Jeff L. Smith, USDA-ARS, Pullman, WA
Precision Agroecology: Bridging Nitrogen Science with Policy Tabitha T. Brown1 and David R. Huggins2 Department of Crop and Soil Sciences 1Washington State University, Pullman, WA; 2USDA-ARS, Pullman, WA
Introduction
Methods
Rising levels of reactive nitrogen (Nr) in the environment coupled with increasing population positions agriculture as a major contributor for supplying food and ecosystem services to the world (Robertson and Vitousek, 2009). More precise management of N has the potential to improve agroecosystem N use efficiency (NUE) but requires integration with discernable ecosystem processes regulating N cycle transformations that influence the overall fate of N (Jackson and Piper, 1989; Huggins and Pan, 2003; Robertson and Vitousek, 2009). The Palouse region of the Pacific Northwest, USA, is characterized by intricate spatial and temporal variations in soil, ecosystem processes, and socioeconomic factors that create diverse conditions for testing Precision Agroecology concepts (Pan et al., 1993; Huggins and Pan, 2003).
Experimental Site: Washington State University Cook Agronomy Farm near Pullman, WA under long-term no-tillage. Treatments -N Rate x Wheat Density Factorial -N rates of 0, 40, 80, 120 and 160 kg ha-1 and winter wheat (Triticum aestivum) plant density rates of 98, 164, and 240 plants m-2 were imposed across an environmentally heterogeneous field (15 ha). Measurements -Grain yield, available water, NUE and components
Preliminary Results & Insights
Objectives • Evaluate yield-water-NUE relationships among diverse landscape environments to elucidate site-specific processes regulating environmental and economic performance of wheat-based cropping systems;
Next Steps: Process Controls on Nr The preliminary data allow for further development of hypotheses concerning spatial and temporal coupling of processes that influence the fate of N. This information will be critical to advancing science-based, sitespecific decision aid tools that are both policy and farmer relevant (Usherwood and Segars, 2001). Overarching Hypotheses -Hypothesis 1NUE can be improved by tailoring N regime to areas with different hydrologic characteristics, soil organic carbon dynamics and yield potential.
• Investigate the impact of seasonal and landscape-level changes in water availability on N flow and cycling for improving management of N supply and N retention in soil organic matter; and
-Hypothesis 2Coupling sitespecific seeding and N fertilizer rates will use water and N more efficiently, thereby improving N cycling and limiting N losses.
Figure 3. Agroecosystem N cycling relevant to evaluation of soil and plant control of NUE.
Precision Agroecology •Use identified field patterns of biophysical characteristics for studying process controls on site-specific phenomena to develop the concept of Precision Agroecology for use in sustainable agroecosystems and incentive-based Nr policy. b
a c Figure 1. Location map for (a) Palouse region of the Pacific Northwest; (b) Cook Agronomy Farm with N rate map; and (c) typical cross-section of agricultural soils in Palouse region.
a
b
Figure 2. Spatial representation of the field variability in: (a) N required to achieve the greatest yield; and (b) yield obtained at the optimum N rate. Over the entire field, precision N management resulted in applying 62% less (64 kg ha-1) N while improving yield by 794 kg ha-1 compared to conventional uniform N management (103 kg N ha-1). Trends in the data indicated that seeding rate reductions could maintain or increase yield. Insights •Considerable field scale variability exists in yield response to N rate •Farmer adoption of site-specific management could significantly improve NUE thereby reducing N losses to the environment while reducing costs. •Development of science-based decision aids is critical to grower adoption of site-specific management.
The partial success of current US and European policies targeting reactive N species indicate a need for innovative and adaptive management (Manale, 2008). The concept of Precision Agroecology (PA) explicitly recognizes the importance of time and place by combining the principles of precision farming with ecology. The PA approach could also integrate into the structure of existing US programs focused on environmental performance and green payments (e.g., Environmental Quality Incentive Program and Conservation Stewardship Program, respectively).
References Huggins, D.R., Pan, W.L., 2003. Key indicators for assessing nitrogen use efficiency in cereal-based agroecosystems. Journal of Crop Production 8: 157–185. Jackson, W. and J. Piper. 1989. The necessary marriage between ecology and agriculture. Ecology 70(6):1591-1593. Pan, W.L., D.R. Huggins, G.L. Malzer, C.L. Douglas, Jr., and J.L. Smith. 1993, Field heterogeneity in soil-plant nitrogen relationships: implications for site-specific management. In F.J. Perce and E.J. Sadler (eds.) The state of site specific management for agriculture. ASA, CSSA, SSSA, Madison, WI. Robertson, G.P., P.M. Vitousek. 2009. Nitrogen in agriculture: balancing the cost of an essential resource. Annu. Rev. Environ. Resour. 34:13.1-13.29. Usherwood, N.R. and W.I. Segars. 2001. Nitrogen interactions with phosphorous and potassium for optimum crop yield, nitrogen use effectiveness, and environmental stewardship. In Galloway et al. (Eds) Optimizing nitrogen management in food and energy production and environmental protection: Proceedings of the 2nd International Nitrogen Conference on Science and Policy. The Scientific World (2001) October 14-18. 2001. Potomac, MD. pp. 57-60.
Acknowledgments: David Uberuaga, Research Technician with USDA-ARS, Pullman, WA for N rate data, field assistance with plant density experiments, and graphics; Jeff L. Smith, USDA-ARS, Pullman, WA; Chad Kruger, and C. Kent Keller, Washington State University, Pullman, WA; Center for Sustaining Agriculture and Natural Resources, Puyallup, WA.
