Simulating the fate of nitrogen and optimizing water and nitrogen management of greenhouse tomato in North China using the EU-Rotate_N model

The objectives of this study were to compare nitrate leaching and gaseous N loss from greenhouse tomato grown under different water and fertilizer management, and to optimize water and nitrogen management practices. A greenhouse experiment with different water and nitrogen management practices was conducted in Shouguang county, northern China, from August 2010 to June 2011. Four treatments were imposed: furrow irrigation + conventional fertilizer (farmer's practice, FP), FP + crop residues (FPR), drip irrigation + optimal fertilizer (DO), and DO + crop residues (DOR). The EU-Rotate_N model was used to simulate tomato growth, water movement and N fate. The simulation results indicated that nitrate leaching and gaseous N loss were the main pathways of N loss in greenhouse tomato production in the study area. The amounts of nitrate leaching under furrow treatments accounted for 43-67% of total N input. Gaseous N loss under all treatments accounted for about 3-14% of total N input. Drip irrigation and optimal N fertilizer application can significantly reduce nitrate leaching and improve water and nitrogen use efficiencies (WUE, NUE). Compared with farmer's practices (FP, FPR), nitrate leaching under drip irrigation (DO and DOR treatments) decreased by about 90%, while the NUEs was increased 2- to 3-fold. In addition, adding crop residues (DOR, FPR) reduced nitrate leaching by 15% compared to the treatments with no crop residues (DO, FP), while it increased the gaseous N loss by about 35%. Furrow irrigation is the most commonly practiced method for most vegetable production in northern China, and this farmer's practice was selected to obtain the best management practices (BMPs) for irrigation schedules and N fertilization rates. More than 288 scenarios combining various types of irrigation and fertilizer practices were simulated per season. Agronomic indices (tomato yield, WUE and NUE), environmental indices (nitrate leaching and gaseous N loss), and economic index (value to cost ratio) were selected as the evaluation indices to identify the BMPs. An osculating value method was used to evaluate combinations of irrigation and fertilizer practices. The results indicated that the BMPs under furrow irrigation conditions are to irrigate tomato with 300 mm and apply fertilizer N at a rate of 150 kg N ha(-1) in the autumn-winter season, and to irrigate with 300 mm and apply fertilizer N at a rate of 250 kg N ha(-1) in the spring-summer season. (c) 2013 Elsevier B.V. All rights reserved.