|Lopez, Dian - UNIVERSITY OF MINNESOTA|
|Cordes, Jason - MTS SYSTEMS CORPORATION|
|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: A concentration of nitrate-nitrogen exists beyond which grain yields fail to respond to further fertilizer-N additions. Soil microbial populations produce nitrate through decomposition of soil organic matter. The NO-N produced is determined by a complex interaction of several factors, including temperature and rainfall, soil texture, pH, bulk density and available water holding capacity. Modified energy equations are presented which mathematically describe contributions of each factor. By assuming an intrinsic N-mineralization potential, adjustments can be made for changes in each factor. For maize, changes in soil nitrate during the preplant to the V-5 growth stage (by soil textural class and spring rainfall) suggest that an optimal rainfall exists at which soil aeration is optimized and nitrate production is maximized. Coupling preplant soil nitrate (0 to 60-cm) with prediction of nitrate production, permits tailored N-applications.