The indiscriminate use of nitrogen fertiliser (NF) is a obstruction to improve soil quality and crop yields. However, the effect of biochar and NF on soil microbial ecosystem (SME) and crop yields is unknown. A five-year field experiment in China aimed to evaluate the effects of biochar and nitrogen fertiliser (NF) combination on soil structure, C-to-N ratio (CNR), microbial biomass, and spring maize yield. Biochar and NF were applied at different rates, and the combined application resulted in a soil solid–liquid–gas ratio closer to the ideal value. The use of biochar alone and in combination with NF significantly increased soil's C, N, and CNR. A moderate application of biochar and NF resulted in favourable biological and chemical properties of the soil. The application of biochar and NF at moderate levels led to an increase in SME, with the B8N150 producing the highest yield. The highest yield of B8N150 represents a 24.25% increase compared to the unfertilized control and a 9.04% increase compared to B0N150. Moderate use of biochar and NF could be beneficial in areas with similar climatic conditions.

Biochar application can alter soil properties and enhance soil quality. However, the effects of the regulatory mechanisms underlying nitrogen fertilizer application on soil physicochemical properties and microbial characteristics remain unclear. We conducted a three-year maize field experiment to investigate the effects of four biochar application rates (0, 8, 16, and 24 t/ha) and three nitrogen fertilizer rates (0, 150, and 300 kg/ha) on soil physicochemical properties, enzyme activities, microbial community structure, and maize yield. In the 0–20 cm soil layer, the combined application of biochar and nitrogen fertilizer significantly increased soil porosity (SP) and soil water content (SWC), reduced soil bulk density (SBD), and increased soil organic carbon (SOC) and total nitrogen (TN) levels. Additionally, β-D-cellobiohydrolase and leucine aminopeptidase activities were enhanced, along with nitrogen acquisition potential. The relative abundance of Proteobacteria was highest at a biochar application rate of 16 t/ha. The combined 16 t/ha biochar and 150 kg/ha nitrogen treatment exhibited the highest maize yield. Maize yield was positively correlated with SP, SWC, SOC, and TN. Consequently, the combined application of 16 t/ha biochar and 150 kg/ha nitrogen improved soil physicochemical properties, enhanced soil enzyme activities, regulated key soil microbial taxa, and increased maize yield.

Drip irrigation is widely used to conserve water and maintain crop production in water‐limited regions. However, how contrasting drip irrigation systems shape soil water‐salt movement, water and nitrogen (N) use, and maize productivity in semi‐arid environments remains poorly understood. Here, we conducted a two‐year field experiment (2019–2020) with a randomized complete block design to compare shallow buried drip irrigation (SBDI) and mulched drip irrigation (MDI). Relative to MDI, SBDI increased grain yield, dry matter accumulation, and N uptake by 5.86%, 3.11%, and 9.58%, respectively, contributin to greater water and N use efficiency. Soil salinity dynamics were closely coupled with soil water movement, representing a remarkable accumulation in the 0–20 cm soil layer under SBDI compared to MDI, owing to higher evapotranspiration. Although both irrigation systems resulted in soil salt accumulation, SBDI was more conducive for chloride ion elution. Partial least squares path modeling, Random forest, and Mantel tests suggested that water N utilization and salt dynamics were highly related to maize productivity. Our findings enrich the theoretical framework for preventing secondary soil salinization by inhibiting soil resalinization via water regulation or interlayer installation. In the future, the integration of SBDI with desalination measures may be a crucial strategy for enabling sustainable high‐yield maize production in semi‐arid regions.

Indiscriminate use of nitrogen fertiliser (NF) is a barrier to improving soil quality and crop yields. However, the effect of the combined use of biochar and NF on soil microbial ecosystem (SME) and crop yields is unknown. In the western Liaohe Plain of China, we conducted a five-year field experiment to assess the effects of the combination of biochar and NF on soil structure, C-to-N ratio (CNR), microbial biomass, and spring maize yield. Biochar and NF were applied at 0, 8, 16, and 24 t/ha and 0, 150, and 300 kg/ha, respectively. Compared to their individual use, combination of biochar and NF resulted in a solid–liquid–gas ratio closer to the ideal value. Biochar alone and in combination with NF significantly increased the C, N, and CNR. Moderate use of biochar and NF resulted in the best biological and chemical properties of the soil. A comprehensive evaluation of soil and maize revealed that SME was enhanced by applying biochar and NF at moderate levels (8 t/ha and 150 kg/ha, respectively). The highest yield represents a 24.25% increase compared to the control. Moderate use of biochar and NF has potential as a valuable strategy in regions with similar climate.