Scientific and reasonable water and fertilizer regimes positively affected crop growth, yield, fruits quality and soil environment improvement. As a liquid quick-acting organic fertilizer to substitute chemical fertilizers, biogas slurry has been widely used in agricultural production. However, the lack of research on the proper comprehensive quality evaluation model and irrigation mode under biogas slurry limits the promotion and large-scale application of biogas slurry in agricultural production. In this study, three biogas slurry (BS) ratio (1:4BS, 1:6BS, 1:8BS; volume ratio of biogas slurry to water), three irrigation levels (W1, W2, W3) and three fertilizer control treatments (CF1, CF2, CF3) were conducted in field experiments. Eleven single indexes from four type qualities (external quality, taste quality, nutrition quality, storage and transportation quality) were adopted to establish the comprehensive evaluation index system of tomato. The principal component analysis, grey correlation analysis, membership function analysis and TOPSIS analysis model (based on the combination of objective entropy method and subjective analytic hierarchy process) were used to estimate the comprehensive quality of tomato fruits. Moreover, the objective combination evaluation mode based on overall diversity was used to evaluate the results obtained from the four independent comprehensive evaluation methods. The aim is to mitigate inconsistencies of multi-attribute evaluation models. The results showed that biogas slurry application was beneficial to the accumulation of aboveground biomass under the same irrigation amount, which can effectively improve the sugar to acid ratio and lycopene content of tomato. T3 (1:4BS, W3) and T1 (1:4BS, W1) obtained the highest yield and water use efficiency (WUE), respectively. The results of Kendall consistency test and Pearson correlation coefficients showed that there were good compatibility and high consistency among the four independent comprehensive evaluation models, and the combined quality evaluation model can be performed directly. As the correlation coefficients between combined evaluation model and each of four independent methods reached 0.965, the combined evaluation model was capable of reducing the differences of four independent comprehensive evaluation model. The combined quality evaluation results showed that T2 (1:4BS, W2) recommended strongly in this study could effectively improve the yield, quality and WUE of tomato.

Soil salinization is a serious threat to the ecological environment and sustainable agricultural development in the arid regions of northwest China. Optimal soil salinization amelioration methods were eagerly explored under different soil salinity levels. Sesbania and hairy vetch are salt-tolerant plants, and green manure improved the saline environment. In this study, two leguminous halophytic crops, sesbania (Sesbania cannabina) and hairy vetch (Vicia villosa), were planted under different salinity levels, combined with three saline soil improvement measures, namely gravel mulching, manure application, and straw returning. No improvement measures and no salinity treatment was set as the control (CK). This study was conducted to analyze the effects of soil salinization improvement measures on the growth and ion uptake of sesbania and hairy vetch as biological measures under different soil salinity levels. Sesbania under manure application absorbed the highest soil Na⁺ (2.71 g kg⁻¹) and Cl⁻ (2.66 g kg⁻¹) amounts at a soil salinity of 3.2 g kg⁻¹, which was 14.7% and 10.95% higher than under gravel mulching and straw returning, respectively. Na⁺ and Cl⁻ absorption of hairy vetch under manure application reached the highest value of 1.39 g kg⁻¹ and 1.38 g kg⁻¹ at a soil salinity of 1.6 g kg⁻¹, which was 24.46% and 22.31% higher than under gravel mulching and straw returning, respectively. Plant height and stem diameter as well as root growth and development of sesbania and hairy vetch were limited at soil salinities greater than 1.6 g kg⁻¹ and 0.8 g kg⁻¹. Overall, sesbania and hairy vetch effectively absorbed both soil Na⁺ and Cl⁻ under manure application, thus regulating soil salinity and reducing soil salinization. However, soil salinity levels greater than 3.2 g kg⁻¹ and 1.6 g kg⁻¹ not only weakened the ionic absorption capacity but also inhibited the growth and development of sesbania and hairy vetch. This study provides evidence that soil salt ion absorption by sesbania and hairy vetch is promoted effectively, ameliorating soil salinity, under manure application as compared to under gravel mulching and straw returning.

To investigate the coupling effects of biochar and nitrogen fertilizer on tomato growth, nitrogen uptake and utilization (NUU), and the soil environment, a pot experiment was conducted using ¹⁵N-tracing technology from March to July 2021 and from September 2021 to January 2022. Three biochar application rates (B0, B1, and B2; 0, 3, and 6 t/hm², respectively) and three nitrogen levels (N1, N2, and N3; 150, 300, and 450 kg/hm², respectively) were set up. The results show that the growth, yield, rate of ¹⁵N uptake, nitrogen derived from soil (Ndfs), total nitrogen (TN), ¹⁵N utilization, and recovery rate of tomatoes were improved under biochar application, but nitrogen derived from fertilizer (Ndff) gradually decreased. A Pearson correlation analysis showed that the ¹⁵N uptake, Ndfs, TN, rhizosphere soil organic matter, soil organic carbon, and TN were significantly positively correlated with the yield and lycopene content of tomatoes. The comprehensive benefit to the tomatoes was evaluated based on combination weighting with the help of the technique for order preference by similarity to ideal solution (TOPSIS). This indicates that the best planting mode was the B2N2 treatment, with a biochar rate of 6 t/hm² and nitrogen levels of 300 kg/hm², under the alternative partial root-zone irrigation.