Spatial Variability Of Soil Nutrients And Evaluation Of The Farmland Productivity In Guanghe County Based On GIS

The farmland productivity soil sampling data of2009and the second national soil survey data of1987were selected as the foundation data, and to study the spatial and temporal variation of the soil surface soil organic matter, total nitrogen, effective phosphorus and available potassium in guanghe county of Gansu province. The main purpose of this study was to explicit the change of cultivated land quality for guanghe county in the latest20years meanwhile to evaluate the cultivated land quality.Main results are as follows:1、Compared with the second soil census in1987, the content of soil organic matter, total nitrogen, available phosphorus and available potassium had a increased tendency. One of the main reasons was that the application of organic fertilizer and chemical fertilizer had increased significantly to ensure and increase the grain production in recent years, besides, the amount of crop residues and the root crops returned were also increased. Therefore overall statistics shown that the soil nutrient content for guanghe county was increased.2、 The semivariance analysis of soil organic matter and nutrients in2009was conducted with the statistical methods. The optimal model for soil organic matter, available phosphorus and available potassium were spherical, for total nitrogen was exponential model. According to partition criterion of Cambardella’s:if the ration between Nugget and Sill was16.67%it showed a strong spatial dependence. Structural factors (such as parent material, topography, climate and soil types) could make soil nutrients have strong spatial dependence in a large extent OM、TN、 AK’s Nugget/Sill was30.38%,42.57%and36.03%respectively, they showed them had medium spatial intensity dependence, which implied the variation was affected by the combined action of random factors and structural factors, random factors included cultivation, fertilization and cropping system, etc.3、 Farmland productivity of Guanghe County was divided into four levels by farmland productivity index method. The area of four classes arable land was3897.0hm2,5222.4hm2, 6206.6hm2and3188.8hm2respectively, taking up21.1%,28.2%,33.5%and17.2%.This study shows that the soil quality and the farmland productivity overall showed a trend of ascending simultaneously in the past20years. Cultivated land quality evaluation result provided a reliable basis to improve cultivated land quality and productivity for the township zoning classification for guanghe county’s soil management.