In agroecosystems, effective straw return modes are one of the key practices for increasing soil fertility and carbon (C) availability. Although they improve soil quality, there is currently little information available regarding the influence of distinct straw return modes with respect to potential soil organic carbon (SOC) sequestration. In this study, we established a five-year (2015–2019) field experiment in Mollisols of Northeast China, which included four straw return modes, plow tillage with straw return as the control (PTS), rotary tillage with straw return (RTS), rotary tillage with straw strip return (RSS), and plow tillage with straw strip return (PSS), to investigate the impact on soil physicochemical properties, aggregates, and C sequestration. The results reveal that RSS effectively improved the soil physicochemical properties. Such responses increased the contents of SOC, fulvic acid carbon (FAC), and humin carbon (HMC) in all soil layers (0–30 cm). The proportion of macroaggregates was higher in RSS, whereas the proportion of silt/clay was the lowest at depths of 0–20 cm; consequently, the mean weight diameter (MWD) and geometric mean diameter (GMD) of RSS were higher at depths of 0–20 cm due to the improved physical soil structure. In the 0–10 cm and 20–30 cm layers, the highest humic acid carbon (HAC) concentrations associated with all aggregate sizes were found for RSS, in contrast to 10–20 cm, which had increased HMC. Structural equation modeling (SEM) revealed that C transformation was mainly mediated through silt/clay-associated FAC, HMC, and SOC, ultimately determining HAC (81%) and HMC (85%) as the primary humus fractions for SOC sequestration. Therefore, this study shows that RSS is the suitable straw return mode for effectively improving soil quality, aggregate stability, and C sequestration in Mollisols of Northeast China.

Straw is widely incorporated into conservation agriculture around the world. However, its effects on greenhouse gas emissions (GHGs) and nitrogen dynamics under soils formed by the long-term application of different amounts of nitrogen (N) fertilizer are still unclear. An incubation experiment was conducted on soils collected from a field study after 6 years of contrasting N fertilization of 0 (low N), 187 (medium N), and 337 kg N ha⁻¹ (high N), with and without maize straw. Straw amendment significantly stimulated both nitrous oxide (N₂O) and carbon dioxide (CO₂) fluxes (p < 0.05), and increased cumulative emissions by 0.8 and 19.0 times on average compared to those without straw incorporation. Medium-N soil observably weakened N₂O emissions (23.8 μg kg⁻¹) compared to high-N soil (162.7 μg kg⁻¹), and increased CO₂ emissions (1.9 g kg⁻¹) compared to low-N soils (2.3 g kg⁻¹) with straw amendment. Soil NH₄⁺-N and NO₃⁻-N invariably increased with rising soil N level, whereas straw promoted the turnover of mineral N by enhancing soil N fixation capacity. From the first day until the end of incubation, NH₄⁺-N decreased by 79.0% and 24.7%, while NO₃⁻-N showed a decrease of 58.8% or an increase of 75.2%, depending on whether straw was amended or not, respectively. Moreover, partial least squares path modeling and random forest mean predictor importance were used to find that straw affected GHGs by altering the N turnover capacity. Straw amendment increased GHGs and diminished the risk of losing mineral N by enhancing its turnover. Combining straw with medium-N soil could mitigate the greenhouse effect and improve the N and carbon (C) balance in farming systems compared to low- and high-N soils. This is recommended as a farmland management strategy in Northeast China.

Background and aims Straw incorporation was widely accepted in the world for conservation agriculture, whereas the effects on greenhouse gases emissions (GHGs) and nitrogen dynamics under soils formed by long-term contrasting nitrogen (N) fertilizer are still unclear.Methodology An incubation experiment was conducted with or without maize straw using soils collected from fields study after 6-year contrasting N fertilization of 0 (low N), 187 (medium N) and 337 kg N ha^− 1 (high N).Results Straw amendment significantly stimulated both N₂O and CO₂ fluxes, and increased cumulative emission by 0.82 and 18.98 times than without straw incorporation on average, respectively. Medium N soil observably weakened N₂O emission (23.76 µg kg^− 1) than high N soil (162.71 µg kg^− 1) and attenuated CO₂ emission (1.85 g kg^− 1) than Low N soil (2.30 g kg^− 1) soils with straw amendment. Soil NH₄⁺-N and NO₃⁻-N dynamics kept the increasing trend with rising soil N, whereas straw accelerated the decrease of NH₄⁺-N from 24.72–78.98%, and reversed the tendency of NO₃⁻-N from enrichment (+ 75.19%) to scarcity (-58.83%) compared to straw removal due to higher soil N fixation capacity. Moreover, partial least squares path modeling and random forest mean predictor importance disentangled straw affected GHGs by altering nitrogen turnover capacity.Conclusion Straw amendment promoted GHGs and enhanced mineral N turnover and diminished the risk of losses. Combing straw with medium N soil could mitigate greenhouse effect and improvement N and C balance in farming system compared to the low and high N soils.

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.