Controlled-release urea (CRU) fertilizers are widely used in agricultural production to reduce conventional nitrogen (N) fertilization-induced agricultural greenhouse gas emissions (GHGs) and improve N use efficiency (NUE). However, the long-term effects of different CRU fertilizers on GHGs and crop yields in vegetable fields remain relatively unexplored. This study investigated the variations in GHG emissions at four growth stages of lettuce in the spring and autumn seasons based on a five-year field experiment in the North China Plain. Four treatments were setup: CK (without N application), U (conventional urea—N application), ON (20% reduction in urea—N application), CRU (20% reduction in polyurethane-coated urea without topdressing), and DCRU (20% reduction in polyurethane-coated urea containing dicyandiamide [DCD] without topdressing). The results show that N application treatments significantly increased the GHG emissions and the lettuce yield and net yield, and DCRU exhibited the lowest N₂O and CO₂ emissions, the highest lettuce yield and net yield, and the highest lettuce N content of the N application treatments. When compared to U, the N₂O emission peak under CRU and DCRU treatments was notably decreased and delayed, and their average N₂O emission fluxes were significantly reduced by 10.20–20.72% and 17.51–29.35%, respectively, leading to a significant reduction in mean cumulative N₂O emissions during the 2017–2021 period. When compared to U, the CO₂ fluxes of DCRU significantly decreased by 8.0–16.54% in the seedling period, and mean cumulative CO₂ emission decreased by 9.28%. Moreover, compared to U, the global warming potential (GWP) and greenhouse gas intensity (GHGI) of the DCRU treatment was significantly alleviated by 9.02–17.13% and 16.68–20.36%, respectively. Compared to U, the N content of lettuce under DCRU was significantly increased by 6.48–17.25%, and the lettuce net yield was also significantly increased by 5.41–7.71%. These observations indicated that the simple and efficient N management strategy to strike a balance between enhancing lettuce yields and reduce GHG emissions in open-field lettuce fields could be obtained by applying controlled-release urea containing DCD without topdressing.

Vegetable-oil-based polyurethane has become a promising sustainable candidate for controlled-release fertilizer based on green chemistry. The purpose of this study was to prepare a series of coatings from selective feedstocks including five vegetable oils with a high saturation degree, mono-unsaturation degree, or poly-unsaturation degree, considering that vegetable oil fatty acids played a key role in the synthesis of polyol and polyurethane. The effect of the type and proportion of fatty acids on the physicochemical properties, microstructure, and macro-properties of vegetable-oil-derived polyols and their resulting coatings was characterized and discussed. The position and number of the hydroxy groups were determined by the type and proportion of fatty acid, and polyol from linseed oil with a high poly-unsaturation degree and three carbon–carbon double bonds had a high hydroxyl value and functionality, whereas polyol from palm oil with a high saturation degree possessed the lowest hydroxyl value and functionality. The resultant coating from linseed-oil-based polyol had a good cross-linking density, and the nitrogen release longevity of coated urea was 56 days at a coating percentage of 3%, and its nitrogen use efficiency was increased by 27.15% compared with conventional urea. Although the palm-oil-based coating had good hydrophobicity, its coated urea was not ideal. Overall, this study has enriched theories of bio-based polyurethane coatings for controlled-release fertilizers; using vegetable oil with a poly-unsaturation degree, it is easy to obtain an excellent coating for controlled-release fertilizer, and this will help provide economic and environmental benefits.

