Effects of water and N-fertilizer supplies on the distribution and use efficiency of water and nitrogen of drip-irrigated tomato in greenhouse

Abstract: This study explored the optimal mode of drip fertigation system of tomato in greenhouse in Yangling, China (109°06'E，36°18'N). Three factors with three levels each were considered including drip irrigation pipeline layout, fertilizer-N application rate and irrigation amount. Three pipeline layout included single-plant row, two-plant row and three-plant row of one pipeline. Three irrigation amounts were 50%ET0, 70%ET0 and 90%ET0 (potential evapotranspiration) and ET0 was calculated based on Penman-Monteith modifier formula. Three fertilizer-N amounts were 120, 180 and 240 kg/hm2. The experiment was carried out in 2018 following the orthogonal test design. During the experiment, soil moisture content and nitrate nitrogen content were determined. Water use efficiency and fertilizer utilization efficiency were calculated. The results showed that the drip irrigation pipeline layout, irrigation amount and fertilizer-N amount had different effects on soil moisture content distribution, nitrate nitrogen, tomato yield and water use efficiency and nitrogen utilization efficiency of greenhouse tomato. The distribution of soil water content in different drip irrigation pipeline layout was basically the same, the water content of the surface layer (0-20 cm) was lower and higher in the soil layer of 20-40 cm. The soil water content below 40 cm depth was decreased. The soil moisture content was low in the area far from the emitter but high in the area around the emitter.The moisture content distributions of single-plant row of one pipeline and two-plant row of one pipeline were much uniform than that of three-plant row of one pipeline. The soil nitrate nitrogen (NO3-N) content decreased generally with the soil depth, and the mean value of the nitrate nitrogen content in the 0-30 cm soil layer was greater than that at 30-60 cm. The maximum value of nitrate nitrogen content was 24.96 mg/kg in the 0-30 cm soil layer, and it was 16.71 mg/kg in the 30-60 cm soil layer. Under the same fertilizer-N treatment, the nitrate nitrogen content at the center of the test pit in the 0-30 cm soil layer was larger in the treatment of two-plant row of one pipeline mode than that in single-plant row and three-plant row of one pipeline. It would be conducive to the absorption and utilization of nitrogen by roots. The irrigation amount had an extremely significant effect on the yield of tomato. The fertilizer-N amounts had a significant effect on the yield. The tomato yield was not significantly different for the treatments of irrigation amount of 70%ET0 and 90%ET0, and both treatments were significantly higher than that with the irrigation amount of 50%ET0. The irrigation amount and fertilizer-N application rate had significant effects on water use efficiency and partial nitrogen productivity. The optimized mode of drip fertigation with high yield of tomato was two-plant row of one pipeline, irrigation amounts 70%ET0 and fertilizer-N application rate of 240 kg/hm2. Considering the high efficiency of irrigation water utilization and N-fertilizer partial factor productivity, the optimal combination mode of drip fertigation on tomato was two-plant row of one pipeline, irrigation amounts 70%ET0, N-fertilizer amounts 180 kg/hm2 and two-plant row of one pipeline, irrigation amounts 70%ET0 and N-fertilizer amounts 120kg/hm2, respectively. The result can provide some technical guidance for the production practice of the greenhouse tomato drip fertigation.