Excessive chemical fertilizers degrade soil and increase greenhouse gas (GHG) emissions. Organic substitution of nitrogen fertilizers is recognized as a sustainable agricultural-management practice, yet its dual role in carbon sequestration and emissions renders the net GHG balance (NGHGB) uncertain. To assess the GHG mitigation potential of organic substitution strategies, this study analyzed GHG fluxes, soil organic carbon (SOC) dynamics, indirect GHG emissions, and Net Primary Productivity (NPP) based on a long-term field positioning experiment initiated in 2016. Six fertilizer regimes were systematically compared: no fertilizer control (CK); only phosphorus and potassium fertilizer (PK); total chemical fertilizer (NPK); 1/3 chemical N substituted with sheep manure (OF1); dual substitution protocol with 1/6 chemical N substituted by sheep manure and 1/6 substituted by straw-derived N (OF2); complete chemical N substitution with sheep manure (OF3). The results showed that OF1 and OF2 maintained crop yields similar to those under NPK, whereas OF3 reduced yield by over 10%; relative to NPK, OF1, OF2, and OF3 significantly increased SOC sequestration rates by 50.70–149.20%, reduced CH₄ uptake by 7.9–70.63%, increased CO₂ emissions by 1.4–23.9%, decreased N₂O fluxes by 3.6–56.2%, and mitigated indirect GHG emissions from farm inputs by 24.02–63.95%. The NGHGB was highest under OF1, 9.44–23.99% greater than under NPK. These findings demonstrate that partial organic substitution increased carbon sequestration, maintained crop yields, whereas high substitution rates increase the risk of carbon emissions. The study results indicate that substituting 1/3 of chemical nitrogen with sheep manure in maize cropping systems represents an effective fertilizer management approach to simultaneously balance productivity and ecological sustainability.

Improving plant water use efficiency is a key strategy for the utilization of regional limited water resources as well as the sustainable development of agriculture industry. To investigate the effects of different land use types on plant water use efficiency and their mechanisms, a randomized block experiment was designed in the agro-pastoral ecotone of northern China during 2020–2021. The differences in dry matter accumulation, evapotranspiration, soil physical and chemical properties, soil water storage and water use efficiency and their relationships among cropland, natural grassland and artificial grassland were studied. The results show that: In 2020, the dry matter accumulation and water use efficiency of cropland were significantly higher than those of artificial and natural grassland. In 2021, dry matter accumulation and water use efficiency of artificial grassland increased significantly from 364.79 g·m⁻² and 24.92 kg·ha⁻¹·mm⁻¹ to 1037.14 g·m⁻² and 50.82 kg·ha⁻¹·mm⁻¹, respectively, which were significantly higher than cropland and natural grassland. The evapotranspiration of three land use types showed an increasing trend in two years. The main reason affecting the difference of water use efficiency was that land use type affected soil moisture and soil nutrients, and then changed the dry matter accumulation and evapotranspiration of plants. During the study period, the water use efficiency of artificial grassland was higher in years with less precipitation. Therefore, expanding the planted area of artificial grassland may be one of the effective ways to promote the full utilization of regional water resources.

Tillage practices can disrupt soil surface, creating loose, erodible soil layers. This significantly impacts soil organic carbon (SOC) fractions, including microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), readily oxidizable organic carbon (ROC), and heavy fraction organic carbon (HFOC). SOC fractions may depend on soil aggregate size. However, the variation patterns of SOC fractions under different soil aggregate sizes and tillage practices remain unclear. The objectives of this study were to assess the impact of tillage practices on SOC fractions (MBC, DOC, POC, ROC, and HFOC) within soil aggregates and to quantify the relationship between aggregate size and these SOC fractions. Seven treatment combinations were selected: two conventional tillage practices of rotary tillage (RTS) and plow-tillage (PTS) with 100% harvest maize stover mulching, and five conservation tillage practices of subsoiling+100% mulching (STS), no-tillage+30% (NTS1) and 100% (NTS2) mulching, and no-tillage & ridging+30% (NTSR1) and 60% (NTSR2) mulching. Results showed that tillage practices significantly impacted SOC fractions and maize yield (P < 0.05). Specifically, conservation tillage outperformed conventional tillage in enhancing SOC and its labile labile organic carbon (LOC, including MBC, DOC, POC, ROC) by retaining crop residues, increasing carbon inputs, and reducing mechanical disturbance. Mineral-associated organic carbon (MAOC) and heavy fraction organic carbon (HFOC) are classified as stable SOC fractions, and conservation tillage also promoted the accumulation of stable SOC. NTS2 was optimal for SOC accumulation in the 0-20 cm soil layer. STS promoted root carbon input in the 20-40 cm soil layer. Maize yield was the highest under STS and the lowest under RTS. Particularly, ROC (2 mm, 2-0.25 mm) remarkably affected maize yield. Overall, this study demonstrates that the STS treatment can provide an optimal pathway for achieving both high SOC sequestration and maize yield. Future research should further elucidate the coupling mechanism between microbial functional redundancy and carbon turnover dynamics under long-term tillage practices to provide theoretical support for precision agricultural management.

Long-term crop rotation can improve soil function and crop performance, but it remains unclear whether rotation history can simultaneously alleviate drought-induced oxidative injury in spring wheat leaves and roots. To address this gap, we used a long-term field rotation experiment established in 2016 in the western foothills of the Greater Khingan Mountains. Four cropping systems were selected: spring wheat–potato rotation (R1), spring wheat–potato–rape rotation (R2), spring wheat–rape rotation (R3), and continuous spring wheat cropping (C1). In 2022, wheat occurred naturally in all rotation sequences, and all plots were planted with the same spring wheat cultivar (‘Longmai 36’) to enable comparison among different rotation histories. Drought stress was imposed from late jointing, and at anthesis, ROS-related levels, malondialdehyde (MDA), glutathione (GSH), and proline (Pro), as well as the activities of superoxide dismutase (SOD) and peroxidase (POD), were determined in the flag leaves and roots of spring wheat under normal-water (NC) and drought-stress (HC) conditions. Under drought stress, rotation significantly increased yield (R1 and R2 by 73.3% and 77.7% vs. C1, respectively, partly reflecting the low C1 baseline associated with continuous cropping) and reduced drought-induced accumulation of ROS-related levels and MDA, along with excessive antioxidant and osmotic responses. R1 better protected leaves, while R2 optimized root osmotic regulation. Two-way ANOVA revealed significant drought × rotation interactions for most leaf traits (p < 0.01) but not for root ROS-related levels, SOD, or POD, indicating organ-specific regulation. R1 and R2 show strong drought resilience potential, warranting multi-year, multi-site validation.