| Cultivated land is the essence and irreplaceable resource for agricultural production, and it is also the important resource for sustainable development of our society and national economy. Favorable natural cultivated land quality and rational utilization of resources are important foundation and critical condition for regional agricultural and social-economic sustainable development. Therefore, it is of great significance to know the quantity, quality and changes of cultivated land for the reasonable planning, utilization and effective protection of cultivated land. Dynamic study of cultivated land fertility makes it possible to master the fundamental productivity variation of the cultivated land and provide a scientific basis for rational land utilization, soil fertility protection and improvement, cunrrent agricultural production, and related policy decision.Taking Guangrao County as the research area, this paper aims to study dynamic changes, improvement and utilization of cultivated land at county level based on GIS data analysis and fertility evaluation in 2005 and 2007.The research firstly identified grading distribution of cultivated land in Guangrao County. Overlay method between soil map and land use map was adopted to produce evaluation units, evaluation factors were chosen by Delphi approach and cluster analysis with their weights determined by AHP method. Finally the grades of cultivated land fertility were evaluated by fuzzy discrimination method. Our results showed that the cultivated land fertility in Guangrao County was good in general with area of the first and the second grades 60.11% of the total area, the third and the fourth grades 25.68%, and the fifth and the sixth grades only 14.21% of the total area. By means of comparing two period cultivated land fertility evaluation of 2005 and 2007, analysis unit of cultivated land fertility was obtained firstly by superimposing polygon intersection in overlay analysis of GIS.Then comprehensive index of cultivated land fertility and nutrient content changing situation of soil in 2007 were analyzed by using statistical function of GIS regarding 2005 of Guangrao as the base period. Based on classification method of natural distance, the variation was quantitatively classified into five levels, namely becoming better, appreciably becoming better,invariable,appreciably becoming worse and becoming worse. On the basis of this, five level soil fertilities were counted and analyzed respectively and some reasonable countermeasures were put forward. The results show that cultivated land fertility gradually meliorates and main nutrient content gradually increasing in Guangrao County. The area proportion of becoming-better, invariable and becoming-worse cultivated land fertility is 45.45%, 32.73% and 21.82% respectively. The area proportion of increased, invariable and decreased soil organic matter content is 49.81%, 25.39% and 24.80% respectively. The area proportion of increased, invariable and decreased soil available phosphorus content is 66.37%, 19.95% and 13.68% respectively. The area proportion of increased, invariable and decreased soil available potassium content is 55.94%, 25.97% and 18.09% respectively. The study of cultivated land fertility provided basic data for scientific and effective fertilization, changed the situation that farmers fertilized blindly and excessively, which is meaningful for planning and soil utilization of agricultural department.The cultivated land improvement zone was divided based on cultivated land fertility evaluation data in 2007. Firstly, limiting factors of cultivated land improvement were selected, secondly, zoning standard in cultivated land improvement was estibulished, and finally, using the cultivated land evaluation unit, the cultivated land improvement zone types were dertermined by searching corresponding library properties according to the zoning standard of dominant factors in cultivated land improvement. The zoning maps were generated by map surface edition and area ratio of every type was acquisited by statistical analysis. Our results showed that the cultivated land improvement zone in Guangrao County was divided into three types. It included the soil fertility improvement zone, the natural environmental conditions improvement zone and the soil remediation improvement zone.The area of soil fertility improvement is 28.33% of the total area and unimprovement zone is 71.67%; The area of natural environmental conditions improvement zone is 44.23% of the total area and unimprovement zone is 55.77%; The area of soil remediation improvement zone is 37.95% of the total area and unimprovement zone 62.05%.This research presented the whole cultivated land improvement condition in Guangrao County, provided the corresponding solution and positive instruction of rational fertilization for farmers and scientific management for policymakers.This study realized GIS supported cultivated land fertility evaluation, dynamic analysis,improvement and utilization. It proved that the application of GIS technology in cultivated land fertility evaluation, dynamic analysis, improvement and utilizaton is feasible and scientific. Therefor, it provides the technical scheme for the cultivated land fertility evaluation, dynamic analysis, improvement and utilizaton and has application values for scientific management and sustainable utilization of the cultivated land resources.
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