Research on Soil Nitrogen Balance Mechanism and Optimal Water and Nitrogen Management Model for Crop Rotation of Vegetables in Facilities

Vegetable production is an important area of focus in China's agricultural structural adjustment plans, and it serves as one of the essential industries in the rural economy. Several studies have investigated how to optimize vegetable yield and quality through proper irrigation and fertilization to ensure efficient and sustainable development. The main objective of this paper is to examine the impact of different combinations of irrigation and nitrogen inputs on facility-grown vegetables under irrigation and fertilization conditions. Additionally, we aim to identify the optimal irrigation and fertilization regime that can enhance yield quality while also promoting environmental benefits. In this study, we focused on a white radish-tomato facility as the main research object. Using multiple regression and spatial analysis methods, we established three irrigation levels (W1: 100% ET0, W2: 85% ET0, W3: 70% ET0) and four nitrogen application levels (N0: no nitrogen, N1: high nitrogen, locally recommended nitrogen, N2: medium nitrogen, 85% N1, N3: low nitrogen, 70% ET0). We analyzed the effects of an irrigation nitrogen application on vegetable yield, nitrogen bias productivity, soil nitrogen surplus, and integrated N1 warming potential. Our experimental results showed that irrigation volume and nitrogen application had a considerable impact on the yield of facility-grown vegetables, and there was a positive correlation between irrigation water and fertilizer application and yield. By moderately reducing the irrigation volume and increasing nitrogen application, soil nitrogen surplus and nitrogen fertilizer bias productivity can be effectively improved. In addition, our study found that the integrated warming potential and the bias productivity of nitrogen fertilizer showed a quadratic relationship, which indicated that the integrated warming potential and nitrogen fertilizer bias productivity would first become larger and then decrease under the condition of increasing the irrigation volume and nitrogen application rate. By analyzing the difference between W2N2 and W1N1, we found that moderate water-saving and nitrogen reduction did not affect yield. Furthermore, it effectively improved the bias productivity of nitrogen fertilizer. Therefore, it is recommended that when the irrigation volume is between 560 and 650 mm and the nitrogen application rate is between 325 and 400 kg/hm(2) and more than 90% of the maximum value of yield, nitrogen fertilizer bias productivity can be achieved at the same time while also having a lower integrated warming potential. This range of irrigation and nitrogen application intervals is close to optimal. Our study provides a guiding basis for rotational soil nitrogen balance, optimal water, and nitrogen management of facility-grown vegetables. We propose an optimal water and nitrogen management strategy that is more efficient and sustainable under the plant culture model. This strategy provides a new way of thinking and methodology for high-quality production that is water-saving and fertilizer-saving while addressing the water and soil resource problems that exist in the current development of the vegetable industry.