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Title: IMPACT OF MANURE CHARACTERISTICS AND MANAGEMENT ON NITROGEN MINERALIZATION

Author
item DAVIS, J - COLO STATE UNIV
item Vigil, Merle
item JAKUBOWSKI, B - COLO STATE UNIV
item SMITH, G - COLO STATE UNIV

Submitted to: Western Nutrient Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/7/2003
Publication Date: 3/6/2003
Citation: DAVIS, J.G., VIGIL, M.F., JAKUBOWSKI, B.R., SMITH, G.M. IMPACT OF MANURE CHARACTERISTICS AND MANAGEMENT ON NITROGEN MINERALIZATION. WESTERN NUTRIENT MANAGEMENT CONFERENCE PROCEEDINGS. 2003. v. 5. p. 29-33.

Interpretive Summary: Knowledge of the rate and amount of nitrogen (N) released (N mineralization) during the decomposition of manure applied to crop land is needed to accurately recommend manure application rates. Here we measured the rate of N and carbon (C ) release from different animal manures. We found the N content and the fiber concentration of a manure was a good predictor of C release and hence decomposition but was not a reliable predictor of N release. Field studies showed that fall manure application provided more mineralized N than spring application for a summer crop. Crop residue on the soil surface resulted in greater N mineralization rates through we believe increased moisture at the soil surface. Incorporation of manure did not significantly affect N mineralization rates in irrigated systems. We measured greater N mineralization in irrigated systems than in dryland systems.

Technical Abstract: Estimation of N mineralization rates from manure is essential for calculation of agronomic rates of manure application. The objectives of this research include prediction of the rate and amount of N mineralized from manure based on its physical and chemical characteristics, and evaluation of the impact of manure management practices on N mineralization. In incubation studies, mineralization rate was better predicted than the potentially mineralizable N. In addition to the C:N ratio of the manure, its acid detergent fiber content was shown to be an important predictive variable in both laboratory and field studies. Field studies showed that applying manure in the fall provided over six times the amount of mineral N for crop needs at corn's six-leaf stage (the beginning of rapid N uptake) than spring application. Crop residue on the soil surface resulted in greater mineralization rates, probably due to a mulching or insulating effect that resulted in higher soil temperature and greater soil moisture. Incorporation did not significantly affect N mineralization rates in an irrigated system with spring-applied manure. Irrigated plots had higher mineralization rates than that of dryland systems, especially between six-leaf stage and tassel. Although our ability to predict N mineralization rates is improved based on these studies, it is still essential to follow-up on manure application with subsequent soil testing to factor in the remaining uncertainty.