Estimating Yield and Yield Response using Computer Simulation of Plant Available Nitrogen from Soil Organic Matter and Manure

Abstract

The amount of organic N mineralized as plant available nitrogen (PAN) from soil organic matter (SOM) during a crop growing season has proved difficult to assess using traditional soil testing. It was the objective of this study to evaluate the potential for computer simulation in the estimation PAN from SOM during the growing season. A secondary objective was to evaluate this approach as a way to identify soils where crops would be non‐responsive to fertilizer N. Plant available N from SOM was estimated using a simple, first‐order kinetic equation. Plant available N from manure was estimated using the computer model, DECOMPOSITION. Plant available N from the previous crop and from preplant fertilizer N were taken from published data. No additional fertilizer N was applied. Corn (Zea mays L.) yield was significantly related to total PAN (sum of SOM N, manure N, crop residue N, and preplant N) and the response of corn to total PAN was typical of previously published values. Total PAN was not a good predictor of soils where corn was nonresponsive to fertilizer N, while a history of manure applications was a good predictor of nonresponsiveness.