N and P runoff losses in China's vegetable production systems: Loss characteristics, impact, and management practices.

Vegetable production systems involve the use of high rates of fertilizer application, leading to significant losses of nitrogen (N) and phosphorus (P) to the environment, resulting in water body eutrophication through surface runoff and leaching. We here quantify, at the national level, total N and P runoff losses and the key factors controlling runoff in open-field vegetable systems in China, by summarizing data from 151 publications pertaining to 13 Chinese provinces using literature dating back to 1990. Rank analysis was employed to clarify the impact of N and P runoff losses in vegetable systems, and different strategies for controlling N and P entering into water bodies are being compared. Vegetable production systems have higher fertilizer inputs (264.3 kg N ha-1, 101.0 kg P ha-1) compared with upland crop and rice cultivation. As a result, annual total nitrogen (TN) and total phosphorus (TP) losses via runoff from vegetable systems reached 16.5 kg ha-1 and 3.45 kg ha-1, respectively, and the N and P loss ratio for fruit vegetable systems reached 13.1% and 3.95% of the total fertilizer input, respectively. In the summer-autumn growing season, soil nutrient losses were the highest, accounting for 44% to 89% of the whole year. Redundancy analysis revealed that the most critical factor determining runoff losses was runoff volume. N and P runoff losses were also largely dependent on total soil N (TSN) and Olsen-P, respectively. Therefore, quantitative data for the national N and P runoff losses in vegetable production systems provide a scientific basis for an effective optimization of fertilizer applications.