The large amount of nitrogen application on the North China Plain has caused a serious negative impact on the sustainable development of regional agriculture and ecological environmental protection. Our aim was to explore the effects of nitrogen fertilization rate and groundwater depth on growth attributes, soil-water and soil-fertilizer contents, and the winter wheat yield. Experiments were carried out in micro-lysimeters at groundwater depths of 60, 90, 120, and 150 cm on the basis of 0, 150, 240, and 300 kg/ha nitrogen fertilization rates in the growth season for winter wheat. Results showed that plant height, leaf area index, soil plant analysis development, and yield without nitrogen application increased significantly with increases in groundwater depth. The optimal groundwater depths for growth attributes and yield were 60–120 cm and tended to be shallower with added nitrogen application. Soil moisture was lowered significantly with groundwater depth, adding a nitrogen application reduced soil moisture, and excessive nitrogen input intensified soil drought. Nitrate-N accumulation at the 120–150 cm depths was significantly higher than that at the 60–90 cm depths, and a 300 kg/ha (traditional nitrogen application rate) treatment was 6.7 times greater than that of 150 kg/ha treatment and increased by 74% more than that of the 240 kg/ha treatment at 60–150 cm depth. Compared with the yield of the 300 kg/ha rate, the yield of the 240 kg/ha rate had no significant difference, but the yield increased by 3.90% and 11.09% at the 120 cm and 150 cm depths. The growth attributes and yield of winter wheat were better, and the soil nitrate-N content was lower, when the nitrogen application rate was 240 kg/ha. Therefore, it can be concluded that nitrogen application can be reduced by 20% on the North China Plain.

Facility agriculture in China is facing the challenge of the excessive use of chemical fertilizers (nitrogen fertilizers), which hinder the development of sustainable and environmentally friendly agriculture. Optimizing nitrogen fertilizer allocation is essential to balance agricultural production and environmental concerns. The aim of this study was to determine the optimal organic fertilizer strategy for tomato cultivation under different irrigation methods. An experiment was conducted in a greenhouse, and two irrigation methods, surface irrigation (SI) and drip irrigation (SDI), were used during tomato growth. The fertilization treatments included urea alone (CK); 30%, 40%, and 50% chicken manure mixed with urea (FC1, FC2, FC3); and 50% cow manure and sheep manure mixed with urea (FB3, FS3). The results showed that the irrigation techniques and fertilization had significant effects on ammonia volatilization accumulation, soil mineral nitrogen content, and tomato yield and quality. Compared with the surface irrigation technique with the same amount of fertilizer application, the drip irrigation technique reduced the ammonia volatilization accumulation by a maximum of 76.40%. The SDIFC3 and SDIFB3 ammonia volatilization accumulation was as low as 5.24 (kg·hm⁻²) and 7.61 (kg·hm⁻²); the soil nitrate nitrogen content was reduced, and the tomato yield increased significantly by 17.11%. The SDIFC3 treatment achieved a maximum yield of 13,414 (kg·hm⁻²), increased the tomato vitamin C and soluble sugar contents by 19.13% and 8.97%, and lowered the titratable acid content by as much as 30.51%. Under drip irrigation fertilization conditions, the SDIFC3 treatment showed lower ammonia volatilization accumulation and the highest tomato yield and quality compared to CK and the same proportion of organic fertilizer substitutes with cow and sheep manure. The increase in the proportion of organic fertilizers replacing chemical fertilizers resulted in a gradual decrease in ammonia volatilization accumulation and a gradual increase in the tomato yield and various qualities. The soil mineral N content, on the other hand, was significantly affected by irrigation, fertilizer application, and water–fertilizer interaction effects, with a tendency for the content to increase and then decrease after each fertilizer application. The mineral N content was lower with drip irrigation compared to surface irrigation, especially in the 10–20 cm soil layer than in the 0–10 cm layer. Increasing drip irrigation and organic fertilizer substitution significantly increased the vitamin C and soluble sugar contents in the tomatoes, while decreasing the titratable acid content.

