Effects of rice straw mulching on N2O emissions and maize productivity in a rain-fed upland.

In the hilly areas of southern China, uplands and paddies are located adjacent to each other. Using rice straw as mulch for upland soil may improve crop production and partially replace chemical fertilizers, which may mitigate N2O emissions. A field experiment was conducted to investigate the potential of rice straw mulching for mitigating N2O emissions and increasing crop production. The treatments included no mulching (CK), 5000 kg ha-1 of straw mulching (SM5), and 10,000 kg ha-1 of straw mulching (SM10). Moreover, all the treatments received equivalent amounts of nitrogen, phosphorus, and potassium from chemical fertilizers plus rice straw. Relative to CK, cumulative N2O emissions decreased by 23.1 and 33.5% with SM5 and SM10, respectively. Significant positive correlations were observed between N2O fluxes and soil water-filled pore space (WPFS) (r 2 = 0.495, P < 0.05) and between seasonal cumulative N2O fluxes and the chemical N fertilization rate (r 2 = 0.814, P < 0.05). These findings indicate that soil WPFS was the key environmental factor in N2O emissions and that the substitution of chemical nitrogen fertilizer with rice straw was the main driver of N2O mitigation. Relative to CK, the maize yield increased by 16.5 and 29.6% with SM5 and SM10, respectively, which can be attributed primarily to the increases in soil moisture. The chemical fertilizer input could be decreased and N2O emissions could be mitigated through straw mulching, while achieving improved crop yield. This management strategy has great potential, and this study provides an important reference for low-carbon agriculture.