Response of soil respiration and carbon budget to irrigation quantity/quality and biochar addition in a mulched maize field under drip irrigation

Abstract BACKGROUND Biochar addition strongly alters net carbon (C) balance in agroecosystems. However, the effects of biochar addition on net C balance of maize field under various irrigation water quantities and qualities remains unclear. Thus, a field experiment combining two irrigation levels of full (W1) and deficit irrigation (W2 = 1/2 W1), two water salinity levels of fresh (S0, 0.71 g L −1 ) and brackish water (S1, 4 g L −1 ), and two biochar addition rates of 0 t ha −1 (B0) and 60 t ha −1 (B1) was conducted to investigate soil carbon dioxide (CO 2 ) emissions, maize C sequestration and C budget. RESULTS Compared with W1, W2 reduced average cumulative CO 2 emissions by 6.5% and 19.9% for 2020 and 2021, respectively. The average cumulative CO 2 emissions under W1S1 treatments were 5.4% and 22.3% lower than W1S0 for 2020 and 2021, respectively, whereas W2S0 and W2S1 had similar cumulative CO 2 emissions in both years. Biochar addition significantly increased cumulative CO 2 emissions by 17.8–23.5% for all water and salt treatments in 2020, and reduced average cumulative CO 2 emissions by 11.9% for W1 but enhanced it by 8.0% for W2 in 2021. Except for W2S1, biochar addition effectively increased total maize C sequestration by 6.9–14.8% for the other three treatments through ameliorating water and salt stress over the 2 years. Compared with W1S0, W1S1 did not affect net C sequestration, but W2 treatments significantly decreased it. Biochar addition increased net C sequestration by 39.47–43.65 t C ha −1 for four water and salt treatments for the 2 years. CONCLUSION These findings demonstrate that biochar addition is an effective strategy to increase both crop C sequestration and soil C storage under suitable water‐saving irrigation methods in arid regions with limited freshwater resources. © 2023 Society of Chemical Industry.