Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/13/2001
Publication Date: 9/13/2001
Citation: OLNESS, A.E., VOORHEES, W.B., LOPEZ, D., SWEENEY, C., MATTSON, N., CORDES, J. TAILORING FERTILIZER/NITROGEN APPLICATIONS TO CROP NEEDS: THE USDA-ARS N FERTILIZER DECISION AID. ASSOCIATION OF ANALYTICAL COMMUNITIES. 2001. ABSTRACT P. 71. Interpretive Summary:
Technical Abstract: Nitrogen remains the single most limiting element in crop production. A close correlation exists between nitrate-N in the upper 60 cm of the soil and relative crop yield. Fertilizer N applications realize variable use efficiencies due to the fact that climatic events and microbial mineralization of organic matter affect the amount of N available to the crop. Five variables strongly affect N use efficiency: soil clay content, soil pH, soil temperature, soil bulk density and rainfall. Mathematical models of the effect of each factor were developed using the General Energy Model for Limited Systems, the mathematical engine of the N Fertilizer Decision Aid. These were then combined to predict, a priori, the change in concentration of nitrate in the upper 60 cm of the soil. Field sites were selected which had a range of pH values of 5.8 to 7.9, clay content of 24.2 to 37.3 %, and organic carbon contents from 1.4 to 4.5 %. Field results show that the decision aid can estimate changes in nitrate-N to within 2 t 3 ug g**-1. By determining soil nitrate-N before planting and estimating the amount of nitrate-N formed through microbial mineralization of soil organic matter, the amount of fertilizer N applied can be tailored to soil and environmental situations. This approach results in significant improvement in N fertilizer use efficiency.