench] with its higher sugar content, wider adaptability, lower water requirement is considered as an attractive, potential alternative source of energy. 10

Texas Tech University, Parikshya Lama Tamang, May 2010 Ethanol is produced from the fermentation of simple sugars that are squeezed directly from stalks. There are several other factors that affect the sorghum‘s ethanol fermentation efficiency. Wang et al. (2008) summarized these factors including; protein digestibility, level of extractable protein, protein and starch interaction, mash viscosity, amount of phenolic compounds, ratio of amylase to amylopectin and the formation of amylase-lipid complexes in the mash. Sweet sorghum, a C4 plant is an efficient plant in terms of photosynthesis and directly produces fermentable sugar as well as grain. It is an ideal crop for the simultaneous production of energy and as well as food. Moreover, it produces higher yield even after an abbreviated production cycle and requires minimal amount of fertilizers and irrigation. Sweet sorghum has more potential than other sugar crops due to its low input cost and high production characteristics. Reddy and Sanjana, (2003) reported that sweet sorghum with its characteristics of rapid growth along with higher production potential and high sugar content can be widely adopted. In one study about the comparative advantage of sweet sorghum versus sugarcane and sugarcane molasses in terms of ethanol production, it was found that the cost of cultivation for sweet sorghum was much lower than sugarcane production. Given the cost of production, revenue from sorghum by producing ethanol was higher than from sugarcane and sugarcane molasses. Ethanol made from the juice of sorghum stalks has four times the energy yield of corn based ethanol. Putnam et al. (1991) found that in a normal year, sweet sorghum ethanol yield is similar to that of corn yield but in a dry year sweet sorghum 11

Texas Tech University, Parikshya Lama Tamang, May 2010 cultivars can produce higher ethanol yield than corn. Sweet sorghum produces about eight units of energy for every unit of energy used in production, similar to sugarcane. The quality of sugar or jaggery prepared from sweet sorghum is comparable to that of sugarcane (Singh and Singh, 1986). In spite of the comparable energy and quality of sugar produced from sweet sorghum juice with sugar cane, Reddy et al. (2005) reported that sweet sorghum is superior to sugarcane and sugar beet, the two main sources of sugar production in the world. They cited the unique characteristics, i.e. drought tolerance, water logging tolerance, saline-alkaline tolerance, rapid growth high sugar accumulation, high biomass production potential and wide adaptability. The major drawbacks of sugarcane and sugar beet for ethanol production are the high water requirements, and water and air pollution which occurs from molasses-based ethanol production. In addition to the sugar production in juice, the bagasse, or stalks left over from juice extraction, are a valuable resource. Bagasse can be used for animal feed, returned to the soil to maintain soil quality or converted to ethanol via cellulosic conversion. Bagasse is rich in cellulose and hemicelluloses. Dahlberg (2007) reported that sorghum is unique as it fits into many of the biofuel production schemes by providing starch from grain, sugar from juice pressed from sweet sorghum stalks, and high biomass production from sorghum such as forage sorghum. However, as shown by Chen et al, (2007), ethanol can also be successfully produced from sorghum hays through a series of chemical treatments, enzymatic hydrolysis and fermentation processes. The sorghum hays contained approximately 28.62% – 38.58% glucan, 12

Texas Tech University, Parikshya Lama Tamang, May 2010 11.9% - 20.78% xylan and 22.01% – 27.57% lignin making it good candidate for ethanol production via cellulosic conversion. Photoperiod sensitive sorghum is tall and have large dry matter yields with higher potential of ethanol production from sugar and cellulosic conversion. According to McBee et al. (1986), the most common compounds produced in sorghums are structural carbohydrates, i.e. lignin, cellulose and hemicelluloses ranging from 45-53%, 38-49% and 43-46% in grain sorghum, sweet sorghum and high energy sorghum respectively. These nonstructural carbohydrate and structural components are mostly found in large quantities in sorghum stems than in leaf blades. For example stems contained 716 to 516 g kg-1 and blades contained 652 to 567 g kg-1 of structural components and 12 to 39 g kg-1 of more lignin in stems than in blades (McBee et al., 1990). Cellulosic ethanol has a higher net energy ratio and emits less CO 2 than first generation ethanol biofuel crops. The ethanol from lignocelluloses emits 0.23 kg l -1 of CO2 while ethanol from corn, sugarcane and canola emits 1.94, 1.08 and 0.91 kg l-1 of CO2 respectively (Lemus et al., 2009). Sorghum can be grown in semi arid region as it requires 40 % less water than corn. Sorghum thus, can be a useful option for acquiring sustainable economic development at the present situation where we face unpredictable climatic variation and continuing decline of water resources (Wang, 2008). Therefore, sorghum can be an important feed stock for ethanol production and can contribute significantly to the ethanol supply of the nation. 13

Texas Tech University, Parikshya Lama Tamang, May 2010 2.4 Water Use in Sorghum Water is essential to maintain all the vital activities of plants. Scarcity of water under rain fed agriculture often retards the growth of the crop, but sorghum can thrive even in prolonged drought conditions. Therefore, it can be a useful crop in areas with limited water availability. Curt et al. (1995) demonstrated that water use efficiency in sorghum under three different treatments of low, medium and high water supply was similar without any significant variation. Moreover, it was found that the sugar content of sweet sorghum juice at these different irrigation treatments was not affected. Although sorghum is well-known as a productive crop under water limiting conditions, it responds well to irrigation with increased N uptake and biomass. Montemurro et al. (2002) observed that N uptake was much higher in well-irrigated condition than in stressed conditions. In stressed conditions, mineral N accumulated in the soil but not in the well-irrigated treatments. Nitrate leaching is possible at the end of the cropping cycle if nitrogen application is done without taking into consideration soil water content. Sorghum has a similar climatic and seasonal requirement to corn, but it can withstand drought conditions for longer durations. This is due to the fact that sorghum has more secondary roots and a smaller leaf area per plant. Moreover, the leaves and stalks of sorghum wilt and dry more slowly than that of corn, which enables sorghum to grow well even in prolonged drought. Farre et al. (2006) found that in comparison to corn, sweet sorghum had profuse vegetative growth, higher bio-mass and higher yield and higher harvest index under moderate or severe water deficit treatments. It was concluded that the characteristic of sweet sorghum such as the greater ability to 14

Texas Tech University, Parikshya Lama Tamang, May 2010 penetrate and extract water from deep soil layers, short duration and better leaf characteristics (low K, erect leaves) made sorghum alternatively viable to corn in water stressed conditions. 2.5 Nitrogen Use in Sorghum Mineral elements are required by almost all living organisms to sustain life and to grow and develop. Of all the mineral elements required for plant growth, N is the most essential elements and is required in the greatest quantities (Ashiono et al. (2005). With the application of N fertilizer, the soluble carbohydrate content (sucrose) in sweet sorghum (Galani et al., 1991, Pholsen et al., 2004) and biomass (Pandey et al., 2001) was increased. Similarly, Leible and Kahnt, (1991) reported that the application of N increased stalk yield and sucrose content in sweet sorghum up to a aximum yield of 22.7 t ha-1 of dry matter and 6.5 t ha-1 of free fermentable sugar. Pandey et al. (2001) reported that sorghum had greater responses to N than corn which was calculated as incremental increases in yield per applied. It was found that for each kg of N applied, biomass yield increased by 55.5 kg per hectare in sorghum. In addition to N fertilizer, relative humidity and amount of rainfall are also very important for high forage, dry matter and seed yield in sweet sorghum production. On the other hand, Almodares et al. (2007) reported that stalk yield, sucrose content and sugar concentration (degree Brix) (Reddy et al., 2008) of sweet sorghum were not influenced by the application of different levels of N fertilizer. With increasing level of N fertilizer application, crude protein and crude fiber content of 15

Texas Tech University, Parikshya Lama Tamang, May 2010 forage sorghum (Mahmud et al., 2003) and biomass and crude protein of sweet sorghum cultivar Keller increased significantly but soluble carbohydrate content decreased significantly (Almodares et al., 2009), Biomass, crude fiber and protein content, plant height, stem diameter, fodder yield of forage sorghum (Mahmud et al., 2003) and green and dry matter yield of sorghum (Sorghum bicolor L.) cultivar JS-263 was increased with increasing level of N fertilizer. Neutral detergent fiber (NDF) was decreased by the application of N fertilizer (Ayub et al., 2002). Pholsen et al, (2004) also reported that brix value, crude protein and total dry weight of forage sorghum were increased with rate of N fertilizer, but the N application had no effect on NDF. The dry matter yield of sorghum increased from 10.14 to 11.7- t ha-1 and crude protein yield of sorghum increased from 0.52 to 0.84 t ha-1 with N fertilizers rate, i.e. 40 to 100 N kg ha-1 (Raj et al., 1988). Due to the dynamic nature of N, over-application of N fertilizer can result in losses through process such as leaching, runoff, denitrification, erosion; therefore, N deficiencies are common. Sorghum plants deficient in N are usually stunted, spindly and pale in color and with reduced yield. The vegetative stage is also shortened, causing early maturity. Nitrogen deficiencies often result in reduced dry matter, crude protein and grain yields. Nitrogen deficiency resulted into lower biomass production in sorghum cultivar DK 44C due to reduced leaf area, reduced chlorophyll content and photosynthetic rate (Zhao et al., 2005). Although N plays a very important role for good growth and development of sorghum, over-fertilization is often harmful as it results in lower yield and quality. 16

Texas Tech University, Parikshya Lama Tamang, May 2010 Separate studies by Meli, (1991) and Teli, (1993) concluded that length and weight of stalks was increased by the application of N but also reported that high doses of N reduced the quality of juice. Optimum amounts of N fertilizer combined with other input factors play crucial roles in yield and overall quality of sorghum products. The optimum amount of fertilizer is related to maximum efficiency of production. Upon the addition of nutrients, yield increases but up to the certain limit, then it starts to decrease even after the further addition of nutrients. Wiedenfeld et al. (1984) reported that biomass yield and N uptake by sweet sorghum were enhanced with the application of 112 kg N ha-1, but with the increased application of 224 kg N ha-1 neither the biomass yield nor total N uptake was increased. Ethanol yield increased with N uptake. Ethanol yield and N utilization by sweet sorghum compared favorably to grain crops when it is used as feedstock to produce ethanol. Almodares et al. (2009) reported that excessive applications of N fertilizer could decrease soluble carbohydrates in corn and sorghum. They reported that 200 kg N ha-1 optimized biomass and protein content. Patel, (1998) reported that green fodder and dry matter yield of forage sorghum increased as N fertilizer rate increased from 0 to 75 kg N ha-1. An N rate of 150 kg ha-1 maximized plant, stem diameter and maximum crude protein % in sorghum (Sorghum bicolor L.) cultivar JS-263 (Ayub et al., 2002). Pandey et al. (2001) reported that a significantly higher biomass yield from sorghum variety ‗Sepon-82‘ was obtained with the application of 180 kg N ha-1. Reddy et al. (2008) concluded that an optimum dosage of 64 N kg ha -1 (half as basal 17

Texas Tech University, Parikshya Lama Tamang, May 2010 and half as topdress) can be applied to obtain maximum sugar yields in sweet sorghum. Bernal et al. (2001) reported similar results, that at low levels of N supply, the sorghum varieties ICI 770 produced high yield which did not increase even with increased rates of N supply. Similarly, another sorghum variety, Sorghica Real-40 had low yield at low level of N and its yield also did not increase even with the addition of high levels of N. Sumantri and Lestari (1997) observed an increase in sorghum stalk yield only up to 90 kg N ha-1, even when maximum rate of 120 kg N ha-1 was applied. Turgut et al. (2005) reported that both forage and the dry matter yield increased up to 150 kg N ha-1, while yield decreased with 200 kg N ha -1. Thus, 150 kg N ha-1 was reported to be the optimum rate to obtain higher forage sorghum yield under irrigated condition. Similarly, Patel et al. (1994) reported that forage production increased with increasing N application, but the response was significant only up to 40 kg N ha-1. Crude protein content and yield decreased with higher N applications. Higher dry matter yield of 12 t ha-1 were obtained from forage sorghum with the application of 120 kg N ha-1, and t 0 and 60 kg N ha-1 resulted in 5.8 and 9.8 t ha-1, respectively (Patel et al., 1992). The typical N fertilizer application often results in the loss of N through various pathways. Raun and Johnson, (1999) reported that N use efficiency for sorghum [Sorghum bicolor (L.) Moench] is usually 33 % and the remaining 67 % represents loss of N fertilizer. Nitrogen losses can be from plant emission, soil denitrification, surface runoff, volatilization and leaching. Increasing N use efficiency 18

