|Cordes, Jason - MTS SYSTEMS CORPORATION|
|Lopez, Dian - UNIVERSITY OF MINNESOTA|
|Sweeney, Colin - UNIVERSITY OF MINNESOTA|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1997
Publication Date: N/A
Technical Abstract: Non-optimal amounts of fertilizer-N applied to soil represent a potential loss to crop producers or a potential source of Nitrate-N pollution to ground water. A decision aid was developed to predict the amount of supplemental N-fertilizer needed. Near optimal amounts of N-fertilizer needed for grain production are obtained by subtracting existing preplant (0 to 60-cm) and potentially produced nitrate from a threshold level. The decision aid uses rainfall and five soil characteristics: clay content, temperature (T), water content, pH, and bulk density. Values of each factor are calculated and integrated into a coefficient of soil aeration. Mathematical descriptions for T, water content at 1.5 and 0.033 Mpa, and bulk density were developed from literature sources using SAS PROC MODEL procedures. The pH effect is described by a complex sech**2 (pH) function. Soil nitrate is estimated by multiplying the aeration coefficient by the soil N-mineralization potential.