Soil surfactant stops water repellency and preferential flow paths
SoilUse and Management doi: 10.1111/j.1475-2743.2008.00185.x
Soil Use and Management, December 2008, 24, 409–415
Soil surfactant stops water repellency and preferential flow paths K . O o s t i n d i e 1 , L . W . D e k k e r 1 , J . G . W e s s e l i n g 1 & C . J . R i t s e m a 1,2 1
Wageningen University and Research Center, Alterra, Soil Science Center, P.O. Box 47, 6700 AA Wageningen, The Netherlands, and 2Wageningen University and Research Center, Erosion and Soil Water Conservation Group, P.O. Box 47, 6700 AA, Wageningen, The Netherlands
Abstract This study reports the effects of a soil surfactant on reduction and prevention of water repellency and preferential flow paths in a sandy soil of a golf course fairway, located at Bosch en Duin near Utrecht, the Netherlands. The golf course is constructed on inland dunes composed of fine sand with low organic matter content. The topsoil (0–25 cm) of the fairways exhibits an extremely water repellent behaviour resulting in the development of numerous localized dry spots during dry periods in spring and summer. The influence of surfactant treatments on the wetting of the soil was studied by measuring the volumetric water content with a hand-held Time Domain Reflectometry (TDR) device. Actual water repellency was assessed by placing water drops at regular distances on soil cores taken to a depth of 25 cm with a small (1.5 cm diameter) auger at intervals of 25 cm over a distance of 25 m across the untreated and treated parts of the fairway. Surfactant applications resulted in more homogeneous wetting of the soil profile and elimination of actual water repellency in the fairway soil. Treatments significantly increased water uptake and moisture levels of the soil and prevented the development of preferential flow paths. A visible improvement in turf quality and density was evident on the treated part of the fairway.
Keywords: Actual water repellency, water drop penetration time test, Time Domain Reflectometry, critical soil water content, soil surfactant
Introduction Under certain conditions, a soil can become water repellent resulting in changes to hydrological behaviour and impacting water and solute use, plant growth and risk of environmental contamination. The phenomenon of soil water repellency has been recognized in most parts of the world (e.g. DeBano, 2000; Jaramillo et al., 2000) and has been observed in sand, sandy loam, loam, clay, peaty clay, clayey peat and sandy peat soils (Dekker et al., 2005). However, it is most pronounced in coarse textured soils and is common in sandy soils supporting turf or pasture grasses, where it often results in ongoing management problems (Wallis et al., 1989; Cisar et al., 2000). Although water repellency in a soil has several possible origins, numerous researchers agree that it is caused by a Correspondence: L. W. Dekker. E-mail: [email protected] Received August 2008; accepted after revision September 2008
hydrophobic organic coating on the soil particles (Tucker et al., 1990; Hallett et al., 2001). This coating does not necessarily cover the soil particles completely nor is it necessarily very thick. A thin and ⁄ or partial covering of the soil particles can render them water repellent (Bisdom et al., 1993). Additionally, intermixing of hydrophobic particulate organic matter like remnants of roots, leaves and stems with mineral soil particles may also induce severe water repellency (Bisdom et al., 1993; Dekker & Ritsema, 2000). Water repellency is influenced by season and soil water content. In most cases, repellency decreases during wet autumn and winter months and is most severe during dry periods in spring and summer. This seasonal variation is because of soil moisture conditions. Extended dry periods increase the rate at which soils become water repellent. Likewise, extremely wet weather has been found to lessen or even eliminate water repellent behaviour. Research has shown that there is a critical soil water content range for each layer in a potentially water repellent soil below which the soil is water
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science
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410 K. Oostindie et al. repellent and above which the soil is wettable (Dekker et al., 2001; Ziogas et al., 2005). Soil water repellency may dramatically affect field-scale water and solute movement and has often been underestimated (Bauters et al., 2000). Water repellency and its spatial variability have been shown to cause a reduction in infiltration of irrigation and precipitation water which increases the risk of runoff and erosion (Ritsema et al., 1993; Ritsema & Dekker, 1995). Furthermore, rainfall or irrigation that does infiltrate may move preferentially through narrow channels in the soil (preferential flow paths) while the majority of the soil matrix remains dry (Ritsema & Dekker, 1996; Ta¨umer et al., 2005; Wessolek et al., 2008). Soil surfactants have been suggested as a strategy for overcoming the problems of water repellency in soils (Kostka, 2000; Thomas & Karcher, 2000). An important test of the effectiveness of a soil surfactant is the impact on uniformity of distribution of the water in the soil, as well as the effect on infiltration rate and water content. Maintenance of good turf quality (appropriate sward composition and sward colour), and at the same time optimization of irrigation and conservation of water, are important goals for turfgrass managers, especially under dry conditions. Approaches to water conservation include maximizing irrigation efficiency and minimizing the losses of water by surface runoff and leaching or drainage below the rootzone. Soil surfactants may play a role in this. The objective of our study was to investigate the effects of a soil surfactant on infiltration, homogeneity of soil wetting and the elimination of actual soil water repellency in a golf course fairway with relatively thick and extremely water repellent topsoil.