Texas Tech University, Parikshya Lama Tamang, May 2010 can decrease NO3 accumulation and its leaching. Nitrogen use efficiency usually depends on crop health and the magnitude of N losses through different process. Nitrogen loss potential is influenced by the fertilizer source of N and its management as well as weather conditions and soil types. Therefore, N fertilizer must be managed carefully to minimize N losses specific to the N source. Different methods of fertilizer application are innportant factors which influence N use efficiency and N losses. However, N use efficiency can be improved by the combined application of fertilizer with organic residues. Changade et al. (2006) found that the application of 75 % recommended dose of fertilizer (60:30:30 kg NPK ha-1) along with farm yard manure was found to be optimum for producing good juice quality in sorghum genotype ‗SSV-84‘. They reported a juice yield of 11969 l ha-1, brix % of 17.37 % and sucrose content 9.23 %. Brix in juice decreased in response to increasing N, P and K levels. Zougmore et al. (2003) similaryly reported that optimum combination of organic resources and fertilizer improved the total yield and N use efficiency in sorghum. 2.6 Harvesting Stages Timing of harvest of has a great impact on the quantity and quality of sweet sorghum juice. The best time to harvest sorghum is at physiological maturity where the plant has maximum total dry weight, greater accumulation of sugar and brix value. Moreover, the uptake of nutrients cease at this stage. Similar results were obtained by Jadhav et al. (1994) who found brix to be positively and significantly correlated with

19

Texas Tech University, Parikshya Lama Tamang, May 2010 sucrose at maturity. At physiological maturity, sorghum juice contained more brix, purity, sucrose and less reducing sugar ash etc than at milking stage. Sweet sorghum varieties with high level of brix, purity, sucrose content, commercial cane sugar percentage and low level of starch poly-phenols, ash and reducing sugars are ideal for good sugar production. Channappagoudar et al. (2007) also found similar results that total sugar, non-reducing sugar and brix value of juice increased between flowering and physiological maturity. With the application of 10:75:37.5 N, P2O5, K2O to the several sorghum genotypes, higher juice extractability percent at physiological maturity and higher brix value were reported. The result obtained by Almodares et al. (2007) showed that the best stage to harvest sweet sorghum in order to obtain the highest brix value was at physiological maturity and before chilling stage. In the flowering stage brix had not yet reached a maximum. At the physiological maturity stage, cultivar Rio had higher sucrose content than any sweet sorghum cultivars.

20

Texas Tech University, Parikshya Lama Tamang, May 2010

CHAPTER III MATERIALS AND METHODS The study was conducted at Texas Agrilife research and extension center farm near Lubbock, Texas. Location of the site is 33o6‘N, 101o 48‘ W at an elevation of 1000 m above sea level. The soil at this site is an Acuff sandy clay loam (fine-loamy, mixed, superactive, thermic, Aridic Paleustoll). The physical and chemical properties of the soil are shown in Table 1. The plots at this site are oriented in a north-south direction, and row spacing was 1 m. The experimental design was randomized complete block design, two- way factorial with three replications or blocks. Main plots, 16, 1-m rows wide and 200 m long were assigned to cultivar. Each mainplot was divided into 5, 4-row x 150 m subplots which were randomly assigned to five N-fertilized treatments (0, 67, 101, 134, and 168 kg N ha-1). Soil samples from 0 - 0.15 m deep were collected by sampling with a hand probe on the 25th of February 2008 and on 11th of March 2009. Ten samples per plot were taken and mixed together. Soil samples of 0.15 - 0.3, 0.3 - 0.6 and 0.6 - 0.9 m depths were collected with a Giddings machine (Giddings Inc. Fort Collins, CO) on 28th February 2008 and 18th March 2009. Two samples were taken per subplot and the soil samples from the same depths were mixed together. Soil samples were dried, ground and crushed to a pass a 4 mm sieve. The soil samples were extracted with 1 M KCl and analyzed for NO3-N with a colorimeter (Adamsen et al., 1985).

21

Texas Tech University, Parikshya Lama Tamang, May 2010 In 2008 and 2009, four different cultivars of sorghum, i.e. Della, Maxigain, M81E and Sugar graze ultra were planted on 21st of May. ‗Della‘ and ‗M81E‘ are sweet sorghum cultivars, and ‗Maxigain‘ and ‗Sugar graze ultra‘ are PPS sorghums cultivars. The seeding rate was 4.1 lb acre-1 and the row spacing was 1 m. Plant emergence was observed 27th of May. In 2009, the same cultivars were planted on 29th of May. In 2008, sorghum was furrow irrigated three times in a growing season, first on 16th of June, second on 12th of July and the last on 30th of July. In 2009, preplant row irrigation was applied on 23rd of May, and furrow irrigation was done on 23rd of June, 17th of July and on 10th of August. Rainfall and irrigation data for 2008 and 2009 is shown in Table 2. Nitrogen fertilizer treatments were applied as urea ammonium nitrate (32-0-0) side-dressing at V4 on 27th of June 2008 and on 22nd of June 2009. Fertilizer was knifed-in, 10 cm deep and 10 cm off the seed row. Plant samples for biomass and N uptake in both sweet sorghum and PPS sorghum cultivars were harvested at the V8 to V10 stage. Plant samples within a distance of 2 feet were taken from the middle two rows of each plot on 21 st of July 2008 (V10) and on 10th of July 2009 (V8). Plant samples were dried at a temperature of 65 oC then weighted for dry matter. Dried plant samples were ground to about 1 mm size which was later analyzed for N using a N analyzer (LECO Corporation, St. Joseph, MN). Canopy reflectance measurements were taken at V8-V10 with a Crop CircleTM ACS-210 (Holland Scientific Inc., Lincoln, NE) and a GreenSeeker TM spectroradiometer (NTech Industries, Ukiah, CA) at 1 m above the canopy. The Crop 22

Texas Tech University, Parikshya Lama Tamang, May 2010 Circle‘s and GreenSeeker‘s NIR light sources are at 880 and 770 nm, respectively. The visible light source in the Crop Circle is at 590 nm (amber) and the GreenSeeker‘s visible light soure is at 660 nm (red). Normalized difference vegetative index (NDVI) was calculated as: (RNIR- Rred or amber)/ (RNIR+Rred or amber), where Rred and Ramber are reflectance in red and the amber regions respectively. Final plant sampling was done in September for final biomass, N uptake and juice extraction. Plants in a 1 m line were harvested manually from the middle two rows, in the center of each subplot on 17th of September in 2008. In 2009, sweet sorghum cultivars were harvested in early September and PPS sorghum cultivars on late September. Seeds were separated from the plants and weighed. Plant samples of the sweet sorghum cultivars, Della and M81E were pressed in a mechanical roller press in order to extract the juice. The brix of the juice for each plot was measured with a refractrometer and the juice was weighed and collected in a bottle and stored in a refrigerator for the further alcohol analysis. Sugar yields were calculated from the brix and the juice yield data (Wortmann et al., 2010) as: SY= JY x Brix x 0.75 Where, SY= Sugar yield, JY= Juice yield and 0.75 as the sugar concentration of juice is 75% of Brix expressed in g kg -1 sugar juice. The dry weight of bagasse and PPS sorghum stalks was recorded after it was dried at 65C for 48 hours. Plant samples were ground to 1 mm and analyzed for N 23

Texas Tech University, Parikshya Lama Tamang, May 2010 using an Leco N analyzer. Similarly, the seeds were dried, ground and analyzed for the N using the Leco N analyzer. Neutral detergent fiber was measured by boiling a sample of the dry plant in a special detergent (soap) under a neutral (pH = 7) condition and filtering the boiled sample through filter paper. The liquid that passes through the filter paper contains starch, sugar, protein and other compounds that are dissolved. The part of the feed sample that does not dissolve remains on the filter paper; this residue is called NDF. After drying, NDF is calculated as a percentage of the original plant sample (Goering and Van Soest, 1970). Neutral detergent fiber digestibility was determined with a basic in vitro wet chemical method. This consisted of incubating a 0.5-g dried, ground plant sample in a CO2 back-pressured 125-mL Erlenmeyer flask containing rumen fluid, buffer medium, and macromineral and micromineral solution (Goering and Van Soest, 1970) for 48 h in a water bath held at 39°C. Critical conditions were adhered to in order to maximize IVdNDF as defined by Grant and Weidner (1992). The 48-h in vitro incubations were terminated by an NDF determination (Goering and Van Soest, 1970) yielding indigestible (id) NDF (IVidNDF). The IVdNDF content of plant sample was determined as the difference between the original NDF and idNDF contents. NDF digestibility (NDFD) = IVdNDF48/NDF*100 where: NDF = neutral detergent fiber 24

Texas Tech University, Parikshya Lama Tamang, May 2010 IVdNDF48= in vitro digestible neutral detergent fiber. NDFD = neutral detergent fiber digestibility Sweet sorghum juice was fermented at room temperature for 5 days. The fermentation vessels were 500 mL Erlenmeyer flasks and the volume of juice used was 200 mL. Dry FerMaxTM yeast of about 0.10 gm was weighed and hydrated with water in an oven at 35oC for one hour and then added to the flask. The pH of the media was measured and adjusted to pH 4.3 with the addition of sulfuric acid. The media was then mixed and left to ferment for 5 days, with CO2 bubbles passing through a tube from the sidearm of the stoppered flask to a beaker of water.

After

fermentation, the samples were collected and stored in a refrigerator for gas chromatograph (GC) analysis.

The ethanol content in the fermented juice was

analyzed by a GC fitted with a flame ionization detector. The column used was a 2.5 m Porapak QS 80/100, the carrier gas was N2 with a 25 ml min-1 flow rate, and the operating temperature was 200 oC. . Cellulosic ethanol yield from PPS sorghum and sweet sorghum bagasse were calculated from the analysis of neutral detergent fiber (NDF) and from NDF digestibility. Lorenz et al., 2009 reported a regression of cellulosic ethanol on NDF and NDFD with an R2 of 0.95.

25

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 1. Physical and chemical characteristics of Acuff sandy clay loam, Spring 2008, Lubbock, TX. Property

Value

Clay (%) †

28

Silt (%) †

18

Sand (%) †

54

Total N (%) †

0.07

pH (1:1 soil:water) †

7.9

CEC (cmolc kg-1) †

17.6

K (µg g-1) †

377

Mehlich 3-P (g kg-1) †

47

NO3-N (kg ha-1) ‡

72

NO3-N (kg ha-1) §

141

Zn (µg g-1) †

1.4

Fe (µg g-1) †

6.1

Ca (µg g-1) †

2157

-1

Mn (µg g ) †

15.7

Mg (µg g-1) †

676

Na (µg g-1) †

40

Cu (µg g-1) †

0.9

† 0-15 cm ‡ 0-60 cm § 0-90 cm

26

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 2. Growing season rainfall and irrigation data in 2008-2009. Lubbock, Texas. 2008 MONTHS

RAINFALL IRRIGATION -----------------------------cm----------------------------

June

5.9

6.3

July

3.1

12.7

August

6.9

0.0

Total

15.9

19

2009 May

0.0

6.3

June

8.6

6.3

July

6.4

6.3

August

0.3

6.3

Total

15.3

25.2

27

Texas Tech University, Parikshya Lama Tamang, May 2010 3.1 Statistical Analysis Analysis of variance was performed using the proc mixed procedure in SAS (SAS 1999) for the dependent variables spring soil NO3-N, dry biomass, Normalized difference vegetative index (NDVI), Plant N concentration, total N uptake, total dry matter, bagasse yield, neutral detergent fiber (NDF), neutral detergent fiber digestibility (NDFD), juice yield, degree brix, ethanol from juice, cellulosic ethanol, total ethanol were analyzed for each year. Replicate and all interactions with replicate were considered random. Culitvar and N rate were treated as fixed effects. The error term for cultivar was replicate X cultivar. The means were separated using Fischer‘s protected least significant difference (LSD) as 0.05 probability level. PROC CORR procedure in SAS (SAS, 1999) was used for correlation analysis of variables and Pearson‘s correlation coefficients were obtained. The following single degree of freedom contrasts were calculated: Within Cultivar SS: Sweet sorghums vs. PPS sorghums Within N rate: Linear and quadratic Proc mixed was also used to regress total ethanol yield on N rate across all cultivars. In this model, N rate and N rate X N rate were considered fixed. Replicate, cultivar, N rate, cultivar X N rate, replicate X cultivar were considered random.

