Characteristics of nitrate leaching in high yield farmland under different irrigation and fertilization managements in North China Plain

The objective of this study was to provide some suggestions on reducing nitrate leaching from cropland under the intensive cropping pattern in North China Plain. The experiment was carried in a typical high yield production area of Huantai county from 2006 to 2008. Two kinds of irrigations and two kinds of fertilizer N managements were designed, including traditional and optimal irrigation treatments, fertilized with Urea and controlled release fertilizer (CRF). Soil water content and nitrate content in soil solution at the depth of 2 m were observed by tensiometer and ceramic suction cup respectively. The amount of nitrate leaching was calculated by Darcy’s law. The results showed that under the same fertilization condition, quantity of water drainage was obviously reduced optimal irrigation treatment, which was about 50% of that in traditional irrigation treatment. Under the same irrigation treatments, the nitrate content at the depth of 2.1 m soil profile was reduced sharply under the CRF treatment. Irrigation patterns had a insignificant effect on the amount of residual nitrate content in soil profile. The amount of residual nitrate was reduced to 60% of that in the Urea treatment. Compared with the traditional water and N combined management, amounts of nitrate leaching were reduced by 60%, and nitrate leaching ratio was also declined by 50% for the CRF treatment without decreasing grain yield. Thus, the optimal irrigation and N-fertilizer management is recommended.