|Van Kessel, Jo Ann|
|Reeves Iii, James|
Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: November 5, 2000
Publication Date: N/A
Technical Abstract: Currently most nutrient management plans incorporate a fixed percentage when accounting for available organic N in the first year of manure application. The objectives of this study were to determine the variability in N mineralization of dairy manures and to determine if compositional parameters can be used to predict the available organic N. Dairy manures (n=107) were collected from farms in MD, VA, PA, NY, and CT. Manure compositions ranged from 14 to 38.6 g/kg dry matter, 0.9 to 9.5 kg/cubic meter total N, and 0.3 to 4.7 kg/cubic meter ammonium-N. Manure-amended soil was aerobically incubated at 25 C and concentrations of ammonium N and nitrate N were determined at day 2 and day 56. The manures were highly variable in their N mineralization characteristics, ranging from a net mineralization of 55% to a net immobilization of 29% of the organic N. When the compositional parameters total N, ammonium N, organic N, total C, DM, lignin, neutral detergent fiber, acid detergent fiber, hemicellulose, C/N ratio, and pH were individually regressed against mineralizable organic N, the highest coefficient of determination (r2) was 0.14. A stepwise regression of all 11 variables yielded a maximal r2 of 0.25. These results suggest that the availability of dairy manure organic N is highly variable and that the availability cannot be predicted by simple compositional parameters.