28

Texas Tech University, Parikshya Lama Tamang, May 2010

CHAPTER IV RESULTS AND DISCUSSIONS 4.1 In Season Data

4.1.1 Pre-plant Soil NO3-N Content In 2008, pre-plant soil profile NO3-N was high in all the plots (Fig 1) before the N fertilizer treatments were applied. At the depth of 0.15 m, the N treated plots had the high residual soil NO3-N content of 30 kg ha-1 and at the deeper depth of 0.6 m the soil NO3-N content averaged 65 kg N ha-1. Prior to sorghum cultivation, cotton was grown, so the high residual NO3-N content in the soil might be due to overapplication of N fertilizer to cotton. In spring 2009, the residual soil NO3-N content in all the plots was lower than the previous year, due to 2008 crop uptake (Fig 2). The greatest residual NO3-N contents at depth were with the 134 and 168 kg N ha-1 fertilizer rates, and was relatively low for the other N fertilizer plots.

29

Texas Tech University, Parikshya Lama Tamang, May 2010

NO3-N (kg ha-1) 0

10

20

30

40

50

60

70

80

90 100

0.1

0.2 N rate (kg ha-1) 0.3

Zero 67 101

0.4

Depth (m)

134 168

0.5

0.6

0.7

0.8

0.9

1 Figure 2. Spring pre-plant soil NO3-N content by depth. Lubbock, 2008.

30

Texas Tech University, Parikshya Lama Tamang, May 2010

NO3-N (kg ha-1) 0

10

20

30

40

50

60

70

0.1 0.2 N rate (kg ha-1) Zero

0.3

67 101

0.4

Depth (m)

134 168

0.5 0.6 0.7 0.8 0.9 1

Figure 3. Spring pre-plant soil NO3-N content by depth as affected by N fertilizer rate Lubbock, 2009.

31

Texas Tech University, Parikshya Lama Tamang, May 2010

4.1.2 In-season Biomass Yield Due to wet field conditions in early July, 2008, we were not able to sample sorghum biomass until the V10 stage. In 2008, biomass production at V10 showed no effect of N rate, cultivar or N rate x cultivar interaction (Table 3). Biomass at V10 ranged from 4900 to 7200 kg ha-1. In 2009, there were no cultivar differences in V8 biomass. Across cultivars, however, there was a significant N rate response to dry biomass production at V8. Biomass yields were similar among N-fertilized treatments and were significantly greater than the zero-N plot yields. The zero-N fertilized plot produced biomass of 1376 kg ha-1 (Table 4). However, no cultivar x N rate interaction was observed in mid-season biomass in either year. A significant quadratic relationship was observed at P=0.01 level between biomass production and N rate treatments in 2009. Biomass at V10 in 2008 averaged 5800 kg ha-1, and in 2009 V8 biomass averaged 1800 kg ha-1. This higher biomass yield in 2008 might be because the sorghum plants were harvested later at V10 stages in 2008 while in 2009, the plants were harvested in early July at the V8 stage. Fall army worm infestation limited further biomass production in 2008. In 2009, fall army worm infestation was minimal.

32

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 3. Dry biomass yield of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------5142 5586 6553 5204 5621 a

0 67

4900

5828

6491

6390

5902 a

101

5395

6350

5401

7233

6095 a

134

5114

6350

6221

7193

6220 a

168

5215

5035

5384

5777

5153 A

5830 A

6010 A

6359 A

Means Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

5353 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

33

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 4. Dry biomass yield of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------1326 1531 1158 1489 1376 b

0 67

2105

2099

1736

1981

1980 a

101

1840

2296

2107

1770

2003 a

134

2355

1748

1922

1812

1959 a

168

2369

2043

2116

1739

1999 A

1943 A

1808 A

1758 A

Means Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

*

Linear

**

Quadratic

**

Cultivar x Nitrogen

2067 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

34

Texas Tech University, Parikshya Lama Tamang, May 2010

4.1.3 Normalized Difference Vegetative Index Two different spectroradiometers, Crop Circle and GreenSeeker were used to measure in-season Normalized Difference Vegetative Index (NDVI). In 2008, a significant cultivar response to Crop Circle NDVI was noted however there was no significant N rate response and cultivar X N rate interaction (Table 5). A significant difference between the Crop Circle NDVI from PPS sorghum cultivars and sweet sorghum cultivars was noted. Photoperiod sensitive sorghum had greater Crop Circle NDVI than the sweet sorghum cultivars (0.86 vs. 0.61) (Table 5). Nitrogen fertilizer application did not affect Crop Circle NDVI in 2008 (Table 5). Similarly, GreenSeeker NDVI was also higher in PPS sorghum (0.83) than sweet sorghum cultivars (0.79) in 2008 (Table 6). No significant N rate response and cultivar x N interaction to Green Seeker NDVI was noted in 2008 (Table 6). In 2009, Crop Circle NDVI responded positively to N rate with Sugar Graze Ultra and M81E (Table 7). Della exhibited an inconsistent N rate response. There was no significant cultivar response, N rate response (main effect) and cultivar x N interaction to GreenSeeker NDVI in 2009 (Table 8). However, GreenSeeker NDVI had a significant quadratic relationship to N rate treatment in 2009 (Table 8).

35

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 5. Crop Circle normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------0.69 0.65 0.62 0.59 0.64 a

0 67

0.69

0.68

0.61

0.60

0.65 a

101

0.71

0.70

0.59

0.62

0.66 a

134

0.65

0.71

0.62

0.63

0.65 a

168

0.67

0.64

0.60

0.61

0.63 a

0.68 A

0.68 A

0.61 B

0.61 B

Means Cultivar

**

Sweet vs. PPS sorghums

**

Nitrogen

NS

Linear

NS

Quadratic Cultivar x Nitrogen

NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

36

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 6. GreenSeeker normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------0.84 0.81 0.78 0.74 0.79 a

0 67

0.83

0.84

0.80

0.79

0.81 a

101

0.85

0.84

0.78

0.80

0.82 a

134

0.82

0.86

0.80

0.80

0.82 a

168

0.82

0.81

0.79

0.80

0.80 a

0.83 A

0.83 A

0.79B

0.79 B

Means Cultivar

*

Sweet vs. PPS sorghums

**

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

37

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 7. Crop Circle normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------kg ha-1-----------------------------------0

0.61 a

0.63 b

0.73 a

0.65 ab

0.65

67

0.63 a

0.71 a

0.62 b

0.61 b

0.64

101

0.64 a

0.71 a

0.69 a

0.66 ab

0.68

134

0.62 a

0.68 ab

0.64 ab

0.67 ab

0.65

168

0.61 a

0.71 a

0.70 a

0.69 a

Means

0.62 A

0.69 A

0.68 A

0.66 A

Cultivar Sweet vs. PPS sorghums Nitrogen

NS

Linear

NS

Quadratic

NS

0.68

NS NS

Cultivar x Nitrogen

*

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

38

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 8. GreenSeeker normalized difference vegetative index of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. Cultivar Sugar graze ultra

N rate

Maxigain

Della

M81E

Means

0

----------------------------------Kg ha-1----------------------------------0.64 0.61 0.60 0.65 0.63 a

67

0.71

0.80

0.53

0.62

0.67 a

101

0.68

0.78

0.58

0.70

0.68 a

134

0.68

0.78

0.55

0.72

0.68 a

168

0.73

0.74

0.43

0.70

0.69 A

0.74 A

0.54 A

0.68 A

Means Cultivar Sweet vs. PPS sorghums Nitrogen

NS

Linear

NS

NS NS

Quadratic Cultivar x Nitrogen

0.65 a

** NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

39

Texas Tech University, Parikshya Lama Tamang, May 2010

4.1.4 In-season Plant N Concentration In 2008, a significant N rate response and cultivar x N interaction to plant N concentration was not seen at V10 however. However, significant cultivar response to plant N concentration was observed (Table 9). Plant N concentration was not affected by N fertilizer application across the cultivars. Pandey et al. (2001) reported that for every kg of N applied, total plant N increased by 0.41 kg ha-1 in sorghum variety ‗Sepon-82‘.

Plant N concentration was lower in sweet sorghum cultivars than in PPS

cultivars in 2008. The sweet sorghum cultivars had an average of 2.2 % plant N, while the PPS sorghum cultivars had an average of 2.6 %N (Table 9). In 2009, at V8 a cultivar response to plant N concentration was not observed and there was no significant difference between the plant N concentration in PPS sorghum and sweet sorghum cultivars (Table 10). A significant N rate response and a significant cultivar x N interaction were observed in 2009. With increasing N rate, plant N concentration increased. The zero-N fertilized plots had the lowest plant N concentration of 1.4% across all cultivars (Table 10). A significant quadratic relationship was observed between plant N concentration and N rate treatments. Maxigain had the lowest zero-N plant N concentration at 1.2% N. Plant N concentration at V10 in 2008 (2.4 % N) was higher than in 2009 at V8 (1.9 % N). (Table 9 and10).

40

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 9. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------%-----------------------------------0

2.5

2.2

2.1

2.3

2.3 a

67

2.5

2.8

1.8

2.4

2.4 a

101

2.5

2.7

2.4

2.3

2.5 a

134

2.7

2.5

2.0

2.3

2.4 a

168

2.6

2.8

2.2

2.1

2.4 a

2.6 A

2.6 A

2.1 B

2.3 B

Means Cultivar Sweet vs. PPS sorghums Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

* **

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

41

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 10. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------%-----------------------------------0

1.2 b

1.3 c

1.8 b

1.4 b

1.4 c

67

2.0 a

2.0 b

2.0 a

2.0 a

2.0 b

101

2.0 a

1.9 b

2.2 a

2.1 a

2.0 b

134

2.2 a

2.2 ab

2.1 a

2.1 a

2.1 a

168

2.2 a

2.4 a

2.2 a

2.0 a

Means

1.9 A

1.9 A

2.1 A

1.9 A

Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

**

Linear

**

Quadratic

**

Cultivar x Nitrogen

2.2 a

*

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

42

Texas Tech University, Parikshya Lama Tamang, May 2010

4.1.5 In-season Nitrogen Uptake Nitrogen uptake was measured two times a year, at V8 or V10 and at final harvest. In 2008, significant cultivar response, N rate response (main effect) and N x cultivar response to total N uptake were not observed at V10 in 2008 (Table 11). A linear relationship between total N uptake and N rate treatment was observed in 2009, but not in 2008. However, total N uptake responded quadratically to N rate treatments in both years (Table 11 and 12). In both years, no significant difference between total N uptake in PPS sorghum cultivars and sweet sorghum cultivars across the N treatments was noted. In 2009, at V8 a significant N response was observed but there was no cultivar response and no cultivar x N interaction. Total N uptake increased across the four cultivars with N rate, with the control plots having the lowest total N uptake of 19 kg ha-1 (Table 12). Total N uptake was higher in all cultivars in 2008 than in 2009 at V10, i.e. 138 kg N ha-1 vs. 37 kg N ha-1 respectively (Table 11, 12). This was probably due to luxury N uptake of the high residual soil NO3 (140 kg NO3-N ha-1) in 2008.

