Assessment of drainage nitrogen losses on a yield-scaled basis

Authors: ZHAO, XU - Chinese Academy Of Sciences; CHRISTIANSON, LAURA - University Of Illinois; Harmel, Daren; PITTELKOW, CAMERON - University Of Illinois

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2016
Publication Date: 9/28/2016
Publication URL: http://handle.nal.usda.gov/10113/63337
Citation: Zhao, X., Christianson, L.E., Harmel, R.D., Pittelkow, C.M. 2016. Assessment of drainage nitrogen losses on a yield-scaled basis. Field Crops Research. 199:156-166.

Interpretive Summary: Subsurface nitrogen (N) losses represent a major environmental concern in agriculture, particularly from fields containing artificial drainage to prevent saturated soil conditions and increase crop production. To develop sustainable intensification strategies and achieve high yields with minimal environmental impacts, N losses are increasingly evaluated with respect to crop productivity on a “yield-scaled” basis, yet little information is available to address the challenge of balancing crop yields and drainage N losses from intensive maize production systems in North America. In the present study, a meta-analysis was conducted using 31 studies with 381 observations from a publicly-available nutrient loss drainage database (Measured Annual Nutrient loads from Agricultural Environments, MANAGE) to address this issue. Results showed that increasing rates of inorganic N fertilizer enhanced yields but had no consistent effect on area- and yield-scaled drainage N losses. In contrast, yield-scaled drainage N losses responded exponentially to N surplus (estimated as inorganic N rate minus above-ground crop N uptake). Fertilizer N rate strategies resulting in zero N surplus rather than maximum yield decreased yield-scaled drainage N losses by 23% without a substantial maize yield penalty. Maize-soybean rotations and silt loam soils had lower yield-scaled drainage N losses compared to continuous maize and clay loam soils, respectively, whereas tillage practices had little impact on yield-scaled drainage N losses. Given the increasing challenge of maintaining profitable maize production systems with reduced environmental costs in the U.S. Midwest, these results suggest that high yields can be achieved with minimal impacts on water quality per unit yield, while also highlighting that climate conditions need to be considered as precipitation occurring during the drainage monitoring period strongly influenced area- and yield-scaled drainage N losses. Moreover, this study provides evidence that considering drainage N losses and crop productivity with a single metric may complement the more conventional approach of evaluating N losses on an area basis to develop sustainable intensification strategies for this region.

Technical Abstract: Subsurface nitrogen (N) losses represent a major environmental concern in agriculture, particularly from fields containing artificial drainage to prevent saturated soil conditions and increase crop production. To develop sustainable intensification strategies and achieve high yields with minimal environmental impacts, N losses are increasingly evaluated with respect to crop productivity on a “yield-scaled” basis, yet little information is available to address the challenge of balancing crop yields and drainage N losses from intensive maize production systems in North America. In the present study, a meta-analysis was conducted using 31 studies with 381 observations from a publicly-available nutrient loss drainage database (Measured Annual Nutrient loads from Agricultural Environments, MANAGE) to address this issue. Results showed that increasing rates of inorganic N fertilizer enhanced yields but had no consistent effect on area- and yield-scaled drainage N losses. In contrast, yield-scaled drainage N losses responded exponentially to N surplus (estimated as inorganic N rate minus above-ground crop N uptake). Regression relationships indicated that N rate strategies resulting in zero N surplus rather than maximum yield decreased yield-scaled drainage N losses by 23% without a substantial maize yield penalty. Maize-soybean rotations and silt loam soils had lower yield-scaled drainage N losses compared to continuous maize and clay loam soils, respectively, whereas tillage practices had little impact on yield-scaled drainage N losses. Given the increasing challenge of maintaining profitable maize production systems with reduced environmental costs in the U.S. Midwest, these results suggest that high yields can be achieved with minimal impacts on water quality per unit yield, while also highlighting that climate conditions need to be considered as precipitation occurring during the drainage monitoring period strongly influenced area- and yield-scaled drainage N losses. Moreover, this study provides evidence that integrating drainage N losses and crop productivity into a single metric may complement the more conventional approach of evaluating N losses on an area basis to develop sustainable intensification strategies for this region.