Materials and methods Site description The study was conducted at golf club ‘‘De Pan’’, located at Bosch en Duin, near Utrecht in the Netherlands. The fairways of the golf course, a mix of Festuca spp and Poa annua grasses, on inland dunes of fine sand with less than 3% clay to a depth of more than 2 m, and classified as a Typic Psammaquent (FAO, 2006). An organic matter content (by ignition) of 5–12% w ⁄ w was determined for the surface layer (0–2.5 cm) and 3.5–7% w ⁄ w for the second layer (2.5–5 cm). At 7–12 cm the organic matter content was 2–5% w ⁄ w, while deeper in the profile it further decreased to 1–3% w ⁄ w at 21–26 cm depth. Below this layer the organic matter content was 5 s) were recorded. Measuring the persistence of soil water repellency in classes was considered impractical because of the required time as water drops may stay on soil surfaces for several hours.
Results and discussion
0
20
Frequency (%) 40 60
80
100
Depth (cm) 0 – 1.25 1.25 – 2.5 2.5 – 5 7 – 9.5 9.5 – 12 14 – 16.5 16.5 – 19 21 – 26 WDPT 6h
600 – 3600 s
Figure 2 Relative frequency of the persistence of actual water repellency measured on field moist samples from eight depths of the fairway on 23 October 2003 (n = 35 per depth).
or extremely water repellent (with WDPT often more than 6 h).
Soil water content in the surface layer in 2004 and 2005
Soil water content in the surface layer of the 2003 transect The volumetric soil water content measured in the surface layer (0–5 cm) of the transect on 28 July 2003 ranged between 4 and 38%, as shown in Figure 1. The largest differences often occurred within short distances illustrating the extreme variability of soil water content across this fairway.
Persistence of actual water repellency The top 1.25 cm of the soil profile was completely wettable over the entire distance of the transect on 23 October 2003 (Figure 2). However, at the same time a substantial part of the soil beneath this thin layer displayed extreme water repellency to a depth of 16.5 cm whereas the soil was wettable beneath 19 cm. At the time of sampling, the soil between depths of 1.25 and 16.5 cm was either wettable (WDPT < 5 s)
Compared to the untreated part of the fairway, the soil water content of the surface layer (0–5 cm depth) in the surfactant treated part was distinctly higher and the transect variability was notably lower (29–35% vs. 8–36%) on 16 August 2004, after a total of four surfactant applications (Figure 3). Differences in soil water content and transect variability were also detected between treatments in assessments made on 2, 10 and 27 September 2004. Extreme variability in soil water content of the surface layer occurred over short distances in the untreated part of the fairway, particularly during the summer months in both years (Figure 3). Only slight differences in soil water content of the surface layer were observed between the untreated and treated parts on 8 December 2004 and 15 February 2005 (Figure 3). This recovery is because of the rainy winter period raising soil water content above the critical level.
Figure 1 Volumetric soil water content in the upper 5 cm of the fairway on 28 July 2003, measured in a transect over a distance of 60 m at 0.5 m intervals.
