Quality Evaluation Of Cultivated Land In Changsha City

Quality of cultivated land is an important index to reveal production capacity of cultivated land,while quality evaluation of cultivated land shows the important significance on remitting the contradiction between abandonment severity and food security,the contradiction between pursuit of economic benefits and sustainable environmental health,and the contradiction between “domination for weakness” and cultivated land protection.To develop quality evaluation of cultivated land in Changsha City can determine the quality status of cultivated land in Changsha City,find out primary problems in cultivated land utilization and provide the powerful support for the subsequent cultivated land construction.Research data came from the database of land use status in 2017.Cultivated land surface soil sampling points were collected.GIS and cultivated land resource management information system were applied to superpose the soil map,land use map and administrative map to generate the unit map of cultivated land resource evaluation.The quality evaluation model of cultivated land in Changsha City was constructed from six aspects,including health conditions,profile property,site conditions,physical and chemical properties,farmland management and soil nutrient.Fuzzy mathematic theory and analytic hierarchy process were used to determine membership and weight of each index.The summation was applied to calculate the quality index of integrated cultivated land for each cultivated land evaluation unit.Finally,the summation curve was used to divide the quality grade of cultivated land in Changsha City.The evaluation results showed that: By referring to quality standards of cultivated land,quality of cultivated land in Changsha City was divided into ten grades,especially for fourth grade land and fifth grade land,which respectively accounted for 21.70% and 26.45% of total cultivated area in Changsha City,followed by sixth grade land and third grade land,which respectively occupied 20.52% and 10.58% of total cultivated area.The third one referred to the seventh grade land and eighth grade land,which respectively occupied10.52% and 4.61% of total cultivated area.The fourth one included the second grade land and ninth grade land,which respectively accounted for 3.21% and 1.30%.The first gradeland and the tenth grade land had the minimal area,which respectively occupied 0.76% and0.35%.In Changsha City,the land from the first grade to third grade belonged to the high-yield field and gave priority to the plains and hills.The soil pH was weak acid.Organic matter,available phosphorus and rapidly available potassium had the higher contents.It basically had accessible layer and showed the good irrigation and discharge conditions.The land from the fourth grade to the sixth land belonged to the middle-grade cultivated land and showed the general production level.It was distributed in hills and flat areas and had the lower soil nutrition contents.Organic matter maintained the high level,but available phosphorus and rapidly available potassium had the lower contents and good character.Some cultivated land stain latent and acidification.The capacity of preserving moisture and fertility in soil was general.The cultivated land had unbalanced nutrient and poor drainage capacity.The land from the seventh grade to the tenth grade belonged to the low level cultivated land in Changsha City and had poor production conditions.Comparing with the high-yield and middle-yield land,the land from the seventh grade to the tenth grade had the poor irrigation capacity,and the lower soil organic matter.The rapid available potassium contents were obviously reduced,while available phosphorus was inadequate.