The yield, quality, and water–fertilizer use efficiency of crops are important parameters for assessing rational water and fertilizer management. For an optimal water and fertilizer system with respect to the nutrient solution irrigation of greenhouse tomatoes using cultivation substrates, a two-year greenhouse cultivation experiment was conducted from 2022 to 2023. Three drip fertigation treatments (T1, T2, and T3) were implemented in the experiment, where nutrient solutions were supplied when the substrate’s water content reached 60%, 70%, and 80%. The frequency of nutrient solution applications is based on weighing coconut coir strips in the morning and evening at 7:00 to determine the daily water consumption of plants. Nutrient solutions were supplied when the substrate’s water content reached the lower limit, and the upper limit for nutrient supply was set at 100% of the substrate water content. The nutrient solution application was carried out multiple times throughout the day, avoiding the midday heat. The nutrient solution formula used was the soilless tomato cultivation formula from South China Agricultural University. The results show that plant height and the leaf area index rapidly increased in the early and middle stages, and later growth tended to stabilize; the daily transpiration of tomatoes increased with an increase in nutrient solution supply, and it was the greatest in the T3 treatment. Between the amount of nutrient solution application and the number of years, the yield increased with the increase of the amount of nutrient solution, showing T3 > T2 > T1. Although the average yield of the T2 treatment was slightly lower than that of the T3 treatment by 3.65%, the average irrigation water use efficiency, water use efficiency, and partial fertilizer productivity of the T2 treatment were significantly higher than those of the T3 treatment by 29.10%, 19.99%, and 28.89%, respectively (p < 0.05). Additionally, soluble solid, vitamin C, and soluble sugar contents and the sugar–acid ratio of tomatoes in the T2 treatment were greater than those in the other two treatments (p < 0.05). Using the TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) method, it was concluded that the nutrient solution application rate of 70% can significantly increase water and fertilizer use efficiency and markedly improve the nutritional and flavor quality of the fruit without a significant reduction in yield. This finding provides significant guidance for the high-yield, high-quality, and efficient production of coconut coir-based cultivated tomatoes in greenhouses.

Drought stress can impact the physiological and biochemical properties of crops. However, selenium (Se) can effectively alleviate the abiotic stress experienced by plants. This study aims to investigate how applying selenium to tomato leaves affects their antioxidant system and photosynthetic traits when subjected to drought conditions. The experiment used four different foliar selenium concentrations and three different irrigation levels. The investigation scrutinized the effects of foliar spraying employing different selenium concentrations on the antioxidant system, osmotic adjustment substances, photosynthetic performance, and growth indices of tomatoes under drought stress. The findings indicated that drought stress led to cellular oxidative damage, significantly elevating peroxide, MDA, proline, and soluble sugar content (p < 0.001). Under severe drought stress, malondialdehyde (MDA) and proline levels increased by 21.2% and 110.0% respectively, compared to well-watered conditions. Concurrently, the net photosynthetic rate exhibited a reduction of 26.0% and dry matter accumulation decreased by 35.5%. However, after spraying with a low concentration of selenium, selenium reduced oxidative damage and malondialdehyde content by reducing the content of peroxide in leaves, restoring photosynthesis, and promoting the normal growth of tomato. Compared to the control group, spraying with 2.5 mg·L⁻¹ selenium resulted in a 21.5% reduction in MDA content, a 111.8% increase in net photosynthetic rate, and a 29.0% increase in dry matter accumulation. When subjected to drought stress conditions, foliar spraying of low concentrations of selenium (2.5 mg·L⁻¹) can effectively reduce oxidative damage caused by drought stress and alleviate growth constraints in tomatoes. In addition, treatments with high selenium concentrations exhibited specific toxic effects. These findings offer valuable insights into the mechanisms governing selenium-induced drought tolerance in tomatoes, thus advancing our comprehension of standard tomato production practices.