Soil water content (vol.%)
40 35 30 25 20 15 10 5 0
0
10
20
30 Distance (m)
40
50
60
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science, Soil Use and Management, 24, 409–415
412 K. Oostindie et al.
Untreated
50
Untreated
Treated
Treated
16 August, 2004
10 May, 2005
2 September, 2004
7 June, 2005
10 September, 2004
5 July, 2005
40 30 20 10 0 50 40 30 20 10 0 50 40 Soil water content (vol.%)
30 20 10 0 50 40
27 September, 2004
1 August, 2005
8 December, 2004
31 August, 2005
15 February, 2005
14 September, 2005
30 20 10 0 50 40 30 20 10 0 50 40 30 20 10 0 0
5
10
15
20
Distance (m)
25
0
5
10
15
20
25
Distance (m)
Figure 3 Volumetric soil water content in the surface layer (0–5 cm) measured across the untreated (0–12.5 m) and treated (12.5–25 m) parts of the fairway on 12 sampling dates between 16 August 2004 and 14 September 2005.
Only minor variations in surface layer soil water content were observed between surfactant treated and untreated parts of the fairway on 10 May 2005 (Figure 3). By 7
June 2005 severe heterogeneity in soil water content redeveloped in the untreated soil in contrast to the homogeneous water contents that were maintained in the
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science, Soil Use and Management, 24, 409–415
Figure 4 Relationship between the coefficient of variation and the mean soil water content measured in the surface layer (0– 5 cm) of the untreated and treated parts of the fairway on twelve sampling dates.
Coefficient of variation (%)
Elimination of water repellency 413
Untreated
120
Treated 2
R 2 = 0.13
R = 0.84
100 80 60 40 20 0 0
surfactant treated soil. In the untreated area, soil water contents ranged between 4 and 32%, whereas values in the treated part ranged mostly between 28 and 36%. These huge differences in water content between the untreated and treated parts of the fairway were consistently found on all subsequent assessment dates during 2005 (Figure 3). In the untreated part of the fairway, there was a strong negative correlation between the coefficient of variation and the mean soil water content. No such correlation was detected for the surfactant treated part of the fairway, as a result of the low coefficients of variation and the small range of the mean (higher) soil water contents (Figure 4).
Actual soil water repellency Surfactant treatment resulted in the complete remediation of soil water repellency and prevention of its recurrence. On 10 September 2004, most of the soil in the untreated part of the fairway was water repellent. In contrast all 50 soil cores from the treated part which had received the surfactant four times were completely wettable (Figure 5). The transect across the untreated half shows that on 10 September 2004 the actual water repellency consistently started at the surface and ended at a depth between 10 and 22 cm. Interspersed between the water repellent regions were vertically oriented wettable regions, indicating the existence of preferential flow paths. The data from 27 September 2004 reveal a thin wettable surface layer and an increase in the development of preferred flow paths (Figure 5). By 8 December 2004, much of the untreated soil had shifted from repellent to wettable. However, there were still several dry areas where actual water repellency was present. Even on 15 February 2005, we detected locally dry, dusty water repellent sand in the untreated part of the fairway, as illustrated in figure 5, even after a period with numerous rain events (in total 174 mm rain since 8 December 2004). In 2005, large sections of actual water repellent soil were identified in the untreated part of the fairway on all measure-
10
20
40 0 10 30 Mean soil water content (vol.%)
20
30
40
ment dates between 7 June and 14 September, while on these same dates the surfactant treated soil did not show any water repellency in the profile (Figure 5).
Effects of surfactant treatment on plant composition and quality Another interesting observation was that on all sampling dates grass growth, density and colour were obviously better on the surfactant treated part of the fairway compared with the untreated part. The better grass performance of the treated part of the fairway is clearly visible in the aerial photograph taken on 17 July 2005 (Figure 6). Without quantifying our observations, it became clear that the number and composition of grass species was different between the two halves of the fairway. In the untreated part Thousand Leaves Grass, Achillea millefolium (an indicator for soil dryness) often occurred. While this plant was present prior to surfactant treatment, it appeared to decline in the treated part of the fairway, and was only sporadically observed after four surfactant treatments. It was also noted that differences in turf composition occurred as a consequence of surfactant treatment with annual blue grass (Poa annua) gradually being replaced by creeping red fescue (Festuca rubra).