Water scarcity and the uneven distribution of water resources in China have resulted in water shortages for agricultural irrigation in arid and semi-arid areas. Reclaimed water used for agricultural irrigation has become an effective solution in the context of the global water shortage. In order to improve soil productivity and solve the shortage of water resources, we carried out reclaimed water irrigation experiments on polluted soil. Compared with full irrigation treatments, the EC value of reclaimed water under deficit irrigation treatments decreased by 2.89–42.90%, and the content of organic matter increased by 6.31–12.10%. The proportion of Acidobacteria community in soils with different cadmium concentration gradients irrigated with reclaimed water ranged from 13.6% to 30.5%, its relative abundance decreased with the increase of soil cadmium concentration. In particular, the relative abundance of Pseudomonas pathogens in deficit irrigation treatments was lower than that of the full irrigation treatments. RDA analysis showed that the environmental factors that played a leading role in the change of microbial community structure were organic matter and pH. Furthermore, the metabolic function potential of the rhizosphere soil bacterial community in deficit irrigation treatments was higher than that of full irrigation treatments with reclaimed water. This study proved that reclaimed water irrigation for cadmium contaminated soil did not aggravate the pollution level and promoted the soil ecological environment with better microbial community diversity.

As the world economy and society have developed quickly, the amount of farmland soil pollution has become alarming, which has seriously threatened global food security. It is necessary to take effective measures on the moderately contaminated soil to produce high-quality food and to protect food security worldwide by effective use of land resources. Our experimental design was to study the changes in soil physicochemical properties and tomato yield and quality indicators by irrigating tomatoes on cadmium-contaminated soil with two different water qualities (reclaimed water irrigation: RW; tap water irrigation: TW) through drip irrigation devices. Tomato quality indicators were determined using plant physiological assays, as well as vitamin C (VC), total acidity (TA), protein content (PC), and soluble sugar content (SS). We tested five different types of cadmium-contaminated soils (less than 0.60 mg/kg, 0.60–1.20 mg/kg, 1.20–1.80 mg/kg, 1.80–2.40 mg/kg, 2.40–3.00 mg/kg) against RW and TW, and performed high-throughput sequencing of the soils to obtain environmental results for soil microbial diversity. The results reveal that compared with the TW condition, soil nutritional status was increased with the irrigated RW. The yield of the tomatoes increased by 52.03–94.03% than TW. The results of the study showed significant and highly significant relationships between tomato quality indicators (TA, SS, yield) and soil physical and chemical properties indicators (p < 0.01, 0.05). For instance, the RW increased the SOM by 6.54–12.13%, the TP by 0.48–24.73%, the yield of the tomatoes by 52.03–94.03% than TW, while the cadmium content did not show significant differences (p < 0.05), and the cadmium content did not increase the soil’s pollution level. Compared with TW treatment, RW treatment alleviated the inhibition of soil microbial diversity by cadmium and RW also increased its soil microbial diversity. The relative abundance of Proteobacteria, Gemmatimonadetes, and Bacteroidetes in the RW condition were higher than in the TW condition at different cadmium concentrations. In conclusion, RW improved the overall quality conditions of soil and the diversity of microbial communities, and did not aggravate the pollution degree of cadmium-contaminated soil, and affected the yield of tomatoes positively. RW can be an effective irrigation technique to reduce the use of clean water.

Effects of Bacillus subtilis and Saccharomyces cerevisiae inoculation on soil bacterial community and rice yield under combined irrigation with reclaimed and fresh water

Introduction: Agricultural water scarcity and cadmium (Cd) contamination threaten global food security. Reclaimed water (RW) and partial root-zone alternate irrigation (PRA) offer possible solutions, but their synergistic effects on Cd-contaminated soils remain unclear. Objective: This study evaluated the impacts of PRA with RW on Cd-polluted tomato-growing soils. Methods: A pot experiment was conducted with 5 Cd levels (0.30–2.74 mg/kg, 5 replicates each). Soil properties, enzyme activities, Cd fractions, and 16S rRNA microbiome were analyzed. Results: PRA with RW increased rhizosphere pH by 0.42 units (p < 0.01), decreased EC by 18.7% (p < 0.05), and available Cd by 12.3% (p < 0.05). Catalase activity rose by 27.47% (p < 0.05), while sucrase and urease decreased by 32.1% and 28.5% (p < 0.01). Beneficial Actinobacteria (+8.26%) and Proteobacteria (+4.64%) were enriched, and Bacillus was reduced by 11.8%. Flavisolibacter (r = 0.802, p < 0.001) and Nocardioides (r = 0.572, p < 0.001) were key genera. Conclusions: PRA with RW reduces Cd bioavailability and ecological risks, providing a sustainable strategy for mildly/moderately polluted farmland soil.