Assessment Of Cultivated Land Quality And Its Obstacle Factors Zoning In The Brown Earth Region

It is seriously threaten to the national food security for China due to the quantitative and qualitative decreases of the cultivated land resources.In general,the quality of cultivated land is determined by the climate,soil conditions and human management.Meanwhile,the soil obstacle factors are the key to assess the quality of cultivated land.Therefore,it is necessary to carry out the evaluation of cultivated land quality from the perspective of soil types and their obstacle factors in order to protect and improve the quality of cultivated land,which will give references for the zoning management of cultivated land resources.In this study,the evaluation of cultivated land quality in the brown earth of Liaoning Province was carried on using the methods of Delphi for selecting evaluation indices and Analytic Hierarchy Process(AHP)for determining the weight of each index.Afterwards,the fuzzy mathematics method was used to comprehensively evaluate the quality of cultivated land of brown earth in Liaoning Province.Moreover,this study introduced the function of obstacle degree to diagnose the indices of cultivated land quality to get the main obstacle factors.According to the primary and secondary order of obstacle degree,the obstacle types of cultivated land quality were divided,and then the measures for improving cultivated land quality have been pointed out.The main results were showed as follows:(1)A cultivated land evaluation index system was established for brown earth and the indices were diagnosed by the obstacle degree model.The method of Delphi was used to select 14 indices in 6 aspects including soil management,physical and chemical properties,soil nutrients,profile characters,site conditions,and climatic conditions.The method of AHP was used to determine the weight of each index.By means of the fuzzy mathematics method,a comprehensive evaluation system of cultivated land quality in Liaoning brown earth was established.Moreover,through the introduction of obstacle degree function,the diagnosis of the quality index of cultivated land was performed,and the main obstacle factors affected the quality of cultivated land in Liaoning brown earth were analyzed.According to the order of the primary and secondary obstacle degree of cultivated land quality,the types of farmland quality barriers were designated.(2)The areas of cultivated land were 1,895,500 hm~2 in brown earth with different regions in Liaoning Province.Ten grades were divided according to the assessment of cultivated land quality of brown earth in Liaoning Province.The first-grade cultivated land was the best in quality and the tenth-grade was the worst relatively.High level cultivated land(including the first-to the third-grade cultivated land),medium level(including the fourth-to the seventh-grade)and low level(including the eighth-to tenth-grade)of cultivated land were accounted for 21.49%,59.18%and 19.33%of the total area of brown earth in Liaoning Province,respectively.The majority of cultivated land was dominated by medium-and low-level cultivated land,which was mainly distributed in the lower plains of the Liaohe Plain and the hills in the north of the Liaoning.(3)The medium-and low-level cultivated land was diagnosed with obstacle degree model based on the evaluation of cultivated land quality.The results showed that the area of cultivated land in the brown earth of Liaoning Province with obstacle factors was 145.67 hm~2.Meanwhile,the main obstacle factors were organic matter,irrigation capacity,drainage capacity,texture and soil profile configuration,in which was showed a decrease order of obstacle degree.To zone the major obstacle factors in the study area,the dominated and the secondary obstacle factors were selected for the zoning analysis by combining obstacle factors.Consequently,the combination types of the obstacle factor zoning were divided into14 in 3 category regions included the organic matter obstacle type region,the irrigation ability obstacle type region,and the texture obstacle type region.These obstacle type regions were accounted for 86.45%,10.75%and 2.80%of the total area of brown earth,respectively.(4)Based on the differences in the types of obstacle factors,proposals were made to improve the quality of cultivated land in brown earth.The countermeasures were proposed,showing that the organic matter obstacle type region should firstly apply soil organic manure,implant the green manure,and return straw to field.The irrigation obstacle type region should take advantage of precipitation irrigation,construct anti-seepage district and support drip irrigation facilities to complement water saving irrigation system and improve the effective utilization of irrigation.The soil texture obstacle type region with sandy soil or clayey soil could use the methods of replace with out-soil,improving soil structure and irrigation by flooding to improve soil texture.