Conclusions Applications of a methyl-capped triblock copolymer soil surfactant on a sand based fairway led to remediation and prevention of soil water repellency, more homogeneous water distribution in the root zone and elimination of preferential flow paths. As a result soil water and solutes would have been less rapidly transported to the subsoil, and remained more accessible to the plant. Therefore, turf quality improved noticeably compared with the untreated part of the fairway. This study indicates that regular surfactant applications leads to multiple benefits: remediation and prevention of soil water repellency, more homogeneous and better soil wetting, more available water in the root zone and improved
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414 K. Oostindie et al.
10 September, 2004 Untreated
7 June, 2005
Treated
Untreated
Treated
0 5 10 15 20 25 27 September, 2004
5 July, 2005
8 December, 2004
1 August, 2005
15 February, 2005
31 August, 2005
10 May, 2005
14 September, 2005
0 5 10 15 20 25 0 Depth (cm)
5 10 15 20 25 0 5 10 15 20 25 0 5 10 15 20 25 0
5
Wettable
10 15 Distance (m)
20
25 0
5
10 15 Distance (m)
20
25
Water repellent
Figure 5 Actual water repellency assessed in the topsoil (0–25 cm) across the untreated (0–12.5 m) and treated (12.5–25 m) parts of the fairway on ten sampling dates between 10 September 2004 and 14 September 2005.
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science, Soil Use and Management, 24, 409–415
Elimination of water repellency 415
Figure 6 Differences in grass quality between the treated and untreated parts of the fairway are clearly visible from the air (courtesy G.F. Lampe).
turf quality, all of crucial importance to golf course managers and players.
References Bauters, T.W.J., Steenhuis, T.S., DiCarlo, D.A., Nieber, J.L., Dekker, L.W., Ritsema, C.J., Parlange, J-Y. & Haverkamp, R. 2000. Physics of water repellent soils. Journal of Hydrology, 231–232, 233–243. Bisdom, E.B.A., Dekker, L.W. & Schoute, J.F. Th. 1993. Water repellency of sieve fractions from sandy soils and relationships with organic material and soil structure. Geoderma, 56, 105–118. Cisar, J.L., Williams, K.E., Vivas, H.E. & Haydu, J.J. 2000. The occurrence and alleviation by surfactants of soil-water repellency on sand-based turfgrass systems. Journal of Hydrology, 231232,352–358. DeBano, L.F. 2000. Water repellency in soils: a historical overview. Journal of Hydrology, 231-232, 4–32. Dekker, L.W. & Ritsema, C.J. 1994. How water moves in a water repellent sandy soil. 1 Potential and actual water repellency. Water Resources Research, 30, 2507–2517.