43

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 11. Nitrogen uptake of sorghums as affected by cultivar and N fertilizer rate at V10, July 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------127 122 138 116 126 a

0 67

124

162

116

152

139 a

101

136

168

131

160

149 a

134

136

163

124

166

147 a

168

136

140

120

115

132 A

151 A

126 A

142 A

Means Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

NS

Linear

NS

Quadratic

**

Cultivar x Nitrogen

128 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

44

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 12. Nitrogen uptake of sorghums as affected by cultivar and N fertilizer rate at V8, July 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------16 20 21 21 19 b

0 67

41

41

35

40

40 a

101

37

44

46

38

41 a

134

50

38

41

40

42 a

168

52

48

46

35

39A

38 A

38 A

35 A

Means Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

**

Linear

**

Quadratic

**

Cultivar x Nitrogen

45 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

45

Texas Tech University, Parikshya Lama Tamang, May 2010 4.2 Final Harvest Data

4.2.1 Dry Stalks Yield In 2008, the average dry stalks yield was 11,911 kg ha-1, which was lower than the 2009 yield of 14,018 kg ha-1 (Table 13 and 14). Stalks yield increased in 2009 for all the cultivars except Della. A significant difference between stalks yield from PPS sorghum cultivars and sweet sorghum cultivars was noted both in 2008 and 2009. In both years PPS sorghum cultivars produced higher stalks than sweet sorghum cultivars, which is in contrast to the report of Propheter et al. (2010), who reported that the sweet sorghum cultivar M81E produced significantly higher stalks than PPS sorghum in 2008. No significant N response and no cultivar x N interaction to dry stalks yield were observed in 2008. In 2009, a significant main cultivar effect to dry stalks yield was noted. Della had the lowest stalks yield of 10006 kg ha-1 (Table 14). Photoperiod sensitive sorghum produced the highest average dry stalks yield of 16271 kg ha -1 in 2009 (Table 14). A much higher stalks production of 22400 kg ha -1 from PPS sorghum was reported by Propheter et al. (2010) in a study at northeastern Kansas in 2008. Significant N rate response to dry stalks yield was observed in 2009. Stalks yields were similar among all N fertilized plots. Zero-N fertilized plots had the lowest stalks yield across the cultivars of 10909 kg ha-1 (Table14). Dry stalks responded quadratically to N rate treatment only in 2009. Cultivar x N rate interaction to stalks yield was not observed in 2009. 46

Texas Tech University, Parikshya Lama Tamang, May 2010 The dry stalks production from sweet sorghum cultivar M81E ranged from 8000 -15000 kg ha-1 in 2008 and 2009 which is much lower to Propheter et al. (2010) who showed that M81E produced 31100 kg ha -1 in a study at dry land in northeast Kansas. The dry stalks yield reported by Propheter et al. (2010) is much higher than our results, because they received high in-season precipitation ranging from 80-94 cm during their study years, while our water input was 34.9 cm in 2008 and 40.5 in 2009 (Table 2). In another study, Smith and Buxton, (1993) reported sweet sorghum dry stalks yield of 14975 kg ha-1 and 15888 kg ha-1 at Ames, Iowa and Fort Collins, Colorado respectively across two years 1984 and 1985.

47

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 13. Dry stalks yield of sorghums as affected by cultivar and N fertilizer rate, at final harvest, September 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------14011 12330 10487 8033 11215 a

0 67

17374

12143

10024

9527

12267 a

101

16626

13451

9138

8406

11905 a

134

13077

15692

10415

9744

12232 a

168

13264

10835

11414

12238

14870 A

12890 A

10296 B

9590 B

Means Cultivar Sweet vs. PPS sorghums Nitrogen

NS

Linear

NS

Quadratic Cultivar x Nitrogen

NS

11938 a

* NS

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

48

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 14. Dry stalks yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------11790 13639 6919 11289 10909 b

0 67

15728

19255

10979

14091

15013 a

101

17932

17443

10215

15111

15175 a

134

19974

16128

10329

13013

14861 a

168

17174

13645

11590

14114

16520 A

16022 A

10006 C

13524 B

Means Cultivar

**

Sweet vs. PPS sorghums

**

Nitrogen

**

Linear

*

Quadratic Cultivar x Nitrogen

**

14131 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

49

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.3 Total Dry Matter Yield In 2008, there was no significant cultivar response, N rate response, or cultivar x N interaction in total dry matter (TDM) yields at final harvest (Table 15). In 2009, TDM production showed a significant cultivar response. The cultivar Della had the lowest total dry matter yield of 11518 kg ha-1 and the Sugar Graze Ultra had the highest dry matter yield of 16022 kg ha -1 (Table 16). Mirlohi et al. (2000) reported that Sugar graze Ultra produced a TDM yield of 30 t ha-1. Photoperiod sensitive sorghums had higher TDM yields then sweet sorghums in 2009 (Table 16). Significant N rate response was also noted in 2009. Zero-N fertilized plots had the lowest average TDM yield of 11694 kg ha-1 in 2009 (Table 16). Total dry matter yields among the other N-fertilized plots were similar and significantly larger than the zero-N fertilized plots. Similar results were obtained by Ayub et al. (2002) in a study at Faisalabad, Pakistan, who reported significant increase in TDM of the sorghum cultivar JS-263 with increasing N fertilizer rates. A maximum dry matter yield of 22540 kg ha -1 was recorded from plots fertilized with 150 kg N ha-1, and the zero-N plots had 10610 kg ha-1 of TDM. Singh and Singh, (1998) also reported that N application up to 120 mg kg-1 of soil increased the green and dry matter yield of forage sorghum. Total dry matter in our study responded quadratically to N rate in 2009 but not in 2008. No cultivar x N rate interaction was observed in either year. The cultivar M81E produced TDM of 11486 kg ha-1 in 2008 and 15645 kg ha-1 in 2009. This is much less than the report of Wu et al. (2009) who reported that M81E produced TDM 50

Texas Tech University, Parikshya Lama Tamang, May 2010 yields of 18000 – 32000 kg ha-1 at Kansas in 2007. This can again be explained by greater water input in the Kansas study compared to ours. Due to late season infestation of fall army worm, final TDM was lower in 2008 than in 2009. The TDM yield at final harvest was averaged 12952 kg ha -1 in 2008 and 14926 kg ha-1 in 2009 (Table 14 and Table 15). High dry matter yields of 26670 to 29310 kg ha-1 were reported in Northwest Croatia by Macesic et al. (2008), when 48 kg N ha-1 was applied before plowing at 30 cm, followed by two 54 kg N ha -1 topdressings. In that study, sorghum followed soybean.

51

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 15. Total dry matter yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------14011 12330 12435 9329 12026 a

0 67

17374

12143

12611

12199

13582 a

101

16626

13451

11135

9603

12704 a

134

13077

15692

12672

12389

13458 a

168

13264

10835

13967

13910

14870 A

12890 A

12564 A

11486 A

Means Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

NS

Linear

NS

Quadratic Cultivar x Nitrogen

NS

12994 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

52

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 16. Total dry matter yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------11790 13639 8373 12976 11694 b

0 67

15728

19255

12664

101

17932

17443

11821

17555

16188 a

134

19974

16128

11867

15051

15755 a

168

17174

13645

12864

16360

16520 A

16022 A

11518 B

15645 A

Means Cultivar Sweet vs. PPS sorghums Nitrogen

**

Linear

*

Quadratic

**

Cultivar x Nitrogen

16285

15983 a

15011 a

** **

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

53

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.3 Final Plant Nitrogen Concentration In 2008, at plant N concentration at final harvest had significant cultivar response and N rate response. However, no cultivar and N interaction was observed that year. The plant N concentration was greater in PPS sorghum cultivars than in sweet sorghum cultivars in both years. The average plant N concentration in PPS sorghum cultivars was 1.7% while in sweet sorghum cultivars it was 0.98% (Table 17). Lower plant N in sweet sorghum was probably due to N mobilization from leaves to seed. Nitrogen rate resulted in an increase in plant N concentration. Plant N concentration was highest at the 101 kg N ha -1 fertilizer rate in all cultivars, at 1.5% (Table 17). In 2009, final plant N concentration exhibited significant cultivar response, N rate response, and cultivar x interaction. The cultivar M81E had the lowest N concentration at 0.65% (Table 18). Zero-N resulted in the lowest plant N concentration across cultivars (Table 18). Plant N concentration was higher in 2008 than in 2009 at final harvest, i.e. 1.3% vs. 0.7% respectively (Table 17 and18). This was probably due to luxury uptake of the high residual soil NO 3-N in 2008. Plant N concentration responded linearly to N rate in 2008 and 2009.

54

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 17. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------% -----------------------------------0

1.3

1.6

0.8

1.0

1.2 b

67

1.7

1.9

0.9

0.9

1.3 b

101

1.9

1.8

1.1

1.0

1.5 a

134

1.7

1.4

1.0

1.0

1.3 b

168

2.0

1.6

1.1

1.0

1.4 b

1.7 A

1.7 A

1.0 B

1.0 B

Means Cultivar Sweet vs. PPS sorghums Nitrogen

**

Linear

*

Quadratic Cultivar x Nitrogen

** *

NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

55

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 18. Plant N concentration of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------% -----------------------------------0

0.57 c

0.69 b

0.77 a

0.57 b

0.65 c

67

0.69 b

0.67 b

0.64 b

0.63 ab

0.66 c

101

0.76 b

0.75 b

0.74 ab

0.71 a

0.74 b

134

0.74 b

0.86 a

0.80 a

0.67 ab

0.77 ab

168

0.90 a

0.91 a

0.70 ab

0.69 a

0.80 a

Means

0.73 A

0.78 A

0.73 A

0.65 B

Cultivar

*

Sweet vs. PPS sorghums

*

Nitrogen

**

Linear

**

Quadratic

NS

Cultivar x Nitrogen

**

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

56

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.4 Total Nitrogen Uptake Significant cultivar response to total N uptake was observed at final harvest in 2008, but there was no significant N rate response or cultivar x N interaction. Average total N uptake was greater in PPS sorghum cultivars than in sweet sorghum cultivars, at 232 kg ha-1 and 99 kg ha-1, respectively (Table 19). Due to luxury N uptake, total N uptake was greater in all cultivars in 2008 than in 2009, i.e. 166 kg N ha-1 vs. 99 kg N ha-1 respectively (Table 19 and 20). In 2008, total N uptake was 138 kg ha-1 across the cultivars when no N was applied which is comparable to Pritchard and Mason, (1985). They reported that sweet and PPS sorghum extracted more than 100 kg ha -1 when no N was applied. In 2009, total N uptake at final harvest showed significant cultivar response and N rate response across cultivars. However, no cultivar x N interaction to total N uptake was observed at final harvest. Similar to the final harvest of 2008, the PPS sorghum cultivars at final harvest had greater total N uptake than sweet sorghum cultivars in 2009, i.e. 123 kg ha-1 and 74 kg ha-1 (Table 20). Higher total N uptake in PPS sorghum in 2008 and 2009 was related to the higher dry stalks and total dry matter production due to the delay of flowering. Total N uptake increased across all cultivars with the application of N, with the control plots having the lowest total N uptake of 66 kg ha-1 (Table 20).

57

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 19. Total N uptake of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------183 200 92 78 138 a

0 67

289

228

88

79

171 a

101

325

232

105

81

186 a

134

225

214

111

102

163 a

168

252

175

126

129

255 A

210 A

105 B

94 B

Means Cultivar

**

Sweet vs. PPS sorghums

**

Nitrogen

NS

Linear

NS

Quadratic Cultivar x Nitrogen

NS

170 a

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

58

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 20. Total N uptake of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- kg ha-1 ----------------------------------67 93 45 61 66 b

0 67

108

130

65

84

97 a

101

135

130

68

99

108 a

134

149

139

75

82

111 a

168

154

124

76

91

111 a

123 A

123 A

66 B

83 B

Means Cultivar

**

Sweet vs. PS sorghums

**

Nitrogen

**

Linear

**

Quadratic

*

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

59

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.5 Bagasse Yield Bagasse yield in 2008 showed no significant cultivar response, N rate response (main effect) across cultivars or N x cultivar interaction (Table 21). However, a significant linear relationship between N rate and bagasse yield was observed in 2008. In 2009, there was a significant cultivar response to bagasse yield. M81E had significantly higher bagasse yield at 12482 kg ha-1 than Della, which produced 8767 kg ha-1 (Table 22). Bagasse yield exhibited significant quadratic N rate response across all cultivars in 2009. The zero-N rate treatment had the lowest bagasse production of 8052 kg ha-1 (Table 22). However, there was no cultivar x N rate interaction in 2009 too. Bagasse production in 2009 was slightly higher (10624 kg ha 1

) than in 2008 (9658 kg ha-1) (Table 22 and 21).

