Prior nitrogen fertilization regulates CH4 emissions from rice cultivation by increasing soil carbon storage in a rapeseed-rice rotation

Abstract

Given the high nitrogen (N) fertilizer input in crop production systems, the residual effects of the N fertilizer have been increasing continuously. However, its influence on methane (CH4) emissions remains unknown. A field experiment was carried out to investigate the response of CH4 emissions from rice cultivation to the preceding rapeseed N fertilization in a rapeseed-rice rotation system. The N fertilizer was applied during the rapeseed season at N loading rates of 0 and 150 kg N ha−1. During the rice season, the original treatment during the rapeseed season was split into with and without N application subtreatments, totaling in four treatments (N0–0, N0–150, N150–150, and N150–0). Results showed that CH4 emissions were not influenced by N fertilization during the rapeseed season. However, that N fertilization remarkably enhanced CH4 emissions at the seedling stage of the rice-growing season in the fertilized or nonfertilized treatments. This result was caused by the increased soil carbon budget and soil ammonium (NH4+-N) content. The residual effects of N fertilizer contributed 20.3% (N150–0) and 17.5% (N150–150) to the cumulative CH4 emissions of the whole rice-growing season. CH4 emissions at the tillering stage were significantly (p < 0.05) affected by the current rice N fertilization, and N0–150 and N150–150 treatments were approximately 1.9- and 2.4-fold greater than N0–0 and N150–0 treatments, respectively. Moreover, the N fertilizer applied during the rapeseed and the rice seasons increased the above- and belowground biomass of rice plants. Overall, the role that residual N plays cannot be ignored in studying the regulatory mechanism of CH4 emissions from rice fields under upland-rice rotation system.