Temporal And Spatial Variation Of Cultivated Land Quality In Friendship Farm Based On RS And GIS

Cultivated land is the basic resources and conditions for human survival and development.The food security of a country depends on the quantity and quality of cultivated land.The black soil area in northeast China is an important commodity grain base in China,which has the advantages of high soil fertility and strong fertilizer supply capacity,and plays an important role in the national food security strategy.However,in recent years,the black soil resources have been degraded due to natural and human factors,and the quality of cultivated land has been seriously affected.Therefore,it is an urgent problem to monitor and evaluate the quality of cultivated land in the black soil area,strengthen the protection of cultivated land in the black soil area,and improve the quality of cultivated land.Taking Friendship Farm as the study area,this study aims to construct a pixel-based cultivated land quality evaluation model that conforms to the actual situation of the study area by combining GIS and remote sensing technology.The data of soil sampling points in 2005 and 2018 were collected to obtain multi-phase remote sensing satellite images.Combined with 30 m SRTM-DEM data in Heilongjiang Province,from five aspects of site conditions,nutrient status of arable layer,physical and chemical properties of arable layer,soil management and production capacity.Based on the pretreatment of multi-period remote sensing images,the multi-year crop types were divided according to the spectral characteristics of the land,and the standard deviation of NDVI time series data was calculated to characterize the stability of cultivated land use.The weight of each criterion layer and index layer is determined by analytic hierarchy process,and the membership function is constructed to determine the membership degree corresponding to each index value.Based on the data obtained,the cultivated land quality evaluation model of Friendship Farm was constructed,and the comprehensive score of cultivated land quality evaluation was graded.To explore the spatial distribution and temporal and spatial variation of farmland at different levels in farms and management areas;at the same time,the obstacle degree model is introduced to divide the obstacle types of cultivated land quality according to the index obstacle degree,so as to put forward targeted countermeasures and suggestions for the improvement of cultivated land quality.The main research results are as follows :(1)The cultivated land quality of Friendship farm is divided into five grades.In 2005,the cultivated land quality was mainly distributed in the second and third grades,and the average grade of cultivated land quality was 2.59,indicating a good overall level.In 2018,the cultivated land quality was mainly distributed in the second,third and fourth grades,with an average grade of 3.1.(2)Compared with 2005,the cultivated land quality of friendship farm decreased in 2018,and the cultivated land quality grade decreased by 0.51 on average,and the decreased area was larger than the improved area.Different levels of cultivated land are distributed within each management area,and the overall cultivated land quality decreases,showing a change trend from the middle of the farm to the northeast and southwest of the farm.(3)The main obstacle factors of cultivated land quality in Friendship Farm in 2005 were organic matter,available phosphorus,soil texture,irrigation capacity and topsoil thickness.The main obstacle factors of cultivated land quality in Friendship Farm in 2018 were topsoil thickness,available phosphorus,organic matter,soil texture and irrigation capacity.The cultivated land quality in the study area was significantly decreased by the surface layer thickness during 13 years,and the cultivated land quality was significantly improved by the organic matter in friendship farm.(4)During the 13 years,the area of cultivated land with two and one severe obstacle index increased and the area of barrier-free type decreased.In 2005,the main organic matter barrier area;in 2018,the main obstacle area was the thickness of plough layer.According to the types of cultivated land quality obstacles in Friendship Farm,specific countermeasures and suggestions for improving cultivated land quality were put forward.