60

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 21. Bagasse yield of sweet sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2008, Lubbock, TX. Cultivar N rate

Della

M81E

Means

0

10088

8033

9060 b

67

9341

9527

9434 ab

101

8780

8406

8593 b

134

9901

9714

9808 ab

168

10648

12143

11396 a

Means

9752 A

9565 A

Cultivar

NS

Nitrogen

NS

Linear Quadratic Cultivar x Nitrogen

* NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

61

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 22. Bagasse yield of sweet sorghums as affected by cultivar and N fertilizer rate, September 2009, Lubbock, TX. Cultivar N rate

Della

M81E

Means

0

5442

10663

8052 b

67

9766

12939

11353 a

101

9058

13888

11473 a

134

9288

12109

10699 a

168

10280

12814

11547 a

Means

8767 B

12482 A

Cultivar

**

Nitrogen

**

Linear

**

Quadratic

**

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

62

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.6 Neutral Detergent Fiber In 2008, significant cultivar response to Neutral detergent fiber (NDF) was noted. Della had the lowest NDF concentration in 2008 of 51 % (Table 23). This is comparable to the reports of Bean et al., (2006) who reported that Della had 52.7 % NDF. Nitrogen fertilizer resulted in a linear increase in NDF (Table 23). Pholsen and Sornsungnoen, (2004), in contrast, reported that N- K2O rates no had a significant effect on NDF, with a mean NDF of 61%. However, Ayub et al. (2002) reported significant response of N to NDF concentration. The maximum NDF concentration of 66.03% was recorded from the control plots, and it decreased with increased N levels to 63.60% on plots fertilized with 150 kg N ha-1. No cultivar X N rate interaction to NDF was noted this year in our study. In 2009, Della had the highest NDF concentration at 67 % and the PPS sorghums, Maxigain and Sugar Graze Ultra had the lowest NDF at 59 % each (Table 24). This compares to the report of Bean et al. (2005) who reported that Maxigain produced 60.6 % NDF and Sugar Graze Ultra produced 56.3 % NDF. Sorghum NDF was not affected by N fertilizer application in 2009 and there was no cultivar X N rate interaction (Table 24).

63

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 23. Neutral detergent fiber of sorghum stalks as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------%-----------------------------------0

56

55

48

57

54 b

67

56

55

49

56

54 b

101

53

55

51

56

54 b

134

55

57

57

58

57 a

168

55

56

51

59

55 A

56 A

51 B

57 A

Means Cultivar Sweet vs. PPS sorghums Nitrogen

55 b

** NS NS

Linear

*

Quadratic Cultivar x Nitrogen

NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

64

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 24. Neutral detergent fiber of sorghum stalks as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------%-----------------------------------0

60

59

68

62

62 a

67

60

59

66

63

62 a

101

59

59

69

62

62 a

134

58

60

68

63

62 a

168

60

58

64

61

59 C

59 C

67 A

62 B

Means Cultivar Sweet vs. PPS sorghums Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

61 a

** **

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

65

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.7 Neutral Detergent Fiber Digestibility The Neutral Detergent Fiber Digestibility (NDFD) in 2008 showed no significant cultivar response or cultivar x N rate interaction (Table 25). However, NDFD had a significant negative linear relationship with N rate treatment in 2008. In 2009, no significant N rate or cultivar x N rate interaction to NDFD was observed. Significant cultivar response to NDFD was noted in 2009. Della had the lowest NDFD yield, i.e. 58 % in average (Table 26). A significant difference between PPS sorghum NDFD and sweet sorghum NDFD was also noted in 2009 but not in 2008. Neutral detergent fiber digestibility from PPS sorghum cultivars was higher than sweet sorghum cultivar NDFD, i.e. 65% and 61% respectively (Table 26). The average NDFD yield was slightly higher in 2009 than in 2008, i.e. 63 % and 62 % respectively (Table 25 and 26).

66

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 25. Neutral detergent fiber digestibility of sorghums as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------%-----------------------------------0

61

63

68

61

63 a

67

61

62

66

63

63 a

101

61

63

65

62

63 a

134

61

60

57

57

59 a

168

61

61

64

56

61 A

62 A

64 A

60 A

Means Cultivar

NS

Sweet vs. PPS sorghums

NS

Nitrogen

NS

Linear Quadratic Cultivar x Nitrogen

60 a

* NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

67

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 26. Neutral detergent fiber digestibility of sorghums as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------%-----------------------------------0

63

64

58

63

62 a

67

63

69

59

65

64 a

101

66

66

55

65

63 a

134

65

68

56

65

63 a

168

64

68

64

66

64 B

67 A

58 C

65 AB

Means Cultivar Sweet vs. PPS sorghums Nitrogen

NS

Linear

NS

Quadratic Cultivar x Nitrogen

NS

65 a

** **

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

68

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.8 Sweet Sorghum Juice Yield In 2008, cultivar response to juice yield was not observed. Similarly, significant N rate response and cultivar x N rate interaction was also absent (Table 27). In 2009, significant cultivar response to juice yield was noted but no N rate response and cultivar x N interaction was noted (Table 28). The highest juice yield was obtained from M81E at 24216 kg ha-1 and Della had the lowest juice yield at 20274 kg ha-1 (Table 28). The average juice yield was higher in 2009 than in 2008, i.e. 22245 kg ha-1 vs. 17268 kg ha-1 respectively (Table 27 and 28). In 2008, M81E produced an average juice yield of 16000 kg ha-1 and 24000 kg ha-1 in 2009 (Table 27 and 28). Our juice yields were much lower than the report in NE Kansas by Propheter and Staggenborg, (2010), who reported a higher juice yield from M81E of 34800 kg ha-1 at Troy and 30800 kg ha-1 at Manhattan in 2007. The in season cumulative precipitation was above normal at both locations which was 80.2 cm in Troy and 88.3 cm in Manhattan. This higher water input probably resulted in higher juice yields with M81E than in our study. Lack of N response to the juice yield may have been due to the relatively small harvest area. Additionally we observed variability in the efficiency of the roller press.

69

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 27. Juice yield of sweet sorghums as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. Cultivar N rate

Della

M81E

Means

---------------------- kg ha-1 ----------------------------------14975 11456 13216 a

0 67

21080

22319

21700 a

101

17094

10325

13709 a

134

18477

21475

19976 a

168

21026

14454

17740 a

18530 A

16006 A

Means Cultivar

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

70

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 28. Juice yield of sweet sorghums as affected by cultivar and N fertilizer rate, September 2009, Lubbock, TX. Cultivar N rate

Della

M81E

Means

---------------------- kg ha-1 ----------------------------------20452 17794 19123 a

0 67

21637

24366

23002 a

101

20631

27587

24109 a

134

20369

23989

22179 a

168

18279

27341

22810 a

20274 B

24216 A

Means Cultivar

**

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

71

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.9 Brix of Sweet Sorghum Juice In 2008, no effect of cultivar, N rate or cultivar x N interaction to brix was observed (Table 29). Our results are contrast to Pholsen and Sornsungnoen, (2004) who reported that brix value of a forage sorghum increased significantly with the application of N-K2O fertilizer. At the highest N-K2O rates, i.e. brix value ranged from 10.81% to 11.57% for 450-50 N-K2O ha-1 and 650-100 N-K2O ha-1 respectively. In 2009, a significant linear decline in brix with N rate was observed (Tavle 30). There was no cultivar x N interaction in brix (Table 30). The highest brix value was obtained from Della, i.e. 13.7% while M81E had a brix value of 12.7% (Table 30). However, Almodares et al. (2007) reported a brix value of 17.10 % from sweet sorghum cultivar ‗Rio‘ in an experiment carried out in Iran. Similarly, Yadav et al. (2004) reported that maximum brix value of 20.2% and 20.3% with sweet sorghum genotype ‗GSSV-306‘. In that study N fertilizer was split-applied with 30 % at sowing, 35 % at 25 DAS and 35 % at 50 DAS respectively. Brix concentration from the sweet sorghum juice was higher in the year 2009 than in 2008, at 13.2% and 11.9% respectively. Our brix values were lower than reports cited above and from the more humid Brazos Valley (Monk et al., 1984). They reported brix concentrations for the sweet sorghum cultivar Rio of 19.6% and 17.1 % for ‗Brandes‘. This was probably due to lower rain and irrigation input in our study.

72

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 29. Brix of sweet sorghum juice as affected by cultivar and N fertilizer rate, 2008 Lubbock, TX. Cultivar N rate

Della

M81E

Means

-----------------------%---------------------------0

13.2

11.3

12.3 a

67

12.8

10.7

11.7 a

101

11.7

11.2

11.4 a

134

12.4

11.8

12.1 a

168

13.1

11.6

12.3 a

12.6 A

11.3 A

Means Cultivar

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

73

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 30. Brix of sweet sorghum juice as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Della

M81E

Means

-----------------------%---------------------------0

14.2

13.0

13.6 a

67

14.0

13.1

13.5 a

101

13.6

12.9

13.3 a

134

13.0

12.0

12.5 b

168

13.6

12.5

13.1 ab

13.7 A

12.7 B

Means Cultivar

*

Nitrogen

*

Linear Quadratic Cultivar x Nitrogen

* NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

74

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.10 Sweet Sorghum Sugar Yield Sugar yield in 2008 and 2009 showed no cultivar response, no N rate response and no cultivar x N rate interaction (Table 31 and 32). No Sugar yield response to was N fertilizer is in contrast to Gascho et al. (1984) who reported an increase in sugar concentration with increase in N rate. The highest sugar concentration of 13.6% was recorded from the highest N rate of 224 kg ha-1. The sugar yield was higher in 2009 (2192 kg ha -1) than in 2008 (1561 kg ha-1) in average. Smith et al. (1987) reported a higher total sugar yield of sweet sorghum cultivars ranging from 4000 kg ha -1 to 10000 kg ha-1 in continental USA and up to 12000 kg ha-1 at Hawaii. Similarly, in a study at Iowa and Colorado, a higher sugar yield of 6000 kg ha-1 from sweet sorghum cultivars was reported by Smith and Buxton, (1993). As cited earlier, water input in our studies was less than most of the other sweet sorghum studies reported, and this can probably explain our lower sugar yields as well. Lack of N response to the sugar yield in our study may have been due to the relatively small harvest area. Additionally we observed variability in the efficiency of the roller press.

75

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 31. Sugar yield of sweet sorghum juice as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. Cultivar N rate

Della

M81E

Means

---------------------- kg ha-1 ----------------------------------1461 972 1217 a

0 67

1940

2004

1972 a

101

1498

898

1198 a

134

1692

1984

1838 a

168

1914

1254

1584 a

1701 A

1422 A

Means Cultivar

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

76

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 32. Sugar yield of sweet sorghum juice as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. Cultivar N rate

Della

M81E

Means

---------------------- kg ha-1 ----------------------------------2173 1724 1949 a

0 67

2262

2399

2330 a

101

2096

2674

2385 a

134

1992

2164

2078 a

168

1876

2564

2220 a

2080 A

2305 A

Means Cultivar

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

77

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.11 Sweet Sorghum Juice Ethanol Yield In 2008, there was no cultivar response, no N rate response and no cultivar x N interaction to ethanol yield from the juice (Table 33). In 2009, no cultivar response in juice observed. However, significant cultivar x N rate interaction was observed this year (Table 34). The ethanol produced from the juice of M81E responded significantly to N fertilizer rate in 2009. The juice ethanol yield from M81E was significantly lower in zero N rates with 1118 L ha -1 (Table 34). The juice ethanol produced from Della, however did not responded to N fertilizer rates. The average ethanol yield from sweet sorghum juice was higher in 2009 than in 2008, i.e. 1464 L ha-1 and 925 L ha-1 respectively (Table 33 and 34). This reflects the greater juice yields and brix in 2009 compared to 2008.

