There is minimal information on the nitrogen (N) availability and composition of treated manures. Knowing how N availability differs with manure treatment will result in better N crediting guidelines. Raw dairy manure and anaerobically digested manure were incubated with five typical Wisconsin soils for 112 d. Net N mineralized from the different N sources were compared. Nitrogen mineralization differed by manure type and also by soil. Overall, the digested slurry and the digested separated liquid mineralized more N than the raw slurry. The digested separated solid mineralized significantly less N than the other manures. Net N mineralization as a percent of total N applied was 39, 58, 49, and 17% for raw, digested slurry, digested separated liquid, and digested separated solids, respectively, when averaged over all soils. C:N ratio of manure was found to be the most useful predictor of manure N mineralization.
Soil Science Extension
University of Wisconsin Madison