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 composting of hoop manure (a mixture of partially decomposed hog manure and cornstalk). 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 composting process, which tasted for 42 days. The effects of windrow turning were evaluated by measuring the physicochemical properties (temperature, oxygen concentration water content, pH, organic matter, and nutrients) of the hoop manure during composting. Turning affected a number of important physical and chemical parameters such as temperature, oxygen concentrations, and C and mass loss. The temperature of the unturned windrows took longer to drop to ambient temperature, had lower oxygen concentration, and C and mass loss than the turned windrows. These results suggest that the decomposition rate in turned windrows is much faster than the unturned ones. However, the final product from the two composting treatments (turned and unturned windrows) 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 much 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 attributed to ammonia volatilization, leaching, and run-off. Overall, composting was similar in all three seasons (summer, winter, and spring). This study demonstrated that hoop manure could be successfully composted during winter.