The interest in reusing wastewater for irrigation is being popularized in most countries. The objective of this study was to evaluate the effects of different wastewater and nitrogen fertilizer on soil fertility and plant quality, as well as to identify the optimal irrigation mode in the North China Plain. A total of nine treatments, including control (groundwater, no fertilizer), piggery wastewater, reclaimed water, and saline water, combined with nitrogen fertilizer (300 kg/ha and 200 kg/ha), were conducted in a greenhouse in 2019 (Xinxiang, Henan Province). Soil pH, electrical conductivity, organic matter, heavy metals contents, and cucumber yield and quality were analyzed. The results showed that: (1) compared with the underground water (control), soil pH value with a decrement of 0.21 units in piggery wastewater (PW), and 0.24 units in saline water treatments (SW). Soil electrical conductivity (EC) value significantly increased by 5.8~20.9% in PW and SW treatments, while there was no significant difference in EC in reclaimed water. The highest EC (770 µS/cm) was recorded in SW treatment. (2) No dramatic difference on the concentrations of soil lead (Pb) and cadmium (Cd) in the PW, RW, and SW treatments, compared with the control, but soil organic matter, copper (Cu), and zinc (Zn) concentrations in wastewater treatments were increased by 2.1~43.4%, 24.4~27.0%, and 14.9~21.9%, respectively. (3) There were no significant differences in cucumber yield and quality in RW treatment, while there was a slight decrease by 1.4% in yield in the SW treatment. The highest cucumber yield was observed in PWH treatment, with an increment of 17.5%. In addition, the contents of Vitamin C, soluble sugar, and protein were also improved by PW treatment. In this study, PW treatment showed the strongest ability to promote cucumber yield and quality, thus indicating that piggery wastewater irrigation with 300 kg/ha nitrogen would be the optimal practice in this region. Long-term study is necessary to monitor potential risk of heavy metals on the quality of soil and plant.

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.