Dekker, L.W. & Ritsema, C.J. 2000. Wetting patterns and moisture variability in water repellent Dutch soils. Journal of Hydrology, 231-232, 148–164. Dekker, L.W., Doerr, S.H., Oostindie, K., Ziogas, A.K. & Ritsema, C.J. 2001. Water repellency and critical soil water content in a dune sand. Soil Science Society of America Journal, 65, 1667–1674. Dekker, L.W., Oostindie, K. & Ritsema, C.J. 2005. Exponential increase of publications related to soil water repellency. Australian Journal of Soil Research, 43, 403–441. FAO. 2006. World reference base for soil resources. World Soil Resources Reports No. 103. FAO, Rome. Hallett, P.D., Ritz, K. & Wheatley, R.E. 2001. Microbial derived water repellency in golf course soil. International Turfgrass Society Research Journal, 9, 518–524. Jaramillo, D.F., Dekker, L.W., Ritsema, C.J. & Hendrickx, J.M.H. 2000. Occurrence of soil water repellency in arid and humid climates. Journal of Hydrology, 231-232, 105–111. Kostka, S.J. 2000. Amelioration of water repellency in highly managed soils and the enhancement of turfgrass performance through the systematic application of surfactants. Journal of Hydrology, 231-232, 359–368. Ritsema, C.J. & Dekker, L.W. 1995. Distribution flow: a general process in the top layer of water repellent soils. Water Resources Research, 31, 1187–1200. Ritsema, C.J. & Dekker, L.W. 1996. Water repellency and its role in forming preferred flow paths in soils. Australian Journal of Soil Research, 34, 475–487. Ritsema, C.J., Dekker, L.W., Hendrickx, J.M.H. & Hamminga, W. 1993. Preferential flow mechanism in a water repellent sandy soil. Water Resources Research, 29, 2183–2193. Ta¨umer, K., Stoffregen, H. & Wessolek, G. 2005. Seasonal dynamics of preferential flow in a water repellent soil. Vadose Zone Journal, 5, 405–411. Thomas, M.F. & Karcher, D.E. 2000. Incidence and control of localized dry spot on Arkansas putting greens. Research Series-Arkansas Agricultural Experiment Station, 483, 77–79. Tucker, K.A., Karnok, K.J., Radcliffe, D.E., Landry Jr, G., Roncadori, R.W. & Tan, K.H. 1990. Localized dry spots as caused by hydrophobic sands on bentgrass greens. Agronomy Journal, 82, 549–555. Van’t Woudt, B.D. 1959. Particle coatings affecting the wettability of soils. Journal of Geophysical Research, 64, 263–267. Wallis, M.G., Horne, D.J. & McAuliffe, K.W. 1989. A survey of dry patch and its management in New Zealand golf greens. 2. Soil core results and irrigation interaction. New Zealand Turf Management Journal, 3, 15–17. Wessolek, G., Schwa¨rzel, K., Greiffenhagen, A. & Stoffregen, H. 2008. Percolation characteristics of a water-repellent sandy forest soil. European Journal of Soil Science, 59, 14–23. Ziogas, A.K., Dekker, L.W., Oostindie, K. & Ritsema, C.J. 2005. Soil water repellency in north-eastern Greece with adverse effects of drying on the persistence. Australian Journal of Soil Research, 43, 281–289.
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science, Soil Use and Management, 24, 409–415
Soil Use and Management, December 2008, 24, 409–415
Soil surfactant stops water repellency and preferential flow paths K . O o s t i n d i e 1 , L . W . D e k k e r 1 , J . G . W e s s e l i n g 1 & C . J . R i t s e m a 1,2 1
Wageningen University and Research Center, Alterra, Soil Science Center, P.O. Box 47, 6700 AA Wageningen, The Netherlands, and 2Wageningen University and Research Center, Erosion and Soil Water Conservation Group, P.O. Box 47, 6700 AA, Wageningen, The Netherlands
Abstract This study reports the effects of a soil surfactant on reduction and prevention of water repellency and preferential flow paths in a sandy soil of a golf course fairway, located at Bosch en Duin near Utrecht, the Netherlands. The golf course is constructed on inland dunes composed of fine sand with low organic matter content. The topsoil (0–25 cm) of the fairways exhibits an extremely water repellent behaviour resulting in the development of numerous localized dry spots during dry periods in spring and summer. The influence of surfactant treatments on the wetting of the soil was studied by measuring the volumetric water content with a hand-held Time Domain Reflectometry (TDR) device. Actual water repellency was assessed by placing water drops at regular distances on soil cores taken to a depth of 25 cm with a small (1.5 cm diameter) auger at intervals of 25 cm over a distance of 25 m across the untreated and treated parts of the fairway. Surfactant applications resulted in more homogeneous wetting of the soil profile and elimination of actual water repellency in the fairway soil. Treatments significantly increased water uptake and moisture levels of the soil and prevented the development of preferential flow paths. A visible improvement in turf quality and density was evident on the treated part of the fairway.
