Effects of Pig Manure Compost Application Timing (Spring/Autumn) on N2O Emissions and Maize Yields in Northeast China

Animal manure application is widely recognized for its agronomic benefits in enhancing soil fertility and crop productivity through organic matter enrichment and nutrient supply, but the critical application time governing its greenhouse gas emission trade-offs remains unresolved. The objective of this study was to investigate the effects of pig manure compost application timing on nitrous oxide (N2O) emissions and maize yields in Northeast China through a four-year field experiment. The treatments included: (1) inorganic fertilizers (NPK); (2) NPK plus pig manure compost applied in spring (NPK-MS); and (3) NPK plus pig manure compost applied in autumn (NPK-MA). The N2O fluxes, NH4+-N contents, NO3−-N contents, and maize yields were analyzed. The results showed that compared with NPK, NPK-MA increased N2O emissions by 44.4%. Applying pig manure compost in autumn promotes N2O emissions during the freeze–thaw period. However, there was no significant effect of NPK-MS on N2O emissions compared with NPK (p > 0.05). Spring-applied manure compost (NPK-MS) resulted in an 11.9% increase in maize yield compared to NPK. In contrast, autumn-applied manure compost (NPK-MA) did not significantly affect maize yield (p > 0.05). Furthermore, yield-scaled N2O emissions were significantly increased in NPK-MA (p < 0.05). Overall, spring application of pig manure compost is recommended for increasing maize yield without significantly increasing N2O emissions while in Northeast China.