EFFECT OF IRRIGATION AND FERTILIZATION ON NITRATE LEACHING IN LOAMY FLUVO-AQUIC SOIL

Nitrate leaching is not only main reason of low utilization efficiency of nitrogen, but also cause serious environment pollution. So determining nitrate movement and affecting factor in soil profile is the essential prerequisite of preventing nitrate leaching. Therefore long-term.location field experiment for reducing NO3-N leaching was conducted in winter wheat-corn rotation system in Herigshui, irrigation as main treatment and N fertilizer as subtreatment were five levels. The results showed that N application rate was the main factor of NO3-N leaching, there was no NO3-N leaching when N application was below 150kghm-2. but N use at a rate of 225～300kg hm-2 increased NO3-N leaching in winter wheat. There was evident NO3-N leaching during winter when N rate of basal dressing was high in treatment of without irrigation. There was no nitrate leaching irrigated for two times both at jointing stage and milk stage of winter wheat. Rainfall in rainy season resulted in more NO3-N leachirig. Although irrigation at rate of 1350m3 hm-2 had a low NO3-N leaching to the 100～150cm depth,the NO3-N content of soil reduced seriously in the whole profile, it meant that there was more N loss. So irrigation amount should,be controlled at a rate of 450～1050m3hm-2 for each time. Delay irrigation at elongation stage in spring should reduce NO3-N loss. To prevent soil NO3-N leaching in rainy season is very important for reducing NO3-N leaching and pollution to groundwater.