Negative-pressure irrigation improves water and fertilizer use efficiencies and fruit yield of greenhouse tomato on the North China Plain*

Water and fertilizer supply are the main factors limiting greenhouse vegetable production on the North China Plain. This study tested the hypothesis that negative-pressure irrigation is advantageous for reducing water and fertilizer application compared with drip irrigation in a greenhouse. Three treatments (drip irrigation + optimal fertilizer [DOF], drip irrigation + Yamazaki tomato nutrient solution [DNS], and negative-pressure irrigation + Yamazaki tomato nutrient solution [NNS]) were applied in a greenhouse tomato double-cropping system conducted in consecutive spring-summer and autumn-winter seasons. Soil moisture content, nitrate-nitrogen (N) concentration, fruit yield, total N uptake (N-u), irrigation water productivity, and partial factor productivity of applied fertilizer were analysed. The seasonal variation of soil moisture and nitrate-N contents in the 0-20-cm soil layer for NNS treatment was stable. Nitrate-N accumulated after the final harvest in the autumn-winter season of NNS treatment was significantly less than under DOF and DNS. Despite lower water and nutrient inputs, NNS showed higher N-u and fruit yield than DOF and DNS. These results demonstrated that negative-pressure irrigation can reduce irrigation water and nutrient inputs and nitrate-N accumulation in the soil, and significantly improve water and fertilizer use efficiency in greenhouse-grown tomato compared with those under drip irrigation.