Simulating nitrate and DON leaching to optimize water and N management practices for greenhouse vegetable production systems

Abstract

Nitrate and dissolved organic nitrogen (DON) leaching are major nitrogen (N) loss pathway for intensive greenhouse vegetable production system (GVPS). Quantifying the nitrate and DON leaching is essential to develop best management practices. In this study, four seasons of tomato field experiments were conducted to test the impact of different water (furrow and drip irrigation) and N management practices and straw incorporation on N leaching and vegetable yield. A soil-crop system model (WHCNS_Veg, soil Water Heat Carbon Nitrogen Simulator for vegetables) was calibrated and evaluated, and results suggested that the model performed well for simulating soil water potential, water drainage, nitrate and DON leaching, crop N uptake, and yield. The average values of NRMSE, IA, and NSE for nitrate (or DON) leaching ranged from 12.1 % (11.3 %), 0.96 (0.94), and 0.85 (0.77), respectively. Compared with furrow irrigation and over fertilization, drip fertigation treatments reduced irrigation water use, water drainage, nitrate and DON leaching by 41 %, 60 %, 68 %, and 68 %, respectively, without compromising crop yield. Straw incorporation further reduced nitrate and DON leaching by 13.1 % and 25.7 % compared with no straw incorporation. Furthermore, we found that DON leaching accounted for 21.7 %–46.6 % of total dissolved N leaching loss in the study area. Using the model, we determined that the optimal water and N inputs ranged from 350−400 mm and 350−400 kg N ha−1 for the winter-spring season and 200−250 mm and 150−200 kg N ha−1 for the autumn-winter season. This led to an 87 % reduction in nitrate leaching and a 74 % reduction in DON leaching with only a slightly reduction in crop yield (<5 %) compared with the local farmer practice. The recommended water and N management practices achieved high crop yield with less environmental impact.