Keywords: Actual water repellency, water drop penetration time test, Time Domain Reflectometry, critical soil water content, soil surfactant
Introduction Under certain conditions, a soil can become water repellent resulting in changes to hydrological behaviour and impacting water and solute use, plant growth and risk of environmental contamination. The phenomenon of soil water repellency has been recognized in most parts of the world (e.g. DeBano, 2000; Jaramillo et al., 2000) and has been observed in sand, sandy loam, loam, clay, peaty clay, clayey peat and sandy peat soils (Dekker et al., 2005). However, it is most pronounced in coarse textured soils and is common in sandy soils supporting turf or pasture grasses, where it often results in ongoing management problems (Wallis et al., 1989; Cisar et al., 2000). Although water repellency in a soil has several possible origins, numerous researchers agree that it is caused by a Correspondence: L. W. Dekker. E-mail: [email protected] Received August 2008; accepted after revision September 2008
hydrophobic organic coating on the soil particles (Tucker et al., 1990; Hallett et al., 2001). This coating does not necessarily cover the soil particles completely nor is it necessarily very thick. A thin and ⁄ or partial covering of the soil particles can render them water repellent (Bisdom et al., 1993). Additionally, intermixing of hydrophobic particulate organic matter like remnants of roots, leaves and stems with mineral soil particles may also induce severe water repellency (Bisdom et al., 1993; Dekker & Ritsema, 2000). Water repellency is influenced by season and soil water content. In most cases, repellency decreases during wet autumn and winter months and is most severe during dry periods in spring and summer. This seasonal variation is because of soil moisture conditions. Extended dry periods increase the rate at which soils become water repellent. Likewise, extremely wet weather has been found to lessen or even eliminate water repellent behaviour. Research has shown that there is a critical soil water content range for each layer in a potentially water repellent soil below which the soil is water
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science
409
410 K. Oostindie et al. repellent and above which the soil is wettable (Dekker et al., 2001; Ziogas et al., 2005). Soil water repellency may dramatically affect field-scale water and solute movement and has often been underestimated (Bauters et al., 2000). Water repellency and its spatial variability have been shown to cause a reduction in infiltration of irrigation and precipitation water which increases the risk of runoff and erosion (Ritsema et al., 1993; Ritsema & Dekker, 1995). Furthermore, rainfall or irrigation that does infiltrate may move preferentially through narrow channels in the soil (preferential flow paths) while the majority of the soil matrix remains dry (Ritsema & Dekker, 1996; Ta¨umer et al., 2005; Wessolek et al., 2008). Soil surfactants have been suggested as a strategy for overcoming the problems of water repellency in soils (Kostka, 2000; Thomas & Karcher, 2000). An important test of the effectiveness of a soil surfactant is the impact on uniformity of distribution of the water in the soil, as well as the effect on infiltration rate and water content. Maintenance of good turf quality (appropriate sward composition and sward colour), and at the same time optimization of irrigation and conservation of water, are important goals for turfgrass managers, especially under dry conditions. Approaches to water conservation include maximizing irrigation efficiency and minimizing the losses of water by surface runoff and leaching or drainage below the rootzone. Soil surfactants may play a role in this. The objective of our study was to investigate the effects of a soil surfactant on infiltration, homogeneity of soil wetting and the elimination of actual soil water repellency in a golf course fairway with relatively thick and extremely water repellent topsoil.
Materials and methods Site description The study was conducted at golf club ‘‘De Pan’’, located at Bosch en Duin, near Utrecht in the Netherlands. The fairways of the golf course, a mix of Festuca spp and Poa annua grasses, on inland dunes of fine sand with less than 3% clay to a depth of more than 2 m, and classified as a Typic Psammaquent (FAO, 2006). An organic matter content (by ignition) of 5–12% w ⁄ w was determined for the surface layer (0–2.5 cm) and 3.5–7% w ⁄ w for the second layer (2.5–5 cm). At 7–12 cm the organic matter content was 2–5% w ⁄ w, while deeper in the profile it further decreased to 1–3% w ⁄ w at 21–26 cm depth. Below this layer the organic matter content was 5 s) were recorded. Measuring the persistence of soil water repellency in classes was considered impractical because of the required time as water drops may stay on soil surfaces for several hours.
