Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 2001
Publication Date: N/A
Optimal use of animal manures as a crop nutrient source is limited by uncertainty in the amount and timing of nutrient release from land- applied manures. The objective of this study was to determine the amount and dynamics of plant-available nitrogen (N) and phosphorus (P) in soils receiving animal manure or commercial fertilizer. Fifteen soils from seven states were collected to provide a range of soil chemical properties. Beef manure, dairy manure, swine effluent, turkey litter or fertilizer (ammonium polyphosphate) were added to samples of the soils at a target rate of 56 kg P ha**-1 for a total of 27 soil/nutrient source combinations. Amended soils were aerobically incubated under two thermal regimes to simulate field soil water and temperature conditions. Samples were analyzed for plant-available P (Bray 1, Mehlich 3, and Olsen extracts), ammonia-N, and nitrate-N 0, 2, 4, 6, 9, 12, 24, and 52 weeks after treatment. Mineralization of organic N from the different manures varied by manure and soil. For most treatments, significant nitrification began at 2 to 4 weeks and soil nitrate-N concentrations continued to increase on to the end of the study. The percent of the applied P that became plant-available averaged 23.5% but varied significantly by soil, nutrient source, and extract. Maximum available P, averaged across all three extracts, occurred at 6 weeks for fertilizer treatments, 15 to 17 weeks for the beef, dairy, and swine manures, and not until 23.5 weeks for the turkey litter treatments. Results indicate that accurate recommendations for utilizing animal manures as sources of N and P for crop production must consider soil-, manure-, and, for P, soil test-specific information.