Irrigation using saline water is extensively used in areas of agricultural production where freshwater is scarce. However, saline water irrigation adversely impacts soil’s physicochemical characteristics and crop productivity. In this study, we established irrigation water with five salinity levels (EC_iw, 1.3, 3.4, 7.1, 10.6, 14.1 dS·m⁻¹) to investigate how these salinity levels influenced grain yields as well as soil salinity, alkalinity, sodicity, and aggregate stability in the 0~20 cm soil layer of a wheat and maize rotation field (in 2022–2023). Tukey’s test, entropy-weighted TOPSIS, and the least squares method were used to analyze the significance analysis, comprehensively evaluate the soil aggregate stability and soil index comprehensive score (SICS), and achieve linear fitting, respectively. The results showed that when EC_iw > 3.4 dS·m⁻¹, there was a significant increase in the soil salinity, pH, and sodium adsorption ratio. When EC_iw > 7.1 dS·m⁻¹, a significant reduction in soil aggregate stability was observed. When EC_iw ≤ 3.4 dS·m⁻¹, there was no significant reduction in the grain yields of wheat and maize. Furthermore, the annual grain yields of wheat and maize decreased by 5% and 10%, respectively, resulting in a change in EC_iw values from 2.98 to 4.24 dS·m⁻¹, based on the linear regression analysis of SICS and EC_iw, as well as the annual grain yields and SICS. Under uniform irrigation conditions, the soil salinity, alkalinity, and sodicity were lower, and soil aggregate indexes were more stable at the maturity stage of maize.

Water scarcity is a key limitation to winter wheat production in the North China Plain, and it is essential to explore the optimal timing of spring irrigation to optimize N and Si uptake as well as to safeguard yields. The aim of this study was to systematically study the effect mechanism of nitrogen and silicon absorption of winter wheat on yield under spring irrigation and to provide a scientific basis for optimizing irrigation strategy during the growth period of winter wheat. In this experiment, the winter wheat ‘Heng 4399’ was used. Five irrigation periods, i.e., 0 d (CK), 5 d (AJ5), 10 d (AJ10), 15 d (AJ15), and 20 d (AJ20) after the jointing stage, were set up to evaluate the nitrogen (N) and silicon (Si) absorption and grain yield (GY). The results showed that delayed irrigation for 5–10 days at the jointing stage had increased the GY. With the delay of irrigation time, the N/Si content of the entire plant at the maturity period increased first and then decreased; among that, the maximum N contents appeared in AJ15 and AJ5 in 2015 and 2020, respectively, while the Si concentrations appeared in AJ5 and AJ10 in sequence. Compared with AJ15 and AJ20, the N accumulation of vegetative organs in AJ5 increased by 3.05~23.13% at the flowering stage, 14.12~40.12% after the flowering stage, and a 1.76~6.45% increase in the N distribution rate at maturity stage. A correlation analysis revealed that the GY was significantly and positively correlated with the N/Si accumulation at the anthesis and N translocation after the anthesis stage. In conclusion, under limited irrigation conditions, delaying watering for 5 to 10 days at the jointing stage can improve the nitrogen and silicon absorption and nutrient status of wheat plants and increase wheat yield.

Subsurface drip irrigation is an advanced technique that significantly enhances agricultural water efficiency and conserves irrigation resources. The Heilonggang region is highly representative of the maize–wheat rotation system in China. This region was selected for conducting operations and maintenance experiments on subsurface drip irrigation systems. The primary objective of this study was to determine the most suitable type of drip tape for application in the North China Plain and to identify specific maintenance measures necessary to ensure the long-term functionality of subsurface drip irrigation systems. The experiment was conducted in Jing County, Hengshui City. Anti-blocking drip tape (Netafim Co., Ltd. Beijing, China) with automatic functionality was evenly laid in the test area. The experimental area was divided into six rotational irrigation groups. The key parameter examined in this single-factor experiment was the drip tape wall thickness, with values of 0.2, 0.225, 0.25, 0.28, 0.31, and 0.38 mm. Drip tape treatments were randomly sampled in rotational irrigation groups, and there were three repeat plots in each treatment. Each replicate plot contained ten drip irrigation belts spaced 60 cm apart, with an interval of more than 2 m between adjacent plots. The subsurface drip irrigation system was installed in October 2023. Prior to irrigation, drip tape troubleshooting was conducted and recorded manually on 12 March 2024 (wheat regreening stage) and 29 June 2024 (maize-sowing stage). The experimental findings indicated that the primary factor influencing the stability of the irrigation system was the wall thickness of the drip tapes, while other system components operated efficiently. A significant correlation was observed between the wall thickness of the drip tape and the number of water leakage points (p < 0.05), with an absolute correlation coefficient exceeding 0.9. The number of leakage points in drip tapes with wall thicknesses of 0.2–0.28 mm (267 instances) was significantly higher than those with wall thicknesses of 0.31–0.38 mm (29 instances), primarily due to damage caused by mole crickets and wireworms. Following the injection of 40% phoxim, 2.5% lambda-cyhalothrin, and 70% imidacloprid insecticides (at a cost of 16.7 USD·ha⁻¹) into the subsurface drip irrigation system, the insect pests were nearly eradicated within one month. A cumulative cost evaluation over a 6–10-year period recommended the use of drip tapes with a wall thickness of 0.31 mm and the application of insecticides every 1–2 months to maintain optimal system performance in this region. These measures can effectively support the stable operation of this irrigation technique at a relatively low cost.

