The Characteristics Of The Cultivated Soil Fertility Quality And Its Evaluation In Liling County Based On GIS

Liling is an economically more developed County in the middle reaches of Xiang River in Hunan province, belonged to the typical double seasonal food and oil area in subtropical hilly regions, where the agriculture production was more developed. The characteristics of the cultivated soil quality were studied with the field investigation, laboratory test, GIS, GPS and the computer techniques since 2006, due to the related study was a few after the second nation-wide soil survey. The main results showed as follow:1. The soil was acidity, pH average was 5.21, where between 4.9 and 5.5 was by 63.4%, less than 4.5 was by 1.71%, higher than 6.5 by 1.63%. The soil organic matter was higher, its average was 38.1 g/kg, where between 30 and 40 g/kg was by 45.3%, higher than 50 g/kg was by 10.1%, less than 20 g/kg by 1.9%. The available nitrogen was higher, its average was 217.5 mg/kg, where between 150 and 300 mg/kg was by 92.4%, less than 150 mg/kg was by 5.4%, higher than 300 mg/kg by 2.1%. The available phosphorus belonged to middle-better level, its average was 22.0 mg/kg, where between 10 and 20 mg/kg was by 38.9%, less than 5 mg/kg was by 2.9%, higher than 40 mg/kg by 12.0%. The available potassium was middle -low degree, its average was 106.2 mg/kg, where between 30 and 90 mg/kg was by 49.0%, higher than 150 mg/kg was by 17.1%, less than 30 mg/kg by 0.7%. The slowly available potassium was lower, its average was 151.1 mg/kg, where between 60 and 120 mg/kg was by 43.7%, less than 60 mg/kg was by 3.4%, higher than 300 mg/kg by 7.4%. Compared with the second soil survey, the decreased trend of soil pH was observed, the soil available nitrogen, available phosphorus and available potassium increased, while the increment of the available phosphorus was greatest, that of the available nitrogen was less.2. Throught analyzed the various soil fertility parameters in Liling county using the traditional statistics, geo-statistics and GIS, the results showed the pH variation coefficient was at the weak variation level, and the available nitrogen, soil available phosphorus, available potassium, slowly available potassium and the organic matter was at the medium variation level. The available nitrogen nugget was largest, while the others were relatively smaller. The substrate effect of the available nitrogen, soil available phosphorus, available potassium, slowly available potassium, pH and the organic matter was from 25% to 75%, its system spatial correlation was at the medium level. The fitting theory model of the soil pH, the available nitrogen, soil available phosphorus, available potassium, slowly available potassium and the organic matter were the exponential model.3. The temporal variation of the soil fertility parameters was studied using the geo-statistics and GIS, the results showed the soil pH of Liling was generally the middle-class stability MI level, the soil available nitrogen was the middle-class stability MIII level, while the available potassium and available phosphorus was the middle-class instability UIII level.4. The evaluation index system of cultivated land productivity was builted, baseing on the principle of the indexes selected, included topography sites, obstacle factors, texture, organic matter, soil available Phosphorus, slowly available Potassium, discharge ability, irrigate ability, Structure Profile, thickness of tilth layer. The cultivated land productivity was evaluated using the subjected function, the level analytic method and experimental method and the fuzzy comprehensive evaluation model, the results showed the farmland productivity level of Liling county was much higher, mainly was the first or second orders. The first orders were mainly distributed in the village of Shiting, Junchu and Banshan, and the second orders were mainly in the village of Dongfu, Sifen and Banshan, the sixth orders were mainly distributed in the village of Baitutan, and the seventh were all in Nanqiao.5. The evaluate result of cultivated land in Liling county statistically analyzed with the single factor, the results showed the mainly restricting factors of farmland productivity of Liling included slowly available potassium, thickness of tilth layer and soil texture, and second is the ability to irrigation and drainage.