Responses of greenhouse gas emissions to different straw management methods with the same amount of carbon input in cotton field

• Comparison between straw-biochar and straw under an equal C input. • CO 2 from soil heterotrophic respiration was included in GHG emissions. • Straw return increased CO 2 and CH 4 but suppressed N 2 O emissions. • Straw-biochar suppressed emissions of CO 2 , CH 4 and N 2 O simultaneously. • Straw-biochar reduced GHGI by reducing GWP and enhancing cotton yield. Recycling crop straw to cropland can improve soil fertility, increase crop yield, and enhance soil carbon (C) sequestration, but also increase the risk of soil greenhouse gas (GHG) emissions. However, the differences in GHG emissions among different straw management methods are not well understood. Here, we investigated the responses of GHG emissions and their driving factors to the application of straw (S, 5.0 t ha −1 ), straw plus microbial inoculant (SI, 5.0 t ha −1 ), straw mulching (SM, 5.0 t ha −1 ), straw-biochar (SB, 3.5 t ha −1 ), and no straw or straw-biochar (CK) based on an equal amount of C input in a cotton field in Yancheng city, Jiangsu province, China from 2017 to 2018. Our results showed that the carbon dioxide (CO 2 ) emissions from soil heterotrophic respiration were decreased markedly under SB, but increased markedly under SI and S. The response of soil methane (CH 4 ) emissions to all treatments was similar to the CO 2 emissions. Soil nitrous oxide (N 2 O) emissions were consistently decreased under SB, SI, S and SM, ranking as CK > SM > S>SI > SB. Compared with CK, SI and S significantly increased the global warming potential (GWP), whereas SB significantly decreased GWP by 17.9 %–19.8 %. Lint yield of cotton was highest in SB, followed by SI, S and SM, and lowest in CK. Consequently, SI, S and SM had no significant effects on the greenhouse gas intensity (GHGI), but SB significantly decreased GHGI by 28.4 %–35.7 %. In conclusion, straw-biochar application is an effective option for mitigating global warming and sustaining crop productivity.