To address the scientific challenges of low water–fertilizer use efficiency and the difficulty in achieving the synergistic improvement of the yield and quality in solar greenhouse cucumber production on the North China Plain, this study investigated the effects of varying water and nitrogen supplies on cucumber growth, yields, water–nitrogen use efficiency, and quality. The aim was to establish optimized water and nitrogen management strategies for high-yield, high-quality, and resource-efficient cultivation. A two-factor completely randomized design was implemented, with three irrigation levels (W1: $1.0E_{p-20}$, W2: $0.75E_{p-20}$, and W3: $0.5E_{p-20}$) based on cumulative pan evaporation and four nitrogen application amounts (N1: 432 kg·ha⁻¹, N2: 360 kg·ha⁻¹, N3: 288 kg·ha⁻¹, N4: 216 kg·ha⁻¹). Cucumber growth indicators were observed during the growing season, and the water and nitrogen application rates were scientifically optimized. The results showed that a full water and nitrogen supply enhanced the leaf area index, dry weight accumulation, and yield. Moderate water and nitrogen savings had a minimal impact on plant growth and production while significantly improving the water and fertilizer use efficiency. Using principal component analysis to comprehensively evaluate the cucumber quality, it was found that the irrigation amount had a significant impact on quality, with the quality improving as the irrigation amount decreased. By employing a regression formula and spatial analysis methods, this study optimized the water and nitrogen application rates with the goals of maximizing the cucumber yield, water–nitrogen efficiency, and quality. For spring cucumbers, the recommended combination is an irrigation amount of 225~240 mm and a nitrogen application amount of 350~380 kg·ha⁻¹. For autumn cucumbers, the recommended combination is an irrigation amount of 105~120 mm and a nitrogen application amount of 375~400 kg·ha⁻¹. This research provides theoretical and technical support for high-yield, high-quality, and efficient irrigation and nitrogen management in solar greenhouses in the North China Plain.

Soil salinity and water deficit are important challenges for sustainable agricultural development in arid and semi-arid regions. While soil salinity and water deficits may result in lower crop yields, they may improve crop quality. The quantitative relationship between water–salt stress, crop yield, and quality is key to achieving stable yield and enhanced quality through the coordinated regulation of soil water and salt. The interaction between soil salinity and deficit irrigation on tomato quality needs to be further understood, and the model simulating the response of tomato quality to deficit irrigation under simulated soil salinity needs to be further optimized. In this study, a two-year experiment was conducted in northwest China consisting of combinations of three soil salinity levels (0 g, 3 g, and 5 g mixed salt added to 1000 g air-dried soil, respectively) and four water regimes relative to the field capacity (θ_f) (W0, W1, W2, and W3 refer to 95% θ_f, 80% θ_f, 70% θ_f, and 60% θ_f as the upper limit of soil water content, respectively). The responses of plant stem water potential (φ), fruit osmotic potential (φ_π), fruit Na⁺ content, fruit fresh weight, fruit water content, total soluble solids (TSS), lycopene (Ly), soluble sugars content (SSC), and color index (CI) to the degree of water deficit and the stage of water deficit were analyzed under soil salinity. The results show that both soil salinity and water deficit significantly reduced φ, but there is no significant interaction. TSS, SSC, and CI are all significantly affected by soil salinity, degree of water deficit, and stage of water deficit, and there is a significant interaction between the degree of water deficit and soil salinity. Fruit fresh weight, TSS, Ly, SSC, and CI are all strongly correlated with φ, and the straight lines of regression of each index with φ are significantly affected by soil salinity content. Soil salinity significantly increased the Na⁺ content in the fruit, and water deficit significantly enhanced the effect of soil salinity on the Na⁺ content of tomato fruit. A functional model to simulate fruit quality was developed based on the response of fruit quality parameters to φ and the effect of fruit Na⁺ accumulation under the compound effect of soil salinity and water deficit. The validation results of the model show that this function model effectively simulates tomato fruit quality under the combined effects of soil salinity and water deficit, providing a theoretical basis for soil water–salt management in arid and semi-arid regions.

