Effect of windrow turning and seasonal temperatures on composting of hog manure from hoop structures

A study was undertaken to investigate the effect of windrow turning on comp osting of hoop manure (a mixture of partially decomposed hog manure and cor nstalk). Three series of experiments were conducted: one during summer, one during winter, and one during spring. In all three series bf experiments, windrows were either turned (once a week) or left unturned during the compo sting process, which tasted for 42 days. The effects of windrow turning wer e evaluated by measuring the physicochemical properties (temperature, oxyge n concentration water content, pH, organic matter, and nutrients) of the ho op manure during composting. Turning affected a number of important physica l and chemical parameters such as temperature, oxygen concentrations, and C and mass loss. The temperature of the unturned windrows took longer to dro p to ambient temperature, had lower oxygen concentration, and C and mass lo ss than the turned windrows. These results suggest that the decomposition r ate in turned windrows is much faster than the unturned ones. However, the final product from the two composting treatments (turned and unturned windr ows) was similar in terms of the organic matter, nutrient contents, and C:N ratios. N loss was a major problem during composting of hoop manure. As mu ch as 60% of the N in the hoop manure (both in turned and unturned windrows ) was lost during composting, indicating that composting has significantly reduced the value of hoop manure as N fertilizer. These losses could be att ributed to ammonia volatilization, leaching, and run-off. Overall, composti ng was similar in all three seasons (summer, winter, and spring). This stud y demonstrated that hoop manure could be successfully composted during wint er.