Performance of phosphogypsum and calcium magnesium phosphate fertilizer for nitrogen conservation in pig manure composting

This study investigated the performance of phosphogypsum and calcium magnesium phosphate fertilizer for nitrogen conservation during pig manure composting with cornstalk as the bulking agent. Results show that phosphogypsum increased nitrous oxide (N2O) emission, but significantly reduced ammonia (NH3) emission and thus enhanced the mineral and total nitrogen (TN) contents in compost. Although N2O emission could be reduced by adding calcium magnesium phosphate fertilizer, NH3 emission was considerably increased, resulting in an increase in TN loss during composting. By blending these two additives, both NH3 and N2O emissions could be mitigated, achieving effective nitrogen conservation in composting. More importantly, with the addition of 20% TN of the mixed composting materials, these two additives could synergistically improve the compost maturity and quality.