The coordination and balance between agricultural development (AD) and agricultural carbon emissions (ACE) is one of the most important ways to boost the high-quality development of agriculture in the Beijing-Tianjin-Hebei region. Taking 13 prefecture-level cities in the Beijing-Tianjin-Hebei region as the research object, this study uses the comprehensive evaluation method and Tapio decoupling model to analyze the decoupling effect between the AD level and the Agricultural Carbon emissions intensity (ACEI) from 2000 to 2020, based on the assessment of AD status and the calculation of Agricultural Carbon emissions quantities (ACEQ) and ACEI. It found that: (1) From 2000 to 2020, the AD in the Beijing-Tianjin-Hebei region generally showcased a gradual increase trend, and demonstrated a basic feature that AD in the northern areas was higher than that in the southern ones. (2) From 2000 to 2020, the ACEQ in the Beijing-Tianjin-Hebei region showed a trend of first increasing and then decreasing, with a spatial distribution feature that the ACEQ in the southern cities was higher than that in the northern ones. Regarding the source of ACE, the livestock and poultry farming took the highest proportion. ACEI was decreasing year by year, higher in the southern areas than in the northern ones. (3) The main types of decoupling in the Beijing-Tianjin-Hebei region were strong decoupling, recession decoupling, strong negative decoupling, weak negative decoupling, recession coupling, and expansion negative coupling. The decoupling relationship between AD and ACEI were in dynamic change, but the change trend of the decoupling relationship was optimistic. The results of this study deliver certain deployable practice value for improving the sustainability of regional agricultural green development and ecological environmental protection.

To reduce crop-related water consumption and enhance agricultural water resource efficiency in the Beijing–Tianjin–Hebei region, this study employed the AquaCrop model to simulate crop yield and irrigation water requirements and calculated the water scarcity footprint (WSF). The results were as follows: (1) The AquaCrop model exhibited strong applicability, with R², RMSE (Root Mean Square Error), EF (Nash–Sutcliffe model efficiency coefficient) and d values of 0.9611, 6.6%, 0.91, and 0.98 (winter wheat), and 0.9571, 5.5%, 0.95, and 0.99 (summer maize) for canopy cover simulation. Similarly, aboveground biomass simulation yielded values of 0.9661, 0.8 t/ha, 0.93, and 0.98 (winter wheat), and 0.9087, 1.3 t/ha, 0.90, and 0.98 (summer maize). Winter wheat soil moisture content simulation showed an R² of 0.9706, RMSE of 3.7 mm, EF of 0.93, and d of 0.98. (2) The AquaCrop model simulated the winter wheat and summer maize yields and irrigation water requirements for the years 2009, 2014, and 2019, validating the scalability and spatial visualization capabilities of GeoSim in extending AquaCrop simulations. (3) Integrating the water footprint and the water resources system, this study assessed the WSFs of winter wheat and summer maize. From 2009 to 2019, winter wheat production in the region increased by 25.08%, and summer maize production increased by 37.39%. The WSF of winter wheat decreased, whereas the WSF of summer maize increased. It is recommended to reduce crop cultivation areas in regions such as Daming County, Ningjin County, and Dingzhou City while further improving irrigation water efficiency, which would facilitate the sustainable utilization of water resources in the area.

Semi-arid Chernozem farmland in Northeast China faces the dual challenges of water scarcity and excessive nitrogen (N) fertilisation, yet quantitative understanding of coupled water–N use efficiency and environmental trade-offs under climatic variability remains limited. Using the WHCNS (Water, Heat, Carbon and Nitrogen Simulator) model calibrated and validated against field data (2022–2023) from Qiqihar, we quantified crop yield, water use efficiency (WUE), System-Level Nitrogen Conversion Efficiency (SLNCE) and N losses under five management regimes encompassing conventional fertilisation, straw mulching and organic manure substitution. Long-term climate adaptability was evaluated using precipitation scenarios from 2001 to 2023. Straw mulching reduced evapotranspiration by 12.2% and increased WUE to 2.09 kg·m⁻³. Combined chemical and organic fertiliser application (T223) achieved the highest yield (9745.9 kg·ha⁻¹) and WUE (2.14 kg·m⁻³), whereas a 30% reduction in chemical fertiliser with straw return (T323) reduced yield and SLNCE, indicating insufficient N supply. Organic substitution achieved the highest SLNCE (35.9 kg·kg⁻¹), exceeding the straw-only treatment by 29.1%. Nitrate leaching below 1 m was negligible, whereas gaseous N losses were the dominant loss pathway and increased with rainfall. SLNCE responded nonlinearly to precipitation, peaking at 420–451 mm; extreme drought years constrained yield through nitrogen limitation, whereas wet years increased gaseous N losses while maintaining relatively high yields. These results show that organic substitution can simultaneously enhance WUE and SLNCE, providing a climate-adaptive strategy for sustainable water–N management in semi-arid Chernozem soils.