Microbiological and chemical parameters for evaluating the maturity of spent pig-litter compost

Windrow composting of spent pig litter (partially decomposed pig manure and sawdust) of different initial litter materials was carried out under diffe rent composting strategies to determine potential microbiological and chemi cal parameters that indicate compost maturity. Spent litter was collected f rom pens where the pig-on-litter system was employed, and nine composting p iles were managed under different operating strategies. During composting a nd at maturation, concentrations of NH4+-N, [NO3- + NO2-]-N, extractable P and K, total and water-extractable Cu and Zn, and pH were similar in all pi les regardless of the initial material or operating strategy. The dehydroge nase activity, a microbiological parameter, was also unaffected by initial material or composting strategy. The concentrations of Kjeldahl N, total P and K, C:N ratio, total aerobic heterotroph numbers, ATP content, and micro bial biomass C and N of the composted product, were dependent on the initia l material, composting strategy, or both. Among all parameters measured, de hydrogenase activity, pH, and concentrations of NH4+-N and water-extractabl e Cu and Zn are the simplest, least expensive and most easily measured indi cators of maturity of spent pig litter.