Effects of Land Use and Topographic Factors on the Variability of Soil Nutrients in Newly Reclaimed Area in Yili

The spatial variability of soil nutrient may be influenced by environmental factors. Based on the data of measured section in the field and laboratory analysis, this study has explored the effects of land use and topographic factors on the distribution characteristics of surface soil nutrients on the scale of sampling points with the mathematical statistics method. The results show that: 1) Land use types have significant effects on the organic matter, total nitrogen and total phosphorus of the surface soil but have slight effects on total potassium. Saline land contains the most organic matters while sand contains the least. Total nitrogen in wasteland is less than that in farmland. As for the total phosphorus, saline land has the highest average content and moderate coverage grassland has the largest coefficient of variation; 2) Different topographic factors affect the soil nutrients to different degrees. The four soil nutrients are positively correlated with altitude, they have the lowest average content at the altitude gradient of 500～600m and the largest fluctuation range at the altitude gradient of 600～700m. The average content of organic matter, total nitrogen and total potassium at high altitude gradient is higher than that at low altitude gradient. Nevertheless, the average content of total phosphorus presents inverted-U distribution with the rise of the altitude; 3) Organic matter and total nitrogen included in the soil are positively correlated with slope. The average content of them above the slope of 3° is obviously higher than that under the slope of 3°. When the slope gradient is less than 1.82°, the average content of the four soil nutrients shows the largest fluctuation range. 4) Total phosphorus is negatively correlated with the slope direction. The average content of the soil nutrients on the shady slope is higher than that on the sunny slope. However, except total potassium, the other three soil nutrients have larger fluctuation ranges on the sunny slope than they do on the shady slope; 5) The interaction between land use types and topographical factors has effect on the nutrients content of surface soil. Soil organic matter content of moderate coverage grassland is obviously higher than that of farmland and low coverage grassland at places with higher altitude, sharper slope and shady slope, but it is the opposite at places with lower altitude, gentler slope and sunny slope.