Evaluation of Nitrogen Availability from Raw and Treated Dairy Manures

摘要

There is minimal information on the composition of and amounts of potentially available nitrogen from treated manures. Knowing how nitrogen (N) availability differs with manure treatment will result in better N crediting guidelines. Twenty different dairy manures were sampled from five dairy farms and include raw, anaerobically digested before and after liquid-solid separation, non-digested separated liquids and solids, and composted bedded pack manures. The manures were incubated with five representative Wisconsin soils for 112 d. Manure potentially available N (PAN) differed by manure type and by soil. Generally, the treated liquids had significantly more (P<0.05) PAN than the raw liquids and the solids had significantly less (P<0.05) PAN than theraw liquids. N was immobilized in several of the solid manure types evaluated. The manure characteristics best correlated with PAN were acid detergent fiber (ADF) to total N (TN) ratio, neutral detergent fiber (NDF):TN, and NH_4-N:TN (r=-0.94, -0.93, and 0.90, respectively, jp<0.0001). Using linear regression, PAN was best predicted by a model including NH_4-N:TN and organic N concentrations in manure as terms. This equation may assist in refining current University of Wisconsin-Extension first-year Navailability estimates of treated, untreated, solid and liquid manures.