Field Experimental Study on the Distribution of Farmland Soil Nitrate Nitrogen in Hebei Plain

Soil nitrate nitrogen observation experiment was conducted in wheat-corn field to analyze the migration law combined with some factors such as irrigation,rainfall,and soil properties.The results showed that soil nitrate nitrogen deep leached obviously,and the utilization rate of nitrogen fertilizer was low in conventional fertilization pattern.The annual variation tendency of soil nitrate nitrogen was sinusoidal curve and the content of soil nitrate nitrogen in wheat was higher than that in corn.The soil nitrate nitrogen content presented in bimodal form in the corn growth period,with the smaller peak(47.75mg/kg)appearing in about 60cm of soil profile and the larger peak(93.72mg/kg)in about 160cm of soil profile. The content of soil nitrate nitrogen below root layer increased as the result of deep leaching,which threatened groundwater environment greatly.