[Effects of Acidic Materials on the N Transformations During the Composting of Pig Manure and Wheat Straw]

Understanding the effects of acidic materials on the N transformations becomes of critical importance to choose the additives with preserving nitrogen during the manure composting. A 40 d static composting experiment was conducted in the laboratory to explore the effects of acidic materials on changes of temperature, pH, EC (electrical conductivity), GI (germination index), N compounds and TOC (total organic carbon) during the composting of pig manure and wheat straw.Three acidic materials were selected as the additives, including phosphate fertilizer (P), rotten apples (A) and vinegar (V). The results showed that the duration with temperature higher than 50℃ in four treatments all exceeded ten days and reached the health standard of high temperature composting. The addition of phosphate fertilizer delayed the time of the pile entering into the high temperature stage, decreased the pH, and increased the EC during the whole composting. On a mass basis, 53.1%, 36.2%, 46.5% and 41.5% of original amount of N in CK, P, A and V were lost during the first 16 d, but there was still 20% N loss during 16-24 d in P and V treatments. The NH₃-N loss accounted for 26.0%, 11.8%, 21.5% and 20.2% of the N loss. The addition of acidic materials effectively reduced the N loss and the emissions of NH₃, and the phosphate fertilizer showed the best effect. In the end of composting, the GI all exceeded 80%, and met maturity requirements.