The Study Of Spatial Variation Of Soil And Evaluation Of Cultivated Land Productivity In Qianjiang County

Soil has a high variability in time and space, which has continuous, non-homogeneous changes in the body, the major influencing factors include parent material, topography, climate, biology, time and human factors.Today, the farmers mostly cultivated in accordance with the traditional cultivation habits, neglected of the soil variability, and treated land as a unified homogeneous farming unit and made a large area of fertilizer production. This farming method not only made the fertilization lack of specificity, which lead to imbalance withnutrient supply and inefficient fertilizer use; alsocrop yield was not high for fertilizer misuse and serious pollution of arable land.Therefore, to achieve the sustainable use of soil resources, we must fully correct understanding the situation of the spatial variability of soil properties, to understand the relationship between soil nutrients and the quality of arable land, to divide the cultivated land grade correctly, and ultimately to achieve scientific management as "adjust measures to local conditions","right crop for right time "and" specific content".We take the soil nutrient of cultivated land in the region of Qianjiang District for the study, discussing the spatial variable regularity and quality of arable land evaluation of indicators of soil nutrient, to master the spatial distribution and the overall quality of farmland soil fertility, proving data base for soil testing and fertilizer project in Qianjiang District, and to provide the decision making for rational fertilization and improvement in the quality of the soil. Research conclusions are as follows:(1) The pH range for the region is between3.8-8.6,an average of5.61,indicating that the soil of the study area appear acidic; the content of organic matter is between2.1-39.6g/kg, for an average of20.88g/kg effective phosphorus content is0.8-49.8mg/kg,or an average of15.43mg/kg;potassium content is9.0-235mg/kg, or an average of107.95mg/kg. The coefficient of variation among pH, organic matter, phosphorus, potassium are:17.97%,29.64%,57.64%,36.93%, respectively, all belongs to the moderate variability. The coefficient of variation of phosphorus is maximum, showed that the variability of soil phosphorus is maximum; the coefficient of variation of pH is minimum, indicating that the soil pH variation least. The order of the variability above is available P> available K> organic matter> pH.(2) The nugget effect values of pH, organic matter, available phosphorus, available potassium were59.4%,70.5%,91.7%,66.1%respectively pH, organic matter and potassium have a moderate spatial autocorrelation is the result of combined action for structural factors (such as soil formation factors) and stochastic factors (such as fertilizer farming); only available phosphorus has a weak spatial autocorrelation, random factors account for the leading causes of variation.(3) In comparison, the inverse distance weighted interpolation is optimal among the four interpolation.The four indicators of soil characteristics are all use the inverse distance weighted (P=2) interpolation when the RMSE is the smallest.(4) Use of land statistical analysis modulein the Arcgis9.3, derived from the above-mentioned interpolation accuracy, we got the suitable for all soil properties according to analysis of the optimal interpolation method, having spatial interpolation respectively. And make the paddy fields and dry land evaluation unit separately for statistic grading.(5) Statistieal analysis on the level erea of paddy field and dry land.For the paddy land, the area of different grade showed in the order of the first grade land> the second grade land> the third grade land> the fourth grade land> the fifth grade land.For the dry land, the area of different grade showed in the order of the third grade land> the second grade land> the fourth grade land> the first grade land> the fifth grade land.(6) Take sample points of field trials from2007to2008, to validate the evaluation results and verify if they compliance with the actual situation of the study area. The paddy field is divided into a high level, middle level, lower level of verification, dry land make the same with paddy fields for each level select two points. The verification results show that the result of this evaluation is consistent with the actual situation.