The inconsistent efficacy of biochar in mitigating agricultural greenhouse gas emissions remains a major barrier to its widespread adoption and the realization of its environmental benefits. This study aimed to develop a stable and efficient mitigation strategy by optimizing biochar physicochemical properties through urea-N activation (corn stover: urea mass ratios of 5:1 and 15:1). Five treatments were established: CK (control), GC (fertilization), GB (fertilization + raw biochar), GAB5 (fertilization + low-N activated biochar), and GAB15 (fertilization + high-N activated biochar). Mechanisms were elucidated by monitoring soil profile (0–20 cm) gas concentrations and surface fluxes, combined with a comprehensive analysis of soil physicochemical properties, enzyme activities, and microbial biomass. Results demonstrated that activated biochar, particularly GAB15, significantly reduced cumulative CO₂ (9.4%, p < 0.05) and N₂O (45.2%, p < 0.05) emissions and their concentrations in the 0–10 cm layer. This superior efficacy was linked to profound improvements in key soil properties: GAB15 significantly enhanced soil cation exchange capacity (CEC, increased by 17.3%, p < 0.05), NH₄⁺-N content (increased by 88.2%, p < 0.05), Mean Weight Diameter (MWD, increased by 13.0%), the content of water-stable aggregates > 0.25 mm (R_>0.25mm, increased by 57.3%) (p < 0.05), dissolved organic carbon (DOC), and the MBC (microbial biomass carbon)/MBN (soil microbial biomass nitrogen) ratio. Redundancy analysis (RDA) and structural equation modeling (SEM) revealed core mechanisms: CO₂ mitigation primarily stemmed from the physical protection of organic carbon within macroaggregates and a negative priming effect induced by an elevated MBC/MBN ratio; N₂O mitigation was attributed to weakened nitrogen mineralization due to enhanced aggregate stability and reduced substrate (inorganic N) availability for nitrification/denitrification via strong adsorption at the biochar–soil interface. This study confirms that urea-activated biochar produced at a 15:1 corn stover-to-urea mass ratio (GAB15) effectively overcomes the inconsistent efficacy of conventional biochar by targeted physicochemical optimization, offering a promising and technically feasible approach for mitigating agricultural greenhouse gas emissions.

Diversified cropping systems exhibited enhanced resource utilization efficiency, yet the nitrogen (N) allocation mechanisms and utilization patterns in economic-grain rotation systems remain poorly understood. This study investigated the cross-seasonal N allocation dynamics and photosynthetic responses to N reduction in a garlic–maize rotation system through a three-season field experiment with graded N treatments (garlic, 300 and 240 kg N ha ⁻¹ ; maize, 220, 175, and 130 kg N ha ⁻¹ ). N reduction increased soil water-filled pore space (WFPS) by 5.2%–8.7% during maize seasons but decreased it in garlic seasons. It also reduced topsoil (0–20 cm) NO ₃ ⁻ –N accumulation by >15% compared to deeper layers. Leaf physiological parameters—including leaf area index (LAI), SPAD values, and net photosynthetic rates—declined by 18%–32% under N reduction, with garlic demonstrating higher sensitivity. Residual N from preceding garlic crops stabilized maize LAI (± 6.5%), indicating compensatory inter-season adjustments. Critical thresholds were identified: maize achieved optimized grain nitrogen partitioning (65% to 72%) and a 22% improvement in nitrogen use efficiency (NUE) with a reduction of 45 kg N ha ⁻¹ without a significant yield penalty (less than 5%). Conversely, garlic experienced a 23% increase in stem nitrogen translocation when nitrogen was reduced by 60 kg N ha ⁻¹ , which resulted in a 34% decrease in bulb allocation. Annual N reduction (8.65%–28.85%) enhanced maize agronomic efficiency (+40%) but reduced garlic yields (4.2%–27.5%) and partial factor productivity (−18%). These results reveal contrasting, crop-specific N allocation strategies and support the development of demand-driven N management to balance productivity and economic outcomes in multi-cropping systems.

Saline water irrigation is a potential strategy to address agricultural water scarcity, but its effects on soil respiration and carbon balance are not well understood. To clarify these effects and promote the safe utilization of saline water resources, this study investigated five irrigation water salinity levels EC_iw: 1.3, 3.4, 7.1, 10.6, and 14.1 dS·m⁻¹ (i.e., 1, 2, 4, 6, 8 PSU; 1000, 2000, 4000, 6000, 8000 mg·L⁻¹) in a winter wheat–summer maize rotation during 2024–2025. The results indicated that saline water irrigation caused salt accumulation during the wheat season, whereas salt leaching occurred during the maize season. When EC_iw ≤ 3.4 dS·m⁻¹, no notable decreases were observed in dry matter accumulation, water productivity, and carbon emission efficiency for both crops. In contrast, when EC_iw > 3.4 dS·m⁻¹, the crop yields and net carbon input of the crop rotation system were suppressed to a considerable extent. Furthermore, under saline water irrigation, the average soil respiration rate decreased by 4.1–25.2% during the wheat growing season, while that for maize decreased by 7.4–30.7%. Soil respiration in wheat was negatively correlated with soil salinity and pH, and positively correlated with soil moisture (p < 0.01). In maize, soil respiration was negatively correlated with salinity (p < 0.01), and positively correlated with soil moisture (p < 0.05) and temperature (p < 0.01). The entropy-weighted TOPSIS model identified 3.4 dS·m⁻¹ as the appropriate irrigation salinity threshold for maintaining yield and carbon sink function in this rotation system.