Effects of Irrigation and Nitrogen Fertilizer Input Levels on Soil NO(3) (−)-N Content and Vertical Distribution in Greenhouse Tomato (Lycopersicum esculentum Mill.)

The purpose of this study is to investigate the interactions between irrigation and fertilizer treatments on soil NO(3) (−)-N content and vertical distribution under drip fertigation in greenhouse tomatoes. Randomized block design with three replications and the treatments consisting of three levels of irrigation and three levels of N fertilizer were used. Three irrigation levels were W1 (100% ET(0)), W2 (75% ET(0)), and W3 (50% ET(0)) and fertilizer levels were F1 (N240–P(2)O(5)120–K(2)O150 kg hm(−2)), F2 (N180–P(2)O(5)90–K(2)O112.5 kg hm(−2)), and F3 (N120–P(2)O(5)60–K(2)O75 kg hm(−2)). The result demonstrates that dynamics of soil NO(3) (−)-N and its response to drip fertigation and levels of N moved toward the fore soil moist, and the average soil NO(3) (−)-N content with W3 treatment was 1.23 times higher than that of the W1 treatment in 0–60 cm at 43 days after transplanting. The negative correlation between N use efficiency and levels of fertilizer N and the N recovery efficiency was increased with increases of N fertilizer application. The fertilizer nitrogen rate greatly significantly influenced soil NO(3) (−)-N content. Avoiding N leaching through controlled matching N fertilizer application and controlled irrigation to tomato N demand is the key to maintain crop yield and improve N use efficiency.