78

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 33. Juice ethanol yield of sweet sorghums as affected by cultivar and N fertilizer rate, September 2008, Lubbock, TX. Cultivar N rate

Della

M81E

Means

------------------ L ha-1 ----------------0

984

569

777 a

67

902

1013

957 a

101

998

527

763 a

134

1041

1260

1151 a

168

1178

776

977 a

1021 A

829 A

Means Cultivar

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05.

79

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 34. Juice ethanol yield of sorghums as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. Cultivar N rate

Della

M81E

Means

------------------ L ha-1 ----------------0

1418 a

1118 c

1268 a

67

1486 a

1651 ab

1568 a

101

1341 a

1858 a

1600 a

134

1294 a

1471 b

1383 a

168

1294 a

1717 ab

Means

1366 A

1563 A

Cultivar

NS

Nitrogen

NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

1506 a

*

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

80

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.12 Cellulosic Ethanol Yield In 2008, the cellulosic ethanol yield was not affected by N rate, and no cultivar response (main effect) and no cultivar x N interaction was noted. As expected, cellulosic ethanol yield was higher with the PPS sorghums than the sweet sorghums in both years (Table 35 and 36), reflecting the dry stalk yields (Table 13 and 14). Cellulosic ethanol yield was higher in 2009 than in 2008, i.e. 1411 L ha-1 and 1080 L ha-1 respectively, similar to the higher stalks and total dry matter production in 2009 than in 2008. Significant cultivar response and N response to cellulosic ethanol yield was noted and there was no cultivar x N interaction in 2009 (Table 36). Cultivar Della had the lowest cellulosic ethanol yield among the other cultivars, i.e. 866 L ha-1 while Sugar Graze Ultra had the higher cellulosic yield of 1749 L ha -1 (Table 36). Across cultivars, cellulosic ethanol yield responded quadratically to N fertilizer rate in 2009.

81

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 35. Cellulosic ethanol yield of sorghums as affected by cultivar and N fertilizer rate, 2008 Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- L ha-1 ----------------------------------1293 1153 997 741 1046 a

0 67

1550

1104

879

884

1104 a

101

1479

1265

833

796

1093 a

134

1189

1432

813

812

1062 a

168

1189

995

983

1007

1096 a

1382 A

1190 A

901 B

848 B

Means Cultivar Sweet vs. PPS sorghums Nitrogen Linear Quadratic Cultivar x Nitrogen

NS * NS NS NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

82

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 36. Cellulosic ethanol yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

-----------------------------------L ha-1 -----------------------------------0

1191

1398

546

1098

1058 b

67

1556

2159

971

1391

1519 a

101

1892

1899

846

1485

1530 a

134

2047

1798

874

1308

1507 a

168

1769

1493

1092

1409

1441 a

1691 A

1749 A

866 C

1338 B

Means Cultivar

**

Sweet vs. PPS sorghums

**

Nitrogen

**

Linear Quadratic Cultivar x Nitrogen

* ** NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

83

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.13 Total Ethanol Yield Total ethanol yield was higher in 2009 than in 2008 with an average of 2143 L ha-1 vs. 1543 L ha-1 (Table 38). In both years, sweet sorghum cultivars had greater total ethanol production than the PPS sorghum cultivars (Table 37 and 38). Significant N rate response to total ethanol yield was observed in 2009, but not in 2008. There was no cultivar x N interaction to total ethanol yield in 2008 (Table 37). The two sweet sorghum cultivars averaged 1800 L ha -1 of total ethanol yield of 1677 L ha-1 in 2008. This is comparable to Wortmann et al. (2010) who reported that M81E produced the ethanol yield of 1411 L ha -1 at High Plains Agricultural Laboratory (HPAL) in Nebraska on 2007. They reported ethanol yields of 2249 L ha -1 and 2538 L ha-1 from M81E was obtained at West Central Research and Extension Center (WCREC) and South Central Agricultural Laboratory (SCAL) respectively at 2007 in Nebraska. The lower ethanol yield at HPAL might have been be due to the lower in season rainfall (< 350 mm), the high elevation, which reduces the growing season in HPAL compared to other sites. The ethanol yield of around 2300 L ha -1 from M81E at WCREC and SCAL sites in Nebraska compares well with total ethanol yield from M81E in our study in 2009 (Table 38). A total ethanol yield of 2902 L ha-1 was produced from M81E while Della had the lower ethanol yield of 2232 L ha -1 (Table 38). A study conducted by Propheter and Staggenborg, (2010) at Kansas and Manhattan reported a higher yield of ethanol from M81E, i.e. 9656 L ha-1 in 2007 and 10184 L ha-1 in 2008 across the locations. The higher ethanol yield might be because the in-season precipitation was higher ranging from 80-94 cm during their study year, while our study year received 84

Texas Tech University, Parikshya Lama Tamang, May 2010 less water, i.e. 34.9 cm in 2008 and 40.5 in 2009 (Table 2). Similarly, a study by McBee et al. (1988) in Texas reported a high ethanol yield of 3418 L ha -1 from the sweet sorghum cultivar ‗Rio‘. In both years, total ethanol yields from PPS sorghums were significantly less than the sweet sorghum total ethanol yields. This was largely because total ethanol from sweet sorghums consisted of ethanol fermented from the extracted juice, in addition to the cellulosic ethanol estimates. The average total ethanol yield in 2009 was 2143L ha -1, which was higher than the yield in 2008 (1542 L ha-1) The average total ethanol yield in 2009 was comparable to the ethanol yields of 2731, 2923 and 2887 L ha-1 in 2004, 2005 and 2006 respectively in a study conducted by Macesic et al. (2008) in northwest Croatia. Smith et al. (1987) reported that the theoretical ethanol yield ranged from 2129 L ha -1 to 5696 L ha-1 in the continental USA. Smith and Buxton, (1993) reported an average ethanol yield for a two-year study at Iowa and Colorado of 3200 L ha-1. In 2009, total ethanol yield responded quadratically to N fertilizer rate. This allowed us to calculate the optimum N rate, which we will discuss after the N recovery efficiency section.

85

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 37. Total ethanol yield of sorghums as affected by cultivar and N fertilizer rate, 2008, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- L ha-1 ----------------------------------1293 1153 1982 1301 1434 a

0 67

1550

1104

1781

1897

1583 a

101

1479

1265

1831

1324

1475 a

134

1189

1432

1855

2073

1637 a

168

1189

995

2161

1783

1584 a

1382 B

1190 B

1922 A

1677 A

Means Cultivar Sweet vs. PPS sorghums Nitrogen

NS * NS

Linear

NS

Quadratic

NS

Cultivar x Nitrogen

NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05.

86

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 38. Total ethanol yield of sorghums as affected by cultivar and N fertilizer rate at final harvest, September 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- L ha-1 ----------------------------------1191 1398 1964 2216 1692 b

0 67

1556

2159

2457

3042

2304 a

101

1892

1899

2187

3343

2330 a

134

2047

1798

2168

2780

2198 a

168

1769

1493

2386

3127

1691 C

1749 C

2232 B

2902 A

Means Cultivar

**

Sweet vs. PPS sorghums

**

Nitrogen

**

Linear Quadratic Cultivar x Nitrogen

2194 a

* ** NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. * is significant at P = 0.05, ** is significant at P = 0.01.

87

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.14 Nitrogen Recovery Efficiency Nitrogen recovery efficiency was calculated only in 2009, since there was no N response in 2008. No significant N rate response and cultivar x N interaction to recovery efficiency was noted (Table 39). However, there was a significant cultivars response in N recovery. The PPS cultivars had significantly higher N recovery (43 %) than the sweet sorghum cultivars average of 22%. Among the PPS cultivars, Maxigain had higher N recovery (54 %) than Sugar Graze Ultra N recovery of 33% respectively (Table 39). Della and M81E had similar N recovery.

88

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 39. Nitrogen recovery efficiency of sorghum as affected by cultivar and N fertilizer rate, 2009, Lubbock, TX. Cultivar N rate

Maxigain

Sugar graze ultra

Della

M81E

Means

----------------------------------- L ha-1 ----------------------------------0 67

54

50

25

31

40 a

101

60

33

20

34

37 a

134

54

31

20

14

30 a

168

46

16

16

16

54A

33B

20C

24C

Means Cultivar

**

Sweet vs. PPS sorghums

**

Nitrogen

NS

Linear Quadratic Cultivar x Nitrogen

24 a

NS NS NS

Means in a column with the same lower case letter are not significantly different from each other at P = 0.05. Means in a row with the same upper case letter are not significantly different from each other at P = 0.05. NS is not significant at P = 0.05. ** is significant at P = 0.01.

89

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.15 Optimum N Fertilizer Rate Estimates For Maximum Production The agronomic optimum N rate was calculated for total ethanol yields in 2009 using the proc mixed procedure in SAS (Table 40). The estimates for the intercept, linear coefficient, and quadratic coefficients were 1711, 11.438 and

-

0.05279, respectively. The regression/production function was: Y= -0.053x2 + 11.438x + 1711 Where Y is the total ethanol yield (L ha -1) and x is N fertilizer rate (kg ha-1) The optimum N fertilizer rate was calculated by setting the first derivative of the above equation equal to zero, and then solving for x. Optimum N fertilizer rate = linear coefficient/(2 x Quadratic coefficient) =

11.4384/2 x 0.05279 or 108 kg ha-1

Thus, the optimum N fertilizer rate for total ethanol was 108 kg ha -1 in 2009. This compares well with the optimum N rate of 112 kg N ha -1 reported for sweet sorghum in Georgia by Gascho et al. (1984)

90

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 40. Proc mixed procedure for the regression of total ethanol yield from sweet and PPS sorghums (average across cultivars) on nitrogen fertilizer rate, Lubbock, 2009. Covariance Parameter Estimates Cov Parm Estimates Rep Var N_Rate Var x N_Rate Rep x Var Residual

0 304046 0 3573 0 141889 Fit Statistics

-2 Res Log Likelihood AIC (smaller is better) AICC (smaller is better) BIC (smaller is better)

885.9 891.9 892.4 889.2

Solution for Fixed Effects Effect

Estimate

Standard Error

DF

t Value

Pr >/t/

Intercept

1711.29

297.24

3.78

5.76

0.0053

N_Ratelin

11.4384

2.8613

14

4.00

0.0013

N_Ratequad

-0.5279

0.01649

14

-3.20

0.0064

91

Texas Tech University, Parikshya Lama Tamang, May 2010

4.2.16 Optimum N Fertilizer Rate Estimates For Maximum Profit The economic optimum N fertilizer rate (EONR) was calculated by the same quadratic production function (ethanol yield vs. N rate) as in the last section: Y= 0.053x2 + 11.44x + 1711 Instead of setting the first derivative of the function to zero, we set is equal to the N fertilizer price/ethanol price ratio. The final step was the same, solving for x, the N fertilizer rate. We used three ethanol prices from $ 0.25 to $ 1.00 L -1 and three N fertilizer (liquid urea ammonium nitrate, 32 % N) prices ranging from $ 0.70 to $ 1.30 kg N-1. The EONR ranged from 59 to 101 kg N ha-1 (Table 41). The low EONR was associated with the lowest price of ethanol ($ 0.25 L -1) and the most expensive N fertilizer ($ 1.30). The highest EONR of 101 kg N ha -1 was only slightly less than the agronomic optimum of 108 kg N ha-1, and was calculated with $ 0.70 kg urea ammonium nitrate N-1 and $ 1.00 L-1 ethanol prices.

