Influence of Manure Application Rates and Continuous Corn on Soil‐N1

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Abstract
Manure application to continuous corn (Zea mays L.) should provide some or all of the crop N needs and help maintain or increase soil organic matter. This should be done without damaging the environment by adding excess nutrients to ground or surface waters. A range of factors may influence manure decomposition, and hence N availability to crops. However, application recommendations are usually not site specific. To attempt to deal with site specific considerations, a comparison was made of the effect of manure on soil‐N and crop response to inorganic‐N between similar continuous corn experiments at two different sites.The manure‐N experiments with continuous corn were conducted on both a somewhat poorly drained Panton clay (Typic Ochraqualf) and a well‐drained Calais loam (Typic Fragiorthod). Manure rates of 0, 22, 44, and 66 metric tons/ha/year were combined in factorial arrangement with ammonium nitrate rates of 0, 112, and 224 kg N/ha/year. Comparison of calculated theoretical soil‐N with experimentally determined levels after 5 years and the response of corn to fertializer‐N indicate that mineralization of manure organic‐N, when applied to the Panton clay, was less than when applied to the Calais loam. Thus, manure‐N was less available to the growing crop on the clay and accumulated in the soil at a greater rate than in the loam. The annual manure application rates required to maintain initial soil N levels in Panton clay and Calais loam under continuous corn production were calculated to be 40 to 52 tons/ha respectively. Two mineralization models were examined: Model 1 assumed only the first year manure mineralization rate above native soil organic matter decomposition rate; Model 2 assumed a 5‐year mineralization decay series. Both were effective in predicting final soil‐N levels.

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