Waste/reclaimed irrigation water has been promoted due to water shortages in arid and semi-arid areas. However, this process may be one of the sources of phthalate esters (PAEs) in agricultural soils, and the potential risks of PAEs for soil ecosystems and human health have attracted considerable attention. A two-year (from October 2014 to October 2016) field experiment was conducted to assess the contamination risk of PAEs from reclaimed irrigation water in winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) fields on the North China Plain. Three types of irrigation water quality were arranged for each variety, including reclaimed water, groundwater, and a mixture of reclaimed water and groundwater (1:1, v/v). The results indicate that the concentrations of the 6 PAEs in topsoil ranged from 2.79 to 5.34 mg/kg at the time of crop harvest. There was no significant effect of reclaimed irrigation water on the concentrations of PAEs in the soil. Di-n-butyl phthalate (DnBP) and di (2-ethylhexyl) phthalate (DEHP) were the most abundant contaminants in all soil samples, accounting for 43.2%~68.7% and 27.1%~48.6%, respectively, of the 6 PAEs. The levels of dimethyl phthalate (DMP) and DnBP in all soil samples exceeded the allowable soil concentrations, but the levels were far below the recommended soil cleanup objectives. The grain yields of winter wheat and summer maize ranged from 4.35 to 7.1 t/ha and 1.03 to 6.46 t/ha, respectively. There were no significant effects of reclaimed water on the growth characteristics and grain yield of winter wheat (p > 0.05); however, the effect of reclaimed irrigation water on summer maize was influenced by climate. The concentrations of the 6 PAEs in wheat grain and maize grain ranged from 1.03 to 4.05 mg/kg and from 0.37 to 3.29 mg/kg, respectively. For the same variety, there was no significant difference in the concentrations of the 6 PAEs in cereal grains among different treatments (p > 0.05). DEHP and DnBP were the most abundant components in most crop samples, accounting for 31.6%~77.9% and 21.1%~64.7%, respectively, of the 6 PAEs. The concentrations of the PAEs, DnBP and DEHP in cereal grains were lower than those in the reference doses. The BCFs of the 6 PAEs and of each PAE in cereal grains were 0.43~1.25 and 0.33~35.75, respectively. The BCFs of butyl benzyl phthalate (BBP) were the highest (1.41~35.75), followed by DMP and DEHP. There were almost no significant differences in the BCFs of each PAE among the three treatments. The total carcinogenic risks of PAEs were 2.82 × 10⁻⁵ for adults and 1.81 × 10⁻⁵ for children. The total non-carcinogenic risks of PAEs were 3.37 × 10⁻¹ for adults and 7.98 × 10⁻¹ for children. DHEP was the dominant contributor to both risks, and the intake of cereals was the main exposure pathway for the two risks. In conclusion, there were no significant effects of reclaimed irrigation water on the concentrations of PAEs in soil and cereal grains compared with groundwater irrigation, and the human health risks were within the acceptable range. Long-term studies are needed to evaluate the long-term effects of reclaimed irrigation water on the contamination risk posed by PAEs.

Straw returning is an important measurement to determine the utilization of straw resources. Understanding the decomposition process and nutrient release process of straw is of great significance to the efficient utilization of straw resources and the sustainable development of the agricultural economy. In this study, the literature published in the CNKI and WOS from 2002 to 2022 was used as the data pool, and a keyword co-occurrence network map was drawn with the CiteSpace (6.2.R4) software. Visual analyses were based on the straw returning literature (1998 articles) and straw decomposition agent literature (125 articles), and the decomposition and nutrient release of straw under the action of a decomposition agent were analyzed using a straw decomposition characterization experiment. In general, returning straw can effectively improve soil fertility conditions and provide nutrients for crop growth, and the use of a straw decomposition agent can further improve soil conditions and increase crop yield. The straw decomposition characterization experiment further showed that Pseudomonas could effectively increase the decomposition rate and increase the nutrient release rate of straw. According to the above results, determining how to improve the utilization efficiency of straw resources via decomposable bacteriological agents according to local conditions will become a research hotspot in the future.

Straw mulching is an important strategy for regulating soil moisture, nutrient availability, and thermal conditions in agricultural systems. However, the mechanisms by which the mulching period, thickness, and planting density interact to influence yield formation in wheat–soybean rotation systems remain insufficiently understood. In this study, we systematically examined the combined effects of straw mulching at the seedling and jointing stages of winter wheat, as well as varying mulching thicknesses and soybean planting densities, on soil properties and crop yields through field experiments. The experimental design included straw mulching treatments during the seedling stage (T₁) and the jointing stage (T₂) of winter wheat, with soybean planting densities classified as low (D₁, 1.8 × 10⁵ plants·ha⁻¹) and high (D₂, 3.6 × 10⁵ plants·ha⁻¹). Mulching thicknesses were set at low (S₁, 2830.19 kg·ha⁻¹), medium (S₂, 8490.57 kg·ha⁻¹), and high (S₃, 14,150.95 kg·ha⁻¹), in addition to a no-mulch control (CK) for each treatment. The results demonstrated that (1) straw mulching significantly increased soil water content in the order S₃ > S₂ > S₁ > CK and exerted a temperature-buffering effect. This resulted in increases in soil organic carbon, available phosphorus, and available potassium by 1.88−71.95%, 1.36−165.8%, and 1.92−36.34%, respectively, while decreasing available nitrogen content by 1.42−17.98%. (2) The T₁ treatments increased wheat yields by 1.22% compared to the control, while the T₂ treatments resulted in a 23.83% yield increase. Soybean yields increased by 23.99% under D₁ and by 36.22% under D₂ treatments. (3) Structural equation modeling indicated that straw mulching influenced yields by modifying interactions among soil organic carbon, available nitrogen, available phosphorus, available potassium, bulk density, soil temperature, and soil water content. Wheat yields were primarily regulated by the synergistic effects of soil temperature, water content, and available potassium, whereas soybean yields were determined by the dynamic balance between organic carbon and available potassium. This study provides empirical evidence to inform the optimization of straw return practices in wheat–soybean rotation systems.