Effects of aeration and moisture during windrow composting on the nitrogenfertilizer values of dairy waste composts

The objective of this work was to evaluate the effects of turning and moist ure addition during windrow composting on the N fertilizer values of dairy waste composts. Composted-dairy wastes were sampled from windrow piles, whi ch received four treatments in a 2x2 factorial of turning (turning vs, no t urning) and moisture addition (watering vs. no watering) at two stages of m aturity (mature vs, immature). Composts were characterized for their chemic al properties. An 84-day laboratory incubation of soils with addition of th e composts at two levels was conducted to evaluate the inorganic N accumula tion patterns from the variously treated composts. Chemical analyses of var iously treated composts did not differ between compost treatments or maturi ty In contrast, the inorganic N accumulation patterns differed between soil s that received immature versus mature turned composted-dairy wastes. The r esults suggested that turning was a more important factor than moisture add ition affecting the composting process. There was no significant difference in inorganic N accumulation patterns among soils that received different i mmature composts, while the N accumulation patterns observed for soils that received different mature composts depended on compost treatments. Soils a mended with mature composts treated by frequent turning had higher N minera lization potentials (N-0), mineralization rate constants (K), and initial p otential rates (N0K) in comparison to soils with composts that had not been turned. Soils with mature composts treated by watering had a higher N-0, l ower K, and therefore similar N0K when compared to soils with composts that had not been watered. Soils that received mature composts treated by water ing and frequent turning had higher N mineralization potentials and N-0 to total organic N ratios than soil alone, which suggested that intensive mana gement of composting would ensure positive N fertilizer values of dairy was te composts, if the appropriate composting duration is completed. (C) 1999 Elsevier Science B.V.