The effect of calcium superphosphate addition in different stages on the nitrogen fixation and ammonification during chicken manure composting.

Nitrogen losses through ammonia (NH3) emission were an unavoidable issue during chicken manure composting. Calcium superphosphate can be added to effectively limit the emission of NH3. The results show that adding calcium superphosphate in the heating, high temperature and cooling stages reduces ammonia emission by 18.48 %, 28.19 % and 0.91 % respectively. Furthermore, adding calcium superphosphate at high temperature stage increased the ammonium nitrogen content (NH4+-N), reducing the conversion of organic nitrogen (HON) to NH4+-N. Network analysis indicated that adding calcium superphosphate during the high temperature stage reduced NH3-related microorganisms and effectively inhibited ammonification. Moreover, the results of qPCR of the ammonification gene gdh and structural equation model (SEM) verify that adding calcium superphosphate at the high temperature stage reduced ammonification and drove ammonification-related bacterial communities to decrease ammonia emissions. Adding superphosphate at high temperature can effectively increase the nitrogen content and reduce gas pollution during composting.