Variations Regularity of Soil Nitrate Nitrogen in Hebei Piedmont Plain

Field experiment was carried out to study on the spatial and temporal distribution of soil nitrate nitrogen at Ranzhuang water resources experiment station in Hebei piedmont plain from 2011 to 2012. The results show that nitrate nitrogen content varies in sinusoidal curve at shallow tilth soil and shows in "W" shape at deep soil profile during the wheat-maize rotation period. Nitrate nitrogen is mainly accumulated in 0~100cm soil and the maximum value occur at reviving stage in the wheat growth period. In the maize growth period, the distribution of nitrate nitrogen is double peak curve in 0~500cm soil profile. The maximum peak emerges at 150~260cm, the peak of soil nitrate content is between 36.7~106.36mg/kg. In 0~500cm soil layers, the cumulative amount of nitrate nitrogen is 1430.56~5126.05 kg/hm 2 . The amount of nitrate nitrogen leaching is 1294.13kg/hm 2 , which is 52.29% of the total amount of annual fertilization. It is scientific and technical groundwork to improve the utilization efficiency of nitrogen fertilizer and protect groundwater environment.