92

Texas Tech University, Parikshya Lama Tamang, May 2010 Table 41.Economic optimum N fertilizer rate (EONR) ethanol production from sweet and photoperiod sensitive sorghums, Lubbock, 2009. Price of Urea Ammonium Nitrate-Nitrogen

Price of Ethanol

EONR

$ kg-1

$ L-1

kg N ha-1

0.70

0.25

81

0.70

0.50

95

0.70

1.00

101

1.00

0.25

70

1.00

0.50

89

1.00

1.00

98

1.30

0.25

59

1.30

0.50

83

1.30

1.00

96

93

Texas Tech University, Parikshya Lama Tamang, May 2010

CHAPTER V CONCLUSIONS High pre-plant soil NO3-N in all the plots in 2008 precluded N rate response to dry stalks yield, TDM, total N uptake, juice yield, juice ethanol, and total ethanol yield. Bagasse yield and final plant N concentration were the only dependent variables to respond to N in 2008. For the 0 - 0.9 m soil profile, the pre-plant soil NO3-N averaged 140 kg N ha-1. In 2009, the residual soil NO3-N was high only with 134 and 168 kg N ha-1 fertilizer rates. A significant N rate response to dry stalks yield, bagasse, plant N, TDM, total N uptake, cellulosic ethanol yield, ethanol from juice (M81E only) and total ethanol yield was observed in 2009. Dry stalks yield and the TDM yield did not respond to N rate fertilizer in 2008 at final harvest, but a significant N rate response to dry stalks yield and TDM yield was observed in 2009. Across the cultivars, the dry stalks yield and TDM yield responded quadratically to N rate in 2009. Bagasse yields responded positively to N rate in both years. Total dry matter was higher in 2009 than in 2008, which averaged 14926 kg ha-1 and 12952 kg ha-1 respectively. The lower yield in 2008 was due to late season infestation of fall army worm. Final total N uptake was higher in 2008 than in 2009, i.e.166 kg N ha-1 and 99 kg N ha-1 respectively. The higher total N uptake in 2008 was due to luxury uptake of high profile soil NO3-N content in 2008. Greater total N uptake in PPS sorghum cultivars than the sweet sorghum cultivars in 2008 and 2009 at final harvest was due to

94

Texas Tech University, Parikshya Lama Tamang, May 2010 the higher dry stalks and total dry matter production by PPS sorghum cultivars in both years at final harvest. In 2008, juice yield averaged 17268 kg ha-1 which was lower than the juice yield in 2009, i.e. 22245 kg ha -1. Juice yield did not respond to N fertilizer and no cultivar x N interaction was noted either year. In 2009, M81E produced a juice yield of 24216 L ha-1, which was greater than the juice produced by Della of 20274 L ha -1. Bagasse yields positively to N fertilizer rate in both years. Sugar yields averaged 1560 and 2200 kg ha-1 for 2008 and 2009, respectively, with no effect of cultivar, N or cultivar x N. The ethanol yield from the sweet sorghum juice was higher in 2009 than in 2008, due to higher brix and sugar production in 2009. Juice ethanol in 2009 averaged 1464 L ha-1 and 925 L ha-1 in 2008. Sweet sorghum juice ethanol yield responded positively to N rate only in case of M81E and only in 2009. No significant N rate response to juice ethanol yield was observed in either year. As, expected, the cellulosic ethanol yield was higher in PPS sorghum cultivars compared to sweet sorghum cultivars in 2008 and 2009, reflecting the higher TDM with no grain. Cellulosic ethanol yield was higher in 2009 than in 2008, i.e. 1411 L ha-1 and 1080 L ha-1 respectively. In 2008, no significant N rate response to cellulosic ethanol yield was noted, however in 2009, cellulosic ethanol yield responded quadratically to N rate. Della had the lowest cellulosic ethanol yield in 2009 which averaged 866 L ha-1. No cultivar x N interaction was noted in both years.

95

Texas Tech University, Parikshya Lama Tamang, May 2010 Total ethanol yield was greater in 2009 than in 2008, i.e. 2143 L ha -1 and 1532 L ha-1 respectively, because of the higher juice ethanol and cellulosic ethanol production in 2009. In both the years, total ethanol yield was higher with sweet sorghum cultivars than PPS sorghum cultivars. The sweet sorghum M81E had the greatest total ethanol yield among all cultivars in 2009 with 2900 L ha-1. No significant N rate response to total ethanol was observed in 2008. However in 2009 total ethanol yield responded quadratically to N rate. The optimum N fertilizer rate for ethanol and TDM across all four cultivars was 108 kg ha-1 in 2009. The optimum N fertilizer for maximum profit in 2009 with $ 0.70 kg N -1 and $0.50 L-1 ethanol was 101 kg ha-1.

96

Texas Tech University, Parikshya Lama Tamang, May 2010

LITERATURE CITED Adamsen, F.J., D.S. Bigelow, and G.R. Scott. 1985. Automated methods for ammonium, nitrate, and nitrite in 2 M KCl-phenylmercuric acetate extracts of soil. Commun. Soil Sci. Plant Anal. 16:883-898. Almodares, A. and A. Sepahi. 1996. Comparison among sweet sorghum cultivars, lines and hybrids for sugar production. Ann. Plant Physiol. 10:50-55. Almodares, A., A. Sepahi., H. Dalilitajary, and R. Gavami. 1994a. Effect of phonological stages on biomass and carbohydrate contents of sweet sorghum cultivars. Ann. Plant Physiol. 8:42-48. Almodares, A., M. Jafarinia, and M.R. Hadi. 2009. The effects of nitrogen fertilizer on chemical composition in corn and sweet sorghum. J. Agric. Environ. Sci. 6(4):441-446. Almodares, A., M.R. Hadi., M. Ranjbar, and R. Taheri. 2007. The effects of nitrogen treatments, cultivars and harvest stages on stalk yield and sugar content in sweet sorghum. Asian J. Plant Sci. 6(2):423-426. Almodares, A., R. Taheri, and S. Adeli. 2008b. Categorization of sweet sorghum cultivars and lines as sweet, dual purpose and grain sorghum. J. Tropical. Agri. 46:62-63. Ashiono, G.B., S. Gatuiku., P. Mwangi, and T.E. Akuja, 2005. Effect of nitrogen and phosphorus application on growth and yield of dual purpose sorghum [Sorghum bicolor (L) Moench], E1291, in the dry highlands of Kenya. Asian J. Plant Sci. 4:379-382. Ayub, M., M.A. Nadeem., A. Tanveer, and A. Husnain. 2002. Effect of different levels of nitrogen and harvesting times on the growth, yield and quality of sorghum fodder. Asian J. Plant Sci. 4:304-307. Bean, B., T. McCollum., K. McCuistion., J. Robinson., B. Villareal., R. VanMeter, and D. Pietsch. 2005. Texas panhandle forage sorghum silage trial. In. http://amarillo.tamu.edu/library/files/brent_bean_publications/forage_sorghum /05silagetrial.pdf Bean, B., T. McCollum., K. McCuistion., J. Robinson., B. Villareal., R. VanMeter, and D. Pietsch. 2006. Texas panhandle forage sorghum silage trial. In. http://amarillo.tamu.edu/library/files/brent_bean_publications/forage_sorghum /06silagetrial.pdf Bernal, J.H., G.E. Navas, and R.B. Clark. 2001. Sorghum nitrogen use efficiency in Colombia. Dev. Plant Soil Sci. 92:66-67. 97

Texas Tech University, Parikshya Lama Tamang, May 2010 Billa, E., D.P. Koullas., B. Monties, and E.G. Koukios. 1997. Structure and composition of sweet sorghum stalk components. Ind. Crops Prod. 6:297-302. Booker, J.D., K.F. Bronson., C.L. Trostle., J.W. Keeling, and A. Malapati. 2007. Nitrogen and phosphorus fertilizer and residual response in cotton-sorghum and cotton-cotton sequences. Agron. J. 99:607-613. Changade, H.S., P.R. Deshmukh., A.H. Deshmukh., P.V. Mohod, and Y.R Sable. 2006. Effect of integrated nutrient levels on juice yield and quality of sweet sorghum. Ann. Plant Physiol. 20(2):247-250. Channappagoudar, B.B., N.R. Biradar., J.B. Patil, and S.M. Hiremath. 2007. Study on morpho-physiological, bio-physical characters and alcohol production in sweet sorghum genotypes. Karnataka J. Agric. Sci. 20(2):234-237. Chen, Y., R.R.S. Shivappa., D. Keswani, and C. Chen. 2007. Potential for agricultural residues and hay for bioethanol production. Appl. Biochem. Biotechnol. 142:276-290. Curt, M.D., J. Fernandez, and M. Martinez. 1995. Productivity and water use efficiency of sweet sorghum [Sorghum bicolor (L.) Moench] cv. ―Keller‖ in relation to water regime‖. Biomass Bioenerg. 8:401-409. Dahlberg, J. 2007. Beyond Grain…Sorghum to ethanol. National Sorghum Producers. In.http://www.sorghumgrowers.com/Ethanol%20Articles/Beyond%20Grain...S orghum%20to%20Ethanol.pdf Doggett, H. 1988. Sorghum. 2nd edition. New York: John Wiley. Farre, I. and J.M. Faci. 2006. Comparative response of maize ( Zea Mays L.) and sorghum [Sorghum bicolor (L.) Moench] to deficit irrigation in a mediterranean environment. Agric. Water Manage. 83:135-143. Galani, N.N., M.H. Lomte, and S.D. Choudhari. 1991. Juice yield and brix as affected by genotype, plant density and N levels in high energy sorghum. Bhartiya Sugar. 16:23-24. Gascho, G.J., R.L. Nichols, and T.P. Gaines. 1984. Growing sweet sorghum as a source of fermentable sugars for energy. Research Bulletin, 315, University of Georgia, Athens, GA. Goering, H. K. and P. J. Van Soest. 1970. Forage Fiber Analyses (Apparatus, Reagents, Procedures, and Some Applications). Agric. Handbook No. 379. ARS-USDA, Washington, DC.

98

Texas Tech University, Parikshya Lama Tamang, May 2010 Grant, R. J. and S. J. Weidner. 1992. Digestion kinetics of fiber: Influence of in vitro buffer pH varied within observed physiological range. J. Dairy Sci. 75:1060– 1068. Leible, L. and G. Kahnt. 1991. Investigations in to the effect of locate on, sowing rate N application, cultivars and harvesting date on yield and composition of sweet sorghum. J. Agron. Crop Sci. 166:8-18. Lemus, R. and J.P. David. 2009. Herbaceous crops with potential for biofuel production in the USA. Perspect. Agric. Vet. Sci. Nutr. Nat. Resour. 4, No. 057. Howell, T.A., J.L. Steiner, A.D. Schneider, S.R. Evett, and J.A. Tolk. 1997. Seasonal and maximum daily evapotranspiration of irrigated wheat, sorghum, and corn—Southern High Plains. Transactions of the ASAE. 40(3):623-634. Jadhav, M.M., B.A. Chougule., U.D. Chavan, and R.N. Adsule. 1994. Assessment of juice quality in the improved sweet sorghum varieties. J. Maharashtra Agric. Univ. 19(2):233-235. Keeney, D.R. and T.H. Deluca. 1992. Biomass as an energy source for the midwestern U.S. Am J. Altern. Agr. 7(3):137-144. Lorenz, A.J., R.B. Anex., A. Isci., J.G. Coors., N. De Leon, and P.J. Weimer. 2009. Forage quality and composition measurements as predictors of ethanol yield from maize (Zea mays L.) stover. Biotech. Biofuels. 2:5 doi:10.1186/17546834-2-5. Macesic, D., D. Uher, and Z. Stafa. 2008. Biomass production and ethanol potential from sweet sorghum in Croatia. In Alps-Adria Scientific Workshop. Stara Lesna, Slovakia. 527-530. Mahmud, K., I. Ahmad, and M. Ayub. 2003. Effect of N and P on the fodder yield and quality of two sorghum cultivars (Sorghum bicolor L.) Int. J. Agric. Biol. 5:6163. Martin, J.H., W.H. Leonard, and D.L. Stamp. 1990. Principles of field crop production. Third ed. Macmillan Publishing Co., Inc. New York. McBee, G.G., F.R. Miller., R.E Dominy, and R.L. Monk. 1986. Quality of sorghum biomass for methanogenesis. In: Symposium Papers, Energy from biomass and waste X. Institute of gas technology. Chicago, Illionois, pp. 251-60.

