Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/7/1999
Publication Date: N/A
Technical Abstract: Site-specific application of nitrogen (N) fertilizer is a promising tool for reducing N leaching losses from farm fields without yield reductions. The objective of this research was to develop strategies for variable N applications on loess, Mississippi delta, and claypan soils in Missouri. Constant-rate strips (300 to 600 m long) at different rates of ammonium nitrate (0 to 224 kg N/ha) were applied to corn (Zea mays L.). Indirect evaluations of the spatial effects of N applications on water quality included chlorophyll meter measurements and yield response functions derived from grain harvest data. Direct measurements included root-zone nitrate sampled by buried (90-cm depth) suction lysimeters and residual nitrate in soils after crop removal. Both N application rate and site factors such as landscape position and soil properties were important determiners of N loss. These site factors interacted with climate to influence losses and N uptake.