Biochar application reduced carbon footprint of maize production in the saline−alkali soils

The amendment of biochar to cropland has been recommended as a potential strategy to mitigate climate change and increase soil fertility by enhancing carbon (C) storage. Quantifying the environmental benefits and resulting carbon footprint (CF) of integrating biochar and fertilizer treatments is paramount in facing intensified human activities of agricultural land expanding under climate change, especially in fragile inland catchments for saline-alkalis soils. A three−year field experiment was conducted with maize in the Tarim River Basin to monitor greenhouse gas (GHG) emissions, maize yield, soil organic carbon (SOC), and CF from 2020 to 2022. This study involved seven treatments that varied in nitrogen (N) fertilizer, irrigation, and biochar applications: (i) 0N0W (0 kg N ha−1, 0 mm, 0 t ha−1 biochar), (ii) LNLW (100 kg N ha−1, 140 mm, 0 t ha−1 biochar), (iii) LNLWB (100 kg N ha−1, 140 mm,10 t ha−1 biochar), (iv) MNMW (200 kg N ha−1, 220 mm, 0 t ha−1 biochar), (v) MNMWB (200 kg N ha−1, 220 mm, 10 t ha−1 biochar), (vi) HNHW (300 kg N ha−1, 320 mm, 0 t ha−1 biochar) (conventional treatment), and (vii) HNHWB (300 kg N ha−1, 320 mm, 10 t ha−1 biochar). The results showed that biochar amendment (LNLWB, MNMWB, HNHWB) reduced CO2 emissions by (7%, 8%, 7%), accumulative emission of CH4 and N2O (AE) (19%, 15%, 15%), greenhouse gas intensity (GHGI) (32%, 24%, 22%) and CF (77%, 61%, 56%), and increased SOC sequestration (47%, 46%, 46%), maize yield (19%, 12%, 12%) compared to no biochar (LNLW, MNMW, HNHW) CO2 emission (3355, 4141, 4619 kg CO2−C ha−1), AE (148, 221, 469 kg CO2−eq ha−1), GHGI (16.3, 21.2, 40.6 kg CO2−eq t−1 yield), CF (1373, 1990, 2784 kg CO2−C ha−1), SOC (14.2, 15.1, 15.6 Mg C ha−1), maize yield (9.1, 10.6, 11.5 t ha−1). Furthermore, compared to HNHW, LNLWB reduced 32% CO2, 74% N2O, 89% CF, and increased 39% SOC. Overall, the biochar application (10 t ha−1) with reduced N (100 kg N ha−1) input in the Tarim River Basin, is a win−win strategy for reducing CF, enhancing C sequestration, and supporting stable food production, and it is a low–carbon agricultural strategy for farmland in saline−alkali soils.