Agricultural wastes have the potential to enhance the utilization rate and production efficiency in saline-alkali land. In this study, humic acid was incorporated into a substrate module composed of agricultural wastes, including wine lees and straw. A series of experiments was conducted to investigate the effects of various substrates on soil salinity in saline-alkali environments. The "Jinpeng 8 Type B" tomato served as the test sample. Three types of saline-alkali soils were selected: mild S1 (Ec = 1.15 mS/cm, pH value is 8.63), moderate S2 (Ec = 3.67 mS/cm, pH value is 9.13), and heavy S3 (Ec = 6.39 mS/cm, pH value is 9.69). Six groups of humic acid additions were established: T0 (0), T1 (2‰), T2 (4‰), T3 (6‰), T4 (8‰), and T5 (10‰), with the treatment lacking humic acid serving as the control group. The analytic hierarchy process (AHP) and entropy weight methods were employed to assign subjective and objective weights to each indicator. The final weights for each indicator related to tomato cultivation were derived from this assignment. A TOPSIS multi-objective comprehensive evaluation model was constructed, incorporating 16 indicators across three categories: tomato growth physiological indicators, yield, and fruit quality. This model facilitated the determination of optimal substrate allocation for the different types of saline-alkali soils. The results indicated a trend of increasing and then decreasing soil salinity across different types of saline-alkaline soils during the tomato growth stages, from seedling to flowering, fruit enlargement, and maturity. The salt content exhibited a similar trend of increasing and then decreasing with increasing soil layer depth. At the same depth, soil salinity decreased with the addition of humic acid to the substrate. The average salt contents of each soil layer for mild, moderate, and heavy saline-alkali soils treated with 10‰ humic acid were reduced by 60.57%, 13.14%, and 8.31%, respectively, compared to the control group. Notably, the addition of humic acid was most effective in improving mild saline-alkali soil conditions. The humic acid treatment significantly enhanced plant height, stem diameter, soil and plant analyzer development (SPAD), root characteristics, yield, and quality of tomatoes (P<0.05). The parameters for tomato plant height, stem diameter, SPAD value, and root characteristics exhibited a trend of increasing and then decreasing with higher amounts of humic acid added. An optimal combination was identified for evaluating tomato plant height, stem diameter, SPAD value, root characteristics, yield, and quality. In comparison to the absence of humic acid, the addition of 4‰, 6‰, and 8‰ humic acid in mild, moderate, and heavy saline-alkali soils, respectively, resulted in corresponding increases in root quality of 51.17%, 49.60%, and 56.98%, indicating a well-developed root system. The comprehensive indexes for tomatoes were 0.9030, 0.8934 and 0.8304 in mild, moderate, and heavy saline-alkali soils with 4‰, 6‰, and 8‰ humic acid, respectively. These findings provide a theoretical basis for the efficient utilization of agricultural waste and the scientific management of high-quality fruit and vegetable production in saline-alkali land.

This study aimed to enhance the utilization of agricultural waste and identify the most suitable agricultural waste materials for tomato cultivation. It utilized a locally modified substrate labeled as CK, along with five different groups of agricultural waste materials, designated as T1 (organic fertilizer: loessial soil: straw in a ratio of 4:5:1), T2 (organic fertilizer: loessial soil: straw: grains in a ratio of 3:5:1:1), T3 (organic fertilizer: loessial soil: straw: grains in a ratio of 2:5:1:2), T4 (organic fertilizer:loessial soil:straw:grains in a ratio of 1:5:1:3), and T5 ( loessial soil:straw:grains in a ratio of 5:1:4), the AquaCrop model was employed to validate soil water content and tomato growth and yield under these treatments. Furthermore, a multi-objective genetic algorithm was employed to determine the optimal agricultural waste materials that would ensure maximum tomato yield, water use efficiency (WUE), partial factor productivity of fertilizer (PFP) and sugar-acid ratio. The results indicated that the AquaCrop model reasonably simulated volumetric soil water content, tomato canopy cover, and biomass, with root mean square error (RMSE) ranges of 20.0-69.4 mm, 15.2%-25.1%, and 1.093-3.469 t/hm², respectively. The CK group exhibited an R-squared (R²) value of 0.63 for volumetric soil water contents, while the ratio scenarios showed R² values exceeding 0.80. The multi-objective genetic optimization algorithm identified T5 as the optimal ratio scenario, resulting in maximum tomato yield, WUE, PFP, and quality. This study offers a theoretical foundation for the efficient utilization of agricultural wastes and the production of high-quality fruits and vegetables.

