Effect of Carbon Content in Wheat Straw Biochar on N2O and CO2 Emissions and Pakchoi Productivity Under Different Soil Moisture Conditions

Agricultural soils are a primary source of greenhouse gas (GHG) emissions. Biochar is commonly used as a soil amendment to prevent climate change by reducing GHG production, increasing soil carbon storage, improving soil moisture retention, and enhancing crop productivity. However, the impact of biochar’s carbon content under subsurface drip irrigation (SDI) has not been well studied. Here, we investigated the effect of different carbon (C) contents in wheat biochar under different SDI depths on soil nitrous oxide (N2O), carbon dioxide (CO2), soil moisture distribution, and Pakchoi productivity. A pot experiment was conducted using three SDI depths, emitters buried at 0.05, 0.10, and 0.15 m below the soil’s surface, and three levels of C content named zero biochar (CK), 50% C (low (L)), and 95% C (high (H)) in greenhouse cultivation. The findings showed biochar significantly decreased N2O and CO2 emissions. Compared to CK, the L and H treatments decreased N2O by (18.20, 28.14%), (16.65, 17.51%), and 11.05, 18.65%) under SDI5, SDI10, and SDI15, respectively. Similarly, the L and H treatments decreased CO2 by (8.05, 31.46%), (6.96, 28.88%), and (2.97, 7.89%) under SDI5, SDI10, and SDI15, respectively. Compared to CK, L and H increased soil moisture content. All plant growth parameters and yield traits were enhanced under SDI5. In summary, biochar addition significantly decreased soil N2O and CO2 emissions compared to CK, and increased growth performance and yield, and maintained soil moisture content. The H treatment significantly reduced N2O and CO2 emissions, increased plant growth and yield, and maintained soil moisture content compared to the L treatment. Soil moisture was reduced vertically and horizontally with increased radial distance from the emitter.