Submitted to: International Nitrogen Conference
Publication Type: Proceedings
Publication Acceptance Date: October 18, 2001
Publication Date: N/A
Technical Abstract: Nitrogen loss from agricultural systems has created a concern about the potential impact of farming practices on environmental quality. Nitrogen is a critical component in agricultural production. However, there is little understanding of the interactions among crop water use, nitrogen application rates, and soil types. This study was designed to quantify these interactions in corn (Zea mays L.) grown in production size fields in central Iowa on the Clarion-Nicollet-Webster soil association. Seasonal water use varied by soil type and nitrogen application rate. Yield varied with nitrogen application rate with the highest average yield obtained at 100 kg ha**-1. Nitrogen use efficiency decreased with increasing nitrogen application rates with values around 50%. Water use efficiency decreased as nitrogen fertilizer rates increased. Analysis of plant growth patterns showed that in the low organic matter soils with the lower water holding capacities that potential yield was not achieved because of water deficits during the grain filling period. Using precipitation data coupled with daily water use throughout the year the lower organic matter soils showed these soils began to drain earlier in the spring and drained more water throughout the season. The low nitrogen use efficiency in these soils coupled with increased drainage leads to more nitrogen loss from these soils. Improved management decisions have shown that it is possible to couple water use patterns with nitrogen application to increase both water and nitrogen use efficiency.