Substrate cultivation has been characterized by the high yield and quality of tomatoes in recent years. Furthermore, biochar can be recognized as the soil conditioner to serve as the ideal additive in the substrate, due to the abundant porosity and the large specific surface area. This study aims to clarify the effects of irrigation and fertilizer coupling on the yield and quality of tomatoes cultivated in a biochar substrate. The biochar was incorporated into the substrate mixture that included agricultural wastes, such as distiller's grains and straw. A greenhouse experiment was conducted to investigate the effects of varying irrigation and fertilizer regimes on the leaf area index (LAI), soil and plant analyzer development (SPAD), plant nutrient uptake, N/K ratio, C/N ratio, yield, and quality of tomato cultivated in biochar substrate. The experiment consisted of two irrigation levels: I₁ (100% ET_c, where ET_c referred to crop evapotranspiration) and I₂ (80% ET_c); two fertilization rates (N-P₂O₅-K₂O): F₁ (240-180-200 kg/hm²) and F₂ (180-135-150 kg/hm²); and four amounts of biochar application: B₀ (0), B₁ (1%), B₃ (3%), and B₅ (5%). Furthermore, a structural equation model (SEM) was utilized to explore the driving factors of water-fertilizer coupling on the yield and quality of tomatoes cultivated in biochar substrate. Additionally, an entropy weight-TOPSIS model of multi-objective evaluation was also constructed with the targeting yield, quality, and their key driving factors. The optimal scheme was identified for the coupling of water and fertilizer with the biochar substrate. The results indicated that the biochar substrate had significant effects on LAI, SPAD value, nutrient uptake, yield, and quality of tomatoes (P < 0.05). Under the same conditions of irrigation and fertilization, the biochar substrate improved the potassium absorption and carbon assimilation of the whole plant, yield, and vitamin C content in the tomato plants while simultaneously reducing nitrate content. Furthermore, under the same fertilization rate, the yield decreased with the decrease of irrigation amount, and the soluble solids content, vitamin C content, and soluble sugar content increased with the decrease of irrigation amount. Compared with the I₁ treatment, the I₂ treatment resulted in an average decrease in yield by 13%, and an average increase in soluble solids content, vitamin C content, and soluble sugar content by 17%, 8%, and 11%, respectively. The SEM revealed that the carbon assimilation of the whole plant was the primary influencing factor on the yield, indicating a significant positive correlation (λ=0.96, P<0.001). The N/K ratio emerged as the principal regulatory factor for both nitrate content and the sugar-acid ratio, indicating a significant negative correlation with the sugar-acid ratio (λ=-0.66, P<0.01) and a significant positive correlation with nitrate content (λ=0.53, P<0.001). The SPAD value shared an indirect promoting effect on the yield and quality. According to the entropy weight-TOPSIS model of a multi-objective comprehensive evaluation, the I₁F₂B₃ treatment had the highest comprehensive ranking with a relative closeness degree of 0.76. Therefore, I₁F₂B₃ treatment can be the optimal coupling strategy of water and fertilizer and biochar substrate to synergistically improve yield and quality. This research can provide a theoretical basis to improve the utilization rate of agricultural waste and the effective management of irrigation, fertilizer, and biochar in the cultivation of high-quality vegetables.