Units Division Of Cultivated Land Evaluation Based On The GIS

It is significant meaning for mastering cultivated land production abilityaccurately, strengthening the quality of cultivated land construction in line with localconditions, guiding the Agricultural Structural Adjustment, fertilizing scientificallyand reasonably and food security through Carrying out the cultivated land fertilityevaluation, setting up the early warning system of the cultivated land quality in ourcountry gradually. In addition,the soil productivity assessment results is a foundationof collocating cultivated land resources scientificlly,improving the cultivated landutilization efficiency,enhancing the sustainable agricultural development.Consequently,it's more important to promote the accuracy and availability of thecultivated land evaluated results.This paper is aiming to provide theoretical referencefor the area soil productivity assessment with carrying out the influence of differentassessment unit to the results. Improve the result of evaluation county the cultivatedland fertility practicality.This paper selected the loess hilly region (QinAn county) and loess plain (LinZecounty) as the research object. Intersetted the digital soil map, present land use mapand administrative map generate the cultivated land resource evaluation units inQinan and Linze county,with merging and not merging small polygons that is lessthan7000m2,15000m2of the evaluated unit data layer respectively, the mergingmethods of three different small polygon produce evaluation units,and that iscompared by the cultivated land fertility evaluation results.The results shows:(1)Taking QinAn county as an example in loess hilly-gully region: the evaluationunit through merging polygon is less than15000m2,because the evaluation unit areais larger, the contribution rate of the physiognomy types as evaluation factors issmaller, impact evaluation results and lead great difference of evaluation result andthe actual situation; because the area of the evaluation units with not merging polygonis too small, designated measuring for data space interpolation can't specific to a verysmall area, thereby affecting the evaluation results.(2) Taking LinZe county as an example in loess plain region: the results is lesseffected by the size of soil productivity assessment units in loess plain region,therefore determining the size of soil productivity assessment units,must considerate the accuracy of soil testing and fertilizing data and the size of countyarea,meanwhile,as possible as not to merger small polygon.The conclusion is:the landforms types of loess hilly-gully region as an importantindex and regional area size jointly decided the size of evaluated units area. In theloess plain region the evaluation result is less effected by the size of cultivated landfertility evaluation units.