Nitrogen Availability of Treated and Raw Dairy Manure.

Various manure treatment systems are being implemented on farms across the country. There is minimal information on the nitrogen (N) availability and composition of treated manures. Knowing how N availability differs in treated manure will result in better recommendations for N credits. The objectives of this study were to: 1) determine how much N mineralization differs between raw and treated manures, 2) assess manure compositional effects on N mineralization, and 3) construct a model to predict N mineralization with various manure characteristics. Twenty dairy manures were used in this study and included: raw semi-solid, raw liquid, effluent from mechanically separated slurry, effluent from anaerobically digested slurry, and effluent from separated slurry following anaerobic digestion, composted solids from separated slurry, and composted pack manure. Dairy manure or urea were applied to each of five typical Wisconsin soils at a rate of 150 mg N kg^-1. The treated soils were incubated at 25°C and 40-60% water filled pore space for 0, 3, 7, 14, 28, 56, and 112 days after treatment. Nitrate and ammonium were measured and the N mineralization rates were compared. From this, conclusions were made regarding how N mineralization differed with manure treatments and the effect that manure characteristics (total N or C, C:N ratio, ammonium, neutral detergent fiber, and lignin) had on N mineralization.