Results and discussion
0
20
Frequency (%) 40 60
80
100
Depth (cm) 0 – 1.25 1.25 – 2.5 2.5 – 5 7 – 9.5 9.5 – 12 14 – 16.5 16.5 – 19 21 – 26 WDPT 6h
600 – 3600 s
Figure 2 Relative frequency of the persistence of actual water repellency measured on field moist samples from eight depths of the fairway on 23 October 2003 (n = 35 per depth).
or extremely water repellent (with WDPT often more than 6 h).
Soil water content in the surface layer in 2004 and 2005
Soil water content in the surface layer of the 2003 transect The volumetric soil water content measured in the surface layer (0–5 cm) of the transect on 28 July 2003 ranged between 4 and 38%, as shown in Figure 1. The largest differences often occurred within short distances illustrating the extreme variability of soil water content across this fairway.
Persistence of actual water repellency The top 1.25 cm of the soil profile was completely wettable over the entire distance of the transect on 23 October 2003 (Figure 2). However, at the same time a substantial part of the soil beneath this thin layer displayed extreme water repellency to a depth of 16.5 cm whereas the soil was wettable beneath 19 cm. At the time of sampling, the soil between depths of 1.25 and 16.5 cm was either wettable (WDPT < 5 s)
Compared to the untreated part of the fairway, the soil water content of the surface layer (0–5 cm depth) in the surfactant treated part was distinctly higher and the transect variability was notably lower (29–35% vs. 8–36%) on 16 August 2004, after a total of four surfactant applications (Figure 3). Differences in soil water content and transect variability were also detected between treatments in assessments made on 2, 10 and 27 September 2004. Extreme variability in soil water content of the surface layer occurred over short distances in the untreated part of the fairway, particularly during the summer months in both years (Figure 3). Only slight differences in soil water content of the surface layer were observed between the untreated and treated parts on 8 December 2004 and 15 February 2005 (Figure 3). This recovery is because of the rainy winter period raising soil water content above the critical level.
Figure 1 Volumetric soil water content in the upper 5 cm of the fairway on 28 July 2003, measured in a transect over a distance of 60 m at 0.5 m intervals.
Soil water content (vol.%)
40 35 30 25 20 15 10 5 0
0
10
20
30 Distance (m)
40
50
60
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science, Soil Use and Management, 24, 409–415
412 K. Oostindie et al.
Untreated
50
Untreated
Treated
Treated
16 August, 2004
10 May, 2005
2 September, 2004
7 June, 2005
10 September, 2004
5 July, 2005
40 30 20 10 0 50 40 30 20 10 0 50 40 Soil water content (vol.%)
30 20 10 0 50 40
27 September, 2004
1 August, 2005
8 December, 2004
31 August, 2005
15 February, 2005
14 September, 2005
30 20 10 0 50 40 30 20 10 0 50 40 30 20 10 0 0
5
10
15
20
Distance (m)
25
0
5
10
15
20
25
Distance (m)
Figure 3 Volumetric soil water content in the surface layer (0–5 cm) measured across the untreated (0–12.5 m) and treated (12.5–25 m) parts of the fairway on 12 sampling dates between 16 August 2004 and 14 September 2005.
Only minor variations in surface layer soil water content were observed between surfactant treated and untreated parts of the fairway on 10 May 2005 (Figure 3). By 7
June 2005 severe heterogeneity in soil water content redeveloped in the untreated soil in contrast to the homogeneous water contents that were maintained in the
ª 2008 The Authors. Journal compilation ª 2008 British Society of Soil Science, Soil Use and Management, 24, 409–415
Figure 4 Relationship between the coefficient of variation and the mean soil water content measured in the surface layer (0– 5 cm) of the untreated and treated parts of the fairway on twelve sampling dates.
