| Nitrogen is essential to life on earth all the ingredients, which exist in many organic molecules. In crop production, crop nitrogen requirements of the larger lack of soil nitrogen supply is decreased and the quality of agricultural products caused by lowering the main limiting factor. Excess nitrogen fertilizer application at the same time will cause rivers and lakes, eutrophication, groundwater nitrate accumulation and poisoning. Understanding of nitrogen cycling in modern agriculture and environmental protection faced challenging questions. Nitrogen content in soil by natural factors such as parent material, vegetation, temperature and precipitation, but also by human factors such as the use patterns, tillage, fertilization and irrigation measures. Evaluation of soil fertility and soil nitrogen is an important indicator of soil quality is an important global carbon cycle sources and sinks of soil nitrogen has become the current soil science, environmental science research hot spots. Based on the surface(0-20cm)of the 80 counties, the determination of soil total nitrogen .Analysis of soil total nitrogen of Gansu Province, the space changes and with the climatic factors, land-use changes in the type of trend. Give the following findings:1. Soil total nitrogen from south to north as the latitude there was a downward trend in Gansu, Soil total nitrogen in surface and latitude significant negative correlation Soil total nitrogen is Non-significant change in longitude. Gansu Province, north and south with a flat east-west strip of the terrain, south-west north-eastern low-lying high and complex characteristics of a variety of landforms. Counties in Gansu Province of the average levels of soil total nitrogen with a clear vertical distribution, with the increase in altitude polar surface soil total nitrogen significantly increased, y=0.0007x-0.3254,and a correlation coefficient of 0.618.2. Climate directly affects the soil hydrothermal condition and the physical, chemical process, the nature and intensity of soil total nitrogen by the impact of climate change significantly in Gansu. Soil total nitrogen in 80 counties with the annual average temperature decreased, both were highly significant negative correlation, y=-0.1291x+2.1711,a correlation coefficient of -0.421. The content of soil total nitrogen increased with increasing rainfall trend, y=0.001x+0.7057,a correlation coefficient of 0.227, p=0.043. 3. Different land use patterns of soil total nitrogen in Gansu is grassland > forest land > cultivated land > unused land. Grassland, woodland was significantly higher than that of cultivated land and unused land. This is the type of soil, the texture of soil, light intensity, vegetation type, microbial activity of a great relationship.4. The exception of six eco-regions in the Loess Plateau of East Gansu Hexi Corridor and soil total nitrogen were Non-significant differences, the other ecological regions of soil organic matter have a significant difference. Gannan plateau significantly higher than the remaining five regions, and 3.8 times of Hexi Corridor and3.7 times of Loess Plateau of Longdong; Qilian Mountains is 3.7 times of Hexi Corridor and 3.6times of the Loess Plateau of Longdong; the lowest soil total nitrogen content in the Hexi Corridor.Ecological region in six different land use types of soil total nitrogen status: Gannan Plateau ,Longxi Loess Plateau of grassland soil total nitrogen was significantly higher than that of arable land, forest land and unused land, but cultivated land and unused land were Non-significant differences between; Longnan mountain forest was significantly higher than that of arable land; the Hexi Corridor, Gansu Longdong plateau of forest land soil total nitrogen was significantly higher than that of arable land, grassland and unused land ; Qilian Mountains to the four kinds of land-use types of soil total nitrogen no significant difference.
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