[Effects of short-term granulated straw incorporation on grain yield and soil respiration in a winter wheat-summer maize cropping system.]

Direct straw return to soils often leads to poor combination between soil and straw, decreases straw decomposition and suppresses crop growth. Those problems hamper crop yield and its stability. Granulated straw with high bulk density and small volume improves the straw quality and the soil-straw combination. It remains unknown how does the practice influence soil carbon emission and grain yield. A micro-field experiment was carried out to investigate the responses of wheat and maize yields, soil respiration and soil carbon use efficiency. There are three treatments: No straw incorporation (CK), conventionally chopped straw incorporation (CCSI), and granulated straw incorporation (GSI). The results showed that the GSI treatment increased grain yield. Compared with the CK and CCSI treatments, the total yield of wheat and maize was significantly increased by 14.0% and 5.8%, respectively. Meanwhile, the GSI treatment promoted soil carbon emission. The average rate of soil respiration and the cumulative carbon emission during growing season were significantly higher than that in the CK treatment. Compared with the CCSI treatment, the rate and the cumulative amount of soil carbon emission during the wheat growing season were significantly elevated by 15.2% and 8.9%, but there was no significant difference during the maize growing season. The GSI treatment decreased the sensitivity of soil respiration to temperature and increased soil carbon use efficiency. Compared with the CK and CCSI treatments, the sensitivity of the GSI treatment was significantly decreased by 22.6% and 10.1%, and the efficiency was increased by 2.3% and 1.9%. Although granulated straw incorporation promoted soil carbon emissions, it had higher soil carbon use efficiency than conventionally chopped straw incorporation due to the higher yield. The application of granulated straw incorporation could serve as a new option of straw return to soil in Huang-Huai-Hai region. Further research was needed to understand the long-term effects of granulated straw incorporation on soil carbon emission.