Characteristics Of Soil Fertility And Evaluation Of Land Capability In Dongan County Based On 3S Technique

Soil fertility is the comprehensive reflection of its nature, its level will be directly influence the crops growth, agricultural production structure, composition and benefit; The index of soil fertility is an important factor of reflecting soil fertility and the foundation of evaluating the fertility of the cultivated land. To reveal the characteristics of the soil fertility and the spatial distribution of soil properties, the research was carried out using the methods of field investigation, laboratory analysis, mathematical model, "3S" technique in Dongan County, Hunan Province. Natural factors evaluation methods were used for farmland grading soil classification and evaluation. The major results are as follows:1.The content of soil organic matter was in the high level, its average was 36.2g/kg,where between 30 and 40 g/kg was by 41.53%, higher than 40 g/kg was by 37.9%, less than 20 g/kg by 1.77%.The total nitrogen was in middle-better level, its average was 1.85g/kg, where between 2.0and 3.0 g/kg was by 47.45%, higher than 3.0g/kg was by 6.66%, less than 1.0 g/kg by 4.77%.The available nitrogen was in high level, its average was 189.5 mg/kg, where between 150 and 200 mg/kg was by 42.5%, less than 90 mg/kg was by0.56%, higher than 200 mg/kg by 44.22%. The total phosphorus was in medium level, its average was 0.64g/kg, where between 0.45and 0.85g/kg was by 88.17%, higher than 1.0 g/kg was by 1.47%, less than 0.45 g/kg by 6.49%.The available phosphorus belonged to middle level, its average was19.7 mg/kg, where between 10 and 20 mg/kg was by 59.14%, less than 5 mg/kg was by0.94%, higher than 30 mg/kg by 8.09%. The total potassium was in medium level, its average was 11.8g/kg, where between 12 and 18g/kg was by 40.1%, higher than 25 g/kg was by 1.0%, less than 12 g/kg by 53.8%.The available potassium was in low degree, its average was 86.3 mg/kg, where between 50 and 120 mg/kg was by 83.78%, higher than 200 mg/kg was by 1.0%, less than 50 mg/kg by 5.82%. The slowly available potassium was in low degree, its average was 148.0 mg/kg, where between 90 and 180 mg/kg was by 81.98%, less than 90 mg/kg was by 2.37%, higher than 370 mg/kg by 0.29%.2. The content of organic matter, nitrogen, phosphorus and potassium had different distribution area in different towns. The content of organic matter higher than 30g/kg was mainly distributed in Forest park and Chuanyan towns. The content of total nitrogen higher than 2.0g/kg was mainly distributed in Forest park and Zixishi towns. The content of available nitrogen higher than 150mg/kg was mainly distributed in Forest park and Huannitong forest towns. The content of total phosphorus higher than 0.85g/kg was mainly distributed in Xianyuanzhongchang towns. The content of available phosphorus higher than 20mg/kg was mainly distributed in Xianyuanzhong chang and Huannitong forest towns. The content of total potassium less than 18g/kg was mainly distributed in Jintouyu and Luhongshi towns. The content of available potassium less than 120mg/kg was mainly distributed in Jintouyu and Duanqiaopu towns.The content of slowly available potassium less than 180mg/kg was mainly distributed in Jintouyu and Luhongshi towns.3. Basing on the evaluation principles, a indicator system of Dong county soil capability assessment was established, which including:topography sites, obstacle factors, texture, organic matter, soil available Phosphorus, slowly available Potassium, discharge ability, irrigate ability, Structure Profile, thickness of Topsoil layer. Using fuzzy comprehensive evaluation model, the result showed that the farmland productivity level of Dongan county was in middle level. Its mainly level was third degree, the fourth degree and fifth degree orders. And the third, the fourth and the fifth degree order was by 9.8%,15.0% and 24.9%., respectively. The first degree land was mainly distributed in city of Luhongshi, Zixishi and Dmiaokou town. The second degree land was distributed in all villages of county. The sixth and seventh degree land was mainly distributed in villages except Xianyuanzhongchang and Forest park town.4. Through the evaluate result of cultivated land in Dongan county statistically analyzed with the single factor, the results showed that the mainly restricting factors of farmland productivity of Dongan were slowly available potassium, t thickness of Topsoil layer and soil texture, and second is the irrigation ability and drainage ability.