Effects of different irrigation and fertilization practices on nitrogen leaching in facility vegetable production in northeastern China

Excessive nitrogen fertilizer and irrigation in facility vegetable production cause N leaching, which leads to a series of environmental problems. It is urgent to develop practical management strategies to reduce N leaching while maintaining or increasing yield and water use efficiency (WUE). In the present study, a greenhouse experiment was conducted in the mollisols of northeastern China, where eggplant was planted as the main vegetable. We aimed to evaluate the effects of different fertilization and irrigation practices on N leaching, eggplant yield and WUE. Four treatments were set: applying regular amounts of fertilizer and irrigation (WF), reducing chemical fertilizer application rates by 20% (W80%F), reducing irrigation by 20% (80%WF) and adding biochar into the WF treatment (WF + B). The results showed that the WF + B treatment significantly decreased N leaching while increasing eggplant yield and WUE by 5.5% and 11%, respectively, in comparison with the results of the WF treatment. The amount of N leaching, eggplant yield and WUE in the W80%F treatment were quite similar with those in the WF treatment. Compared with the WF treatment, the 80%WF treatment significantly decreased N leaching and increased WUE; however, it casued a sharp decrease in yield. Our results demonstrated that adding biochar may be a good practice for minimizing N leaching and increasing yield and WUE in facility vegetable production systems.