99

Texas Tech University, Parikshya Lama Tamang, May 2010 McBee, G.G. and F.R. Miller. 1990. Carbohydrate and lignin partitioning in sorghum stems and blades. Agron. J. 82:687-690. McBee, G.G., R.A. Creelman, and F.R. Miller. 1988. Ethanol yield and energy potential of stems from a spectrum of sorghum biomass types. Biomass. 17:201-211. McCollum, T., K. McCuistion, and B. Bean. 2005. Brown midrib and photoperiod sensitive forage sorghums. In: Plains Nutrition Council Spring conference, San Antonio, TX, pp. 36-46. Meli, S.S. 1991. Studies on fertilizer and plant population requirement of sweet sorghum [Sorghum bicolor (L.) Moench] genotypes for increased growth and sugar recovery. Karnataka J. Agric. Sci. 4:75. Miller, F.R. and J.A. Stroup. 2004. Growth and management of sorghums for forage production. In: Proceedings, National Alfalfa Symposium, 13-5 December, San Deigo, CA, UC Cooperative Extension, University of California, Davis 95616. Mirlohi, A., N. Bozorgvar, and M. Bassiri. 2000. Effect of nitrogen rate on growth, forage yield and silage quality of three sorghum hybrids. J. Sci. Technol. Agric. Nat. Resour. 4(2):106-116. Monk, R.L., F.R. Miller, and G.G. McBee. 1984. Sorghum improvement for energy production. Biomass 6:145-385. Montemurro, F., R. Colucci, and N. Martinelli. 2002. Fertilization and N use efficiency in sweet sorghum growing under mediterranean conditions. Rivista di Agronomica. 36(4):313-318. Pandey, R.K., J.W. Maranville, and Y. Bako. 2001. Nitrogen fertilizer response and use efficiency for three cereal crops In Niger. Commun. Soil sci. Plant Anal. 32(9 &10), 1465-1482. Patel, F.B., D.A. Gadekar, and A.G. Bhoite. 1992. Response of forage sorghum varieties to seed rates and nitrogen. J. Maharashtra Agric. Univ. 17(1):150-151. Patel, G.N., P.G. Patel, and J.C. Patel. 1994. Effect of nitrogen and phosphorus on yield quality of forage sorghum (Sorghum bicolor). Indian J. Agron. 39(1):123-125. Patel, J.R. 1998. Response of forage sorghum (sorghum bicolor) to nitrogen and cutting management. Forage Res. 24(1):55-56.

100

Texas Tech University, Parikshya Lama Tamang, May 2010 Patel, J.R., P.C., A.C Sadhu., K.R Thaker, and M.K Gangani. 1994. Response of forage sorghum hybrids to nitrogen. Gujarat Agric. Univ. Res. J. 19(2):5-8. Perlack, R.D., L.L. Wright, A.F., Turhollow, R.L. Graham, BJ. Stokes, and D.C. Erbach. 2005. Biomass as feedstock for bioenergy and bioproducts industry: the technical feasibility of a billion-ton annual supply. Oak Ridge National Laboratory, Oak Ridge, TN. DOE/GO-102005-2135, ORNL/TM-2005/66. Pholsen, S. and N. Sornsungnoen. 2004. Effects of nitrogen and potassium rates and planting distances on growth, yield and fodder quality of a forage sorghum [Sorghum bicolor (L.) Moench]. Pak. J. Biol. Sci. 7(10):1793-1800. Pritchard, K.E. and W.K. Mason. 1985. Nitrogen effects on yield and quality of summer fodder crops. Proceedings of the conference organized by the Australian and New Zealand Societies of Animal Production. pp. 34-35. Propheter, J.L. and S. Staggenborg. 2010. Performance of annual and perennial biofuel crops: Nutrient removal during the first two years. Agron. J. 102:798-805. Propheter, J.L., S.A. Staggenborg., X. Wu, and D. Wang. 2010. Performance of annual and perennial biofuel crops: Yield during the first two years. Agron. J. 102:806-814. Putnam, D.H., W.E. Lueschen., B.K. Kanne, and T.R Hoverstad. 1991. A comparison of sweet sorghum cultivars and maize for ethanol production. J. Prod. Agric. 4(3):377-381. Raj, M.F. and B.K. Patel. 1988. Influence of nitrogen on quality of forage sorghum [Sorghum bicolor (L.) Moench] hybrids. Gujarat Agric. Univ. Res. J. 14(1):6163. Rathke, G.-W. and W. Diepenbrock. 2006. Energy balance of winter oilseed rape (Brassica napus L.) cropping as related to nitrogen supply and preceding crop. Eur. J. Agron. 24:35-44. Rathke, G.-W., B.J. Wienhold, W.W. Wilhelm, and W. Diepenbrock. 2007. Tillage and rotation effect on corn - soybean energy balances in eastern Nebraska. Soil Tillage Res. 97:6-70. Ricaud, R. and A. Arceneaux. 1988. Sweet sorghum for biomass and sugar production in Louisiana. Report of Projects, pp. 167-171. Louisiana Agric.Exper. Stn., Baton Rouge, LA. Raun, W.R. and G.V. Johnson, 1999. Improving nitrogen use efficiency for cereal production. Agron. J. 91:357-363. 101

Texas Tech University, Parikshya Lama Tamang, May 2010 Reddy, B.V.S and R.P. Sanjana. 2003. Sweet sorghum: characteristics and potential. International Sorghum and Millet Newsletter, 44: 26-28. ICRISAT, Andhra Pradesh, India. Reddy, B.V.S., S. Ramesh., P.S. Reddy, B. Ramaiah, P.M. Salimath, and R. Kachapur. 2005. Sweet Sorghum- a potential alternate raw material for bio-ethanol and bio-energy. International Sorghum and Millet Newsletter, 46:79-86. ICRISAT, Andhra Pradesh, India. Reddy, P.S., B.VS. Reddy., A.A. Kumar, and P.S. Rao. 2008. Standardization of nitrogen fertilizer rate for sugar yield optimization in sweet sorghum. Journal of SAT Agricultural Research 6:1-6. Ricaud, R. and A. Arceneaux. 1988. Sweet sorghum for biomass and sugar production in Louisiana. Report of Projects, pp. 167-171. Louisiana Agric.Exper. Stn., Baton Rouge, LA. Rooney, W. L., J. Blumenthal., B. Bean, and J.E. Mullet, 2007. Designing sorghum as a dedicated bioenergy feedstock. Biofuels, Bioprod. Bioref. 1:147-157. Sanderson, M.A., R.M. Jones, J. Ward, and R. Wolfe. 1992. Silage sorghum performance trial at Stephenville. Forage Research in Texas. Report PR-5018. 1992. Texas Agric. Exp. Stn. Stephenville. Sarath, G., R.B. Mitchell., S.E. Satter., D. Funne., J.F. Pedersen, and R.R. Graybosch. 2008. Oppurtunities and roadblocks in utilizing forages and small grains for liquid fuels. J. Ind. Microbiol. Biotechnol. 35:343-354. Singh, K. and B. Singh, 1986. Sweet Sorghum- an ancillary sugar crop. Indian Farming. 36(4):7-8. Singh, Y. and V. Singh, 1998. Response of nitrogen and zinc levels on biomass, quality and chemical composition of forage sorghum [Sorghum bicolor (L.) Moench]. Forage Res. 24(1):21-23. Smith, G.A. and D.R. Buxton. 1993. Temperate zone sweet sorghum ethanol production potential. Bioresour. Technol. 43:71-75. Smith, G.A., M.O. Bagby., R.T. Lewellan., D.L. Doney., P.H. Moore., F.J. Hills., L.G. Campbell., G.J. Hogaboam., G.E. Coe, and K. Freeman. 1987. Evaluation of sweet sorghum for fermentable sugar production potential. Crop Sci. 27:788793. Steduto, P. and M. Unlu. 2000. Comparison of photosynthetic water use efficiency of sweet sorghum at canopy and leaf scales. Turk. J. Agric. For. 24:519-525. 102

Texas Tech University, Parikshya Lama Tamang, May 2010 Steduto, P., N. Katerji., H. Puertos-Molina., M. Unlu., M. Mastrorilli, and G. Rana. 1997. Water-use efficiency of sweet sorghum under water stress conditions Gas-exchange investigations at leaf and canopy scales. Field Crops Res. 54, issue 2-3:221-234. Sumantri, A. and W.D. Lestari. 1997. Yield response of sweet sorghum to nitrogen and phosphate fertilization on alluvial soil. Majalah Penelitian Gula 33(2/3):812. Teli, C.B. 1993. Effect of nitrogen, potassium and crushing period on juice quality and yield of sweet sorghum. Karnataka J. Agric. Sci., 6:319. Turgut, I., U. Bilgili., A. Duman, and E. Acikgoz. 2005. Production of sweet sorghum [Sorghum bicolor (L) Moench] increases with increased plant densities and nitrogen fertilizer levels. Acta Agric. Scand. Sect B. 55:236-240. Undersander, D.J., L.H. Smith., A.R. Kaminski., K.A. Kelling, and J.D. Doll 1990. Sorghum- Forage. In http://www.hort.purdue.edu/newcrop/AFCM/forage.html United States Department of Agriculture. (2008), Data and Statistics. Available from: http://www.usda.gov/wps/portal/!ut/p/_s.7_0_A/7_0_1OB?navid=DATA_STA TISTICS&parentnav=AGRICULTURE&navtype=RT. Accesses February 2008. USDA-National Agricultural Statistics Service. 2008. In http://www.nass.usda.gov/Statistics_by_State/Texas/Publications/Annual_Stati stical_Bulletin/bull08_074.pdf U.S. Department of Energy. 2010. Alternative fuels and advanced vehicles data center.in.http://www.afdc.energy.gov/afdc/ethanol/feedstocks_starch_sugar.ht ml. Wang, D. 2008. K-state engineer researching how sorghum can meet the need for ethanol in agricultural regions where corn‘s potential is nearly exhausted. In http://www.k-state.edu/media/newsreleases/jun08/sorghum61208.html Wang, D., S. Bean., J. McLaren., P. Seib., R. Madl., M. Tuinstra., Y. Shi., M. Lenz., X. Wu, and R. Zhao. 2008. Grain sorghum is a viable feedstock for ethanol production. J. Ind. Microbiol. Biotechnol. 35(5):313-320. Weaver, J.E. 1926. Root development of field crops. First ed. McGraw-Hill Book Company, Inc. New York. Wiedenfeld, R.P. 1984. Nutrient requirement and use efficiency by sweet sorghum. Energ. Agric. 3(1):49-59. 103

Texas Tech University, Parikshya Lama Tamang, May 2010 Wienhold, B.J., G.-W. Rathke, and W.W. Wilhelm. 2006. Energy balance comparison among tillage practices in corn and corn-soybean systems. pp. 244-245. In R.C. Schwartz, R.L. Baumhardt, and J.M. Bell (eds.) Proc. 28th Southern Conservation Systems Conf., Amarillo, Texas. June 26-28, 2006, USDA-ARS Conservation and Production Research Laboratory Report No. 06-1, Bushland, TX. Wortmann, C.S., A.J. Liska., R.B. Ferguson., D.J. Lyon., R.N. Klein, and I. Dweikat. 2010. Dryland performance of sweet sorghum and grain crops for biofuel in Nebraska. Agron. J. 102:319-326. Wu, X., S. Staggenborg., J.L. Propheter., W.L. Rooney., Y. Jianming, and D. Wang. 2009. Features of sweet sorghum juice and their performance in ethanol fermentation. Ind. Crops Prod. 31:164-170. Yadav, S.L., J.R. Ramteke., V.B. Gedam, and M.S. Powar. 2004. Effect of apportioning of nitrogen on juice quality of sweet sorghum genotypes. J. Maharashtra Agric. Univ. 29(2):243-244. Zhao, D., K. R. Reddy., V.G. Kakani, and V.R. Reddy. 2005. Nitrogen deficiency effects on plant growth, leaf photosynthesis and hyperspectral reflectance properties of sorghum. Eur. J. Agron. 22:391-403. Zougmore, R., A. Mando, J. Ringersma, and L. Stroosnijder. 2003. Effect of combined water and nutrient management on runoff and sorghum yield in semi arid Burkina Faso. Soil Use Manage. 19(3):257-264.

104