Introduction
Methods
Rising levels of reactive nitrogen (Nr) in the environment coupled with increasing population positions agriculture as a major contributor for supplying food and ecosystem services to the world (Robertson and Vitousek, 2009). More precise management of N has the potential to improve agroecosystem N use efficiency (NUE) but requires integration with discernable ecosystem processes regulating N cycle transformations that influence the overall fate of N (Jackson and Piper, 1989; Huggins and Pan, 2003; Robertson and Vitousek, 2009). The Palouse region of the Pacific Northwest, USA, is characterized by intricate spatial and temporal variations in soil, ecosystem processes, and socioeconomic factors that create diverse conditions for testing Precision Agroecology concepts (Pan et al., 1993; Huggins and Pan, 2003).
Experimental Site: Washington State University Cook Agronomy Farm near Pullman, WA under long-term no-tillage. Treatments -N Rate x Wheat Density Factorial -N rates of 0, 40, 80, 120 and 160 kg ha-1 and winter wheat (Triticum aestivum) plant density rates of 98, 164, and 240 plants m-2 were imposed across an environmentally heterogeneous field (15 ha). Measurements -Grain yield, available water, NUE and components
Preliminary Results & Insights
Objectives • Evaluate yield-water-NUE relationships among diverse landscape environments to elucidate site-specific processes regulating environmental and economic performance of wheat-based cropping systems;
Next Steps: Process Controls on Nr The preliminary data allow for further development of hypotheses concerning spatial and temporal coupling of processes that influence the fate of N. This information will be critical to advancing science-based, sitespecific decision aid tools that are both policy and farmer relevant (Usherwood and Segars, 2001). Overarching Hypotheses -Hypothesis 1NUE can be improved by tailoring N regime to areas with different hydrologic characteristics, soil organic carbon dynamics and yield potential.
• Investigate the impact of seasonal and landscape-level changes in water availability on N flow and cycling for improving management of N supply and N retention in soil organic matter; and
-Hypothesis 2Coupling sitespecific seeding and N fertilizer rates will use water and N more efficiently, thereby improving N cycling and limiting N losses.
Figure 3. Agroecosystem N cycling relevant to evaluation of soil and plant control of NUE.
Precision Agroecology •Use identified field patterns of biophysical characteristics for studying process controls on site-specific phenomena to develop the concept of Precision Agroecology for use in sustainable agroecosystems and incentive-based Nr policy. b
a c Figure 1. Location map for (a) Palouse region of the Pacific Northwest; (b) Cook Agronomy Farm with N rate map; and (c) typical cross-section of agricultural soils in Palouse region.
a
b
Figure 2. Spatial representation of the field variability in: (a) N required to achieve the greatest yield; and (b) yield obtained at the optimum N rate. Over the entire field, precision N management resulted in applying 62% less (64 kg ha-1) N while improving yield by 794 kg ha-1 compared to conventional uniform N management (103 kg N ha-1). Trends in the data indicated that seeding rate reductions could maintain or increase yield. Insights •Considerable field scale variability exists in yield response to N rate •Farmer adoption of site-specific management could significantly improve NUE thereby reducing N losses to the environment while reducing costs. •Development of science-based decision aids is critical to grower adoption of site-specific management.
The partial success of current US and European policies targeting reactive N species indicate a need for innovative and adaptive management (Manale, 2008). The concept of Precision Agroecology (PA) explicitly recognizes the importance of time and place by combining the principles of precision farming with ecology. The PA approach could also integrate into the structure of existing US programs focused on environmental performance and green payments (e.g., Environmental Quality Incentive Program and Conservation Stewardship Program, respectively).
References Huggins, D.R., Pan, W.L., 2003. Key indicators for assessing nitrogen use efficiency in cereal-based agroecosystems. Journal of Crop Production 8: 157–185. Jackson, W. and J. Piper. 1989. The necessary marriage between ecology and agriculture. Ecology 70(6):1591-1593. Pan, W.L., D.R. Huggins, G.L. Malzer, C.L. Douglas, Jr., and J.L. Smith. 1993, Field heterogeneity in soil-plant nitrogen relationships: implications for site-specific management. In F.J. Perce and E.J. Sadler (eds.) The state of site specific management for agriculture. ASA, CSSA, SSSA, Madison, WI. Robertson, G.P., P.M. Vitousek. 2009. Nitrogen in agriculture: balancing the cost of an essential resource. Annu. Rev. Environ. Resour. 34:13.1-13.29. Usherwood, N.R. and W.I. Segars. 2001. Nitrogen interactions with phosphorous and potassium for optimum crop yield, nitrogen use effectiveness, and environmental stewardship. In Galloway et al. (Eds) Optimizing nitrogen management in food and energy production and environmental protection: Proceedings of the 2nd International Nitrogen Conference on Science and Policy. The Scientific World (2001) October 14-18. 2001. Potomac, MD. pp. 57-60.
Acknowledgments: David Uberuaga, Research Technician with USDA-ARS, Pullman, WA for N rate data, field assistance with plant density experiments, and graphics; Jeff L. Smith, USDA-ARS, Pullman, WA; Chad Kruger, and C. Kent Keller, Washington State University, Pullman, WA; Center for Sustaining Agriculture and Natural Resources, Puyallup, WA.