Calibration of crop model parameters using optimization algorithms can substantially improve model performance, particularly under different environmental scenarios. Here, we take greenhouse drip-irrigated tomato as an example. Two temperature treatments (high temperature, TH: 35 °C ≤ T_max ≤ 40 °C; non-high temperature, TD: T_max ≤ 35 °C) and two water treatments (well watered, WH: 100%E_pan; water deficit, WD: 60%E_pan, where E_pan is the pan evaporation coefficient) were combined and implemented in 2024 and 2025. Canopy cover, yield, aboveground biomass, and water consumption of tomatoes were measured, and then a global sensitivity analysis was conducted using the extended Fourier amplitude sensitivity test (EFAST). Thereafter, in order to evaluate the performance of AquaCrop-OSPy under different combinations of temperature and water conditions, the whale optimization algorithm (WOA) was coupled with the AquaCrop-OSPy model, and an automatic parameter optimization framework was developed using the aforementioned measured indicators as objective functions. The results showed that CC_x, Senescence_CD, CGC_CD, WP, HI₀, and K_cb were highly sensitive parameters of the AquaCrop-OSPy model across different temperature and water treatments. Compared with the traditional trial and error (TAE) method, WOA demonstrated superior global optimization capability and significantly improved model performance. Validation indicated that the root mean square error (RMSE) was ≤4.52% for canopy cover, ≤0.67 t/hm² for yield, and ≤0.98 t/hm² for aboveground biomass. Notably, even after WOA optimization, water consumption simulation under combined high temperature and water deficit conditions still showed some deviation, which was attributed to limitations in soil water simulation and the oversimplification of model mechanisms under combined stress. Nevertheless, the model remained reliable for estimating canopy cover, yield, and biomass, while ET simulation under combined stress should be interpreted with caution. Therefore, future improvements of AquaCrop-OSPy should focus on addressing the effects of soil water and refining the inhibitory feedback of physiological stress to better adapt the model to the combined conditions of high temperature and water deficit.

High temperature is a primary meteorological hazard restricting crop yield and quality, particularly in semi-automatic greenhouses. However, the accuracy of crop models under controlled high-temperature conditions in greenhouses has rarely been examined. To address this, our study evaluated the AquaCrop (7.1) and DSSAT (4.8.2) models for greenhouse-grown tomato under high-temperature conditions. Field experiments were conducted over two consecutive years (2024 and 2025) with two temperature treatments (TH: daily maximum temperature > 35 °C; TD: daily maximum temperature < 35 °C) and two irrigation levels (WH: 100%E_pan; WD: 60%E_pan, where E_pan is cumulative pan evaporation). Key indicators were continuously measured, including canopy cover, soil water content, above-ground biomass, yield, and water consumption. Additionally, the XGBoost algorithm was introduced to estimate reference crop evapotranspiration across different treatment combinations, facilitating a multi-scenario analysis. The results indicated that under both TD and TH conditions, the AquaCrop model accurately simulated canopy cover (RMSE ≤ 6.84%, NRMSE ≤ 12.27%, EF ≥ 0.92), yield (PE ≤ 12.20%), above-ground biomass (PE ≤ 2.34%), and water consumption (PE ≤ 10.33%) across different irrigation levels. However, its performance in simulating soil water content declined markedly under the TH treatment, with EF becoming negative in some cases (−1.66 ≤ EF ≤ 0.43), indicating that the model was largely ineffective for SWC under these conditions. The DSSAT model exhibited lower simulation accuracy under the TH treatment compared to the TD treatment, and its overall performance was slightly inferior to that of the AquaCrop model (RMSE ≤ 15.79 mm, NRMSE ≤ 14.54%, −1.68 ≤ EF ≤ 0.46). Scenario analysis of 20 temperature and irrigation combinations, integrating XGBoost-derived ET₀ into the AquaCrop model, revealed that maximizing greenhouse tomato yield requires a combination strategy of 1.1E_pan and 34 °C, whereas optimizing water use efficiency is best achieved under 0.9E_pan and 32 °C. These findings provide a theoretical basis and technical support for the application of crop models and the development of environmental regulation strategies in greenhouse cultivation under high-temperature conditions.