Over-application of nitrogen is widespread in greenhouse vegetable production in China and induces environmental problems. The nitrogen leaching lose from unsuitable irrigation has proved to be the bottleneck of reducing nitrogen application, and timely and adequate irrigation so became one of the key countermeasures for reduction of nitrogen application. This experiment was conducted to schedule irrigation with tensiometers and pan evaporation, probing the effects of that on tomato (Lycopersicon esculentumMill) fruit yield and soil nitrate. The results show that i) when Kcp=1.2, tomato obtain high yield while Kcp=0.4 or 0.8, the corresponding irrigation cannot meet plant need for water and lead to yield reduction, and ii) comparing with conventional irrigation, pan-evaporation-based irrigation schedules significantly reduce the amount of irrigation water to deeper soil layers, thereby limiting nutrient in soil solution downward, which results in much lower NO3-N content in subsoil and greatly mitigate the risk of nitrate leaching loss.
