Introduction: There are serious problems in agricultural production, such as low nitrogen utilization rate and nitrate leaching. This study examined how different fertilization practices affect the yield, quality, and soil nitrate leaching of greenhouse tomatoes in the cold regions. The goal was to provide technical support for simple, high-quality, and efficient greenhouse vegetable production in these areas. Methods: Under integrated water-fertilization conditions in the cold regions, six fertilization treatments were applied: No nitrogen fertilizer, Conventional farmer practice (360 kg ha ^-1 N), Optimized nitrogen application (240 kg ha ^-1 N), Slow-release urea A mixed with conventional urea at 7:3 (240 kg ha ^-1 N), Slow-release urea B mixed with conventional urea at 7:3 (240 kg ha ^-1 N), Conventional urea mixed with modified slow-release polymer material (240 kg ha ^-1 N). Results: The results showed that optimized nitrogen treatments improved plant height and SPAD values, which helped increase yield. Among them, conventional urea mixed with modified slow-release polymer material had the highest yield. Optimized fertilization treatments also improved quality. Agronomic efficiency and partial factor productivity under optimized nitrogen treatments were 59.08%-231.95% higher than under conventional farmer practice. These treatments also reduced nitrate accumulation in the 60-100 cm soil layer. Using a multi-objective evaluation model based on fuzzy mathematics membership function, conventional urea mixed with modified slow-release polymer material was identified as the best option. Discussion: In summary, under integrated water-fertilization conditions, applying conventional urea mixed with modified slow-release polymer material can maintain tomato yield and quality while reducing soil nitrate leaching. This method meets the demands of modern agriculture and environmental protection.

This study evaluated the effects of water–fertilizer coupling on the water and fertilizer use efficiency, yield, and quality of fresh common beans (Phaseolus vulgaris L.) in high-latitude and high-altitude regions. For field water-saving, in 2022, six treatments were established, with irrigation rates of 100% FC (W1), 90% FC (W2), 80% FC (W3), 70% FC (W4), 60% FC (W5), and 50% FC (W6). Based on the experiment in 2022, a two-factor experiment (irrigation and fertilizer application rate) was implemented in 2023, and three fertilizer (N−P₂O₅−K₂O) gradients were established: F1 (260−192−255 kg/ha), F2 (195−144−192 kg/ha), and F3 (131−97−127 kg/ha). Based on 2022, three irrigation rates were established at percentages of FC: W7 (100% FC), W8 (80% FC), and W9 (60% FC). Experiments in both years revealed a quadratic relationship (parabola equation) between yield and the rates of both irrigation and fertilization. Excessive fertilization did not consistently enhance yield, and reduced fertilizer application resulted in higher fertilizer partial factor productivity (PFP). Both years of experiments indicated that maintaining soil moisture at 80%~90% field capacity (FC) significantly improved fresh pod yield and water use efficiency (WUE) compared to other treatments. Under the same fertilizer level, reduced irrigation increased key fresh pod quality indicators, such as single-pod weight and soluble sugar content. In contrast, across varying fertilizer rates, these same indicators showed a positive correlation with the amount of fertilizer applied. Vitamin C (VC), soluble protein (SP), soluble solids content (SSC), and nitrate content (NC) reached their highest levels under high fertilizer treatment (N−P₂O₅−K₂O: 260−192−255 kg/ha). Based on the differential comprehensive evaluation models, the study concluded that maintaining soil moisture at 80%~90% FC and applying fertilizer between N−P₂O₅−K₂O: 195−144−192 kg/ha and N−P₂O₅−K₂O: 260−192−255 kg/ha was the optimal strategy. This approach can alleviate the water scarcity pressure in high-latitude and high-altitude regions, and facilitate the selection of common bean management practices that maintain yield while improving quality and PFP, thereby offering theoretical and practical guidance for adapting water–fertilizer regimes to local climatic conditions.