Effects of drip irrigation system uniformity and nitrogen applied on deep percolation and nitrate leaching during growing seasons of spring maize in semi-humid region

Drip system uniformity is one of the important factors affecting the deep percolation and nitrate leaching under drip-irrigated crops. Field experiments were conducted during two growing seasons of spring maize (Zea may L.) in 2011 and 2012 in North China Plain to evaluate the influence of drip irrigation system uniformity on deep percolation and nitrate leaching under semi-humid conditions. In the experiments, three Christiansen uniformity coefficients of 59, 80, and 97 % (the equivalent distribution uniformity DU values were 57, 71, and 95 %, respectively) and three levels of nitrogen applied at 0, 120, and 210 kg ha(-1) were tested. The results of the study demonstrated that nitrate leaching was most importantly affected by the nitrogen applied, followed by the initial nitrogen content in the soil and the drip irrigation system uniformity. An increasing amount of nitrogen applied and initial nitrogen content increased the seasonal nitrate leaching significantly, while an improving system uniformity decreased the nitrate leaching. The conventional nitrogen application rate of 210 kg ha(-1) could be reduced, and an extremely low drip uniformity of less than 60 % is not recommended to reduce the risk of deep percolation and nitrate leaching in the semi-humid region of North China Plain.