Coefficient of variation (%)
Elimination of water repellency 413
Untreated
120
Treated 2
R 2 = 0.13
R = 0.84
100 80 60 40 20 0 0
surfactant treated soil. In the untreated area, soil water contents ranged between 4 and 32%, whereas values in the treated part ranged mostly between 28 and 36%. These huge differences in water content between the untreated and treated parts of the fairway were consistently found on all subsequent assessment dates during 2005 (Figure 3). In the untreated part of the fairway, there was a strong negative correlation between the coefficient of variation and the mean soil water content. No such correlation was detected for the surfactant treated part of the fairway, as a result of the low coefficients of variation and the small range of the mean (higher) soil water contents (Figure 4).
Actual soil water repellency Surfactant treatment resulted in the complete remediation of soil water repellency and prevention of its recurrence. On 10 September 2004, most of the soil in the untreated part of the fairway was water repellent. In contrast all 50 soil cores from the treated part which had received the surfactant four times were completely wettable (Figure 5). The transect across the untreated half shows that on 10 September 2004 the actual water repellency consistently started at the surface and ended at a depth between 10 and 22 cm. Interspersed between the water repellent regions were vertically oriented wettable regions, indicating the existence of preferential flow paths. The data from 27 September 2004 reveal a thin wettable surface layer and an increase in the development of preferred flow paths (Figure 5). By 8 December 2004, much of the untreated soil had shifted from repellent to wettable. However, there were still several dry areas where actual water repellency was present. Even on 15 February 2005, we detected locally dry, dusty water repellent sand in the untreated part of the fairway, as illustrated in figure 5, even after a period with numerous rain events (in total 174 mm rain since 8 December 2004). In 2005, large sections of actual water repellent soil were identified in the untreated part of the fairway on all measure-
10
20
40 0 10 30 Mean soil water content (vol.%)
20
30
40
ment dates between 7 June and 14 September, while on these same dates the surfactant treated soil did not show any water repellency in the profile (Figure 5).
Effects of surfactant treatment on plant composition and quality Another interesting observation was that on all sampling dates grass growth, density and colour were obviously better on the surfactant treated part of the fairway compared with the untreated part. The better grass performance of the treated part of the fairway is clearly visible in the aerial photograph taken on 17 July 2005 (Figure 6). Without quantifying our observations, it became clear that the number and composition of grass species was different between the two halves of the fairway. In the untreated part Thousand Leaves Grass, Achillea millefolium (an indicator for soil dryness) often occurred. While this plant was present prior to surfactant treatment, it appeared to decline in the treated part of the fairway, and was only sporadically observed after four surfactant treatments. It was also noted that differences in turf composition occurred as a consequence of surfactant treatment with annual blue grass (Poa annua) gradually being replaced by creeping red fescue (Festuca rubra).
Conclusions Applications of a methyl-capped triblock copolymer soil surfactant on a sand based fairway led to remediation and prevention of soil water repellency, more homogeneous water distribution in the root zone and elimination of preferential flow paths. As a result soil water and solutes would have been less rapidly transported to the subsoil, and remained more accessible to the plant. Therefore, turf quality improved noticeably compared with the untreated part of the fairway. This study indicates that regular surfactant applications leads to multiple benefits: remediation and prevention of soil water repellency, more homogeneous and better soil wetting, more available water in the root zone and improved
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414 K. Oostindie et al.
10 September, 2004 Untreated
7 June, 2005
Treated
Untreated
Treated
0 5 10 15 20 25 27 September, 2004
5 July, 2005
8 December, 2004
1 August, 2005
15 February, 2005
31 August, 2005
10 May, 2005
14 September, 2005
0 5 10 15 20 25 0 Depth (cm)
5 10 15 20 25 0 5 10 15 20 25 0 5 10 15 20 25 0
5
Wettable
10 15 Distance (m)
20
25 0
5
10 15 Distance (m)
20
25
Water repellent
Figure 5 Actual water repellency assessed in the topsoil (0–25 cm) across the untreated (0–12.5 m) and treated (12.5–25 m) parts of the fairway on ten sampling dates between 10 September 2004 and 14 September 2005.
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Elimination of water repellency 415
Figure 6 Differences in grass quality between the treated and untreated parts of the fairway are clearly visible from the air (courtesy G.F. Lampe).
turf quality, all of crucial importance to golf course managers and players.
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