Effects of nitrification inhibitors DCD and DMPP on maturity, N2O and NH3 emissions during manure composting

In order to reduce N₂O emissions during composting, the effects of different nitrification inhibitors (NI), dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP), on compost maturity, N₂O, and NH₃ emissions were studied under continuous incremental addition. This study used pig manure and corn straw as composting materials, based on the total nitrogen (TN) content of the initial mixture, two treatments were set: DCD (2.5% in the early phase and 5.0% in the maturation phase) and DMPP (0.25% in the early phase and 0.75% in the maturation phase) in a composting experiment. The results showed that adding DCD and DMPP did not affect the compost maturity, with the seed germination index (GI) of final compost reaching 80.76%–97.06%. Before the maturity period of compost, ammonia (NH₃) emissions accounted for 98.5%–99.4% of total emissions. Compared with the control group (CK), the addition of DCD and DMPP in the early stage reduced NH₃ emissions by 8.85% and 12.83%, respectively, by decreasing the ammonification rate. During the mature stage of composting, N₂O emissions account for 95.6%–98.9% of the total emissions. The addition of DCD and DMPP delayed N₂O emissions by 4 and 6 days, respectively, through nitrification inhibition. The DMPP amendment also reduced cumulative N₂O emissions by 54.50% and increased the nitrogen content of the final compost. Correlation analysis showed that N₂O was mainly originated from the denitrification of nitrification substrate (NO₂⁻-N and NO₃⁻-N). This study provides technical support for low-carbon management of agricultural waste.