Transformation And Convergence Of Different Cultivated Land Quality Evaluation Systems In Hubei Province

Agriculture is a basic industry closely related to politics and economy.Cultivated land is an important guarantee for agricultural production.Therefore,the evaluation of cultivated land is of great significance to the protection of cultivated land,food security and national stability.In 2008,China’s agricultural sector established an evaluation system of cultivated land fertility,deployed to carry out the work of cultivated land fertility evaluation;in 2017,the agricultural sector updated and improved the evaluation system,the work of grade evaluation of cultivated land quality has been deployed and carried out.However,there are some differences between the two evaluation systems in terms of evaluation purposes,index setting and weight determination,and the comparability of evaluation results is poor.It is therefore not possible to take full advantage of the gains made over the past decade or so,thus providing a reference for decision-making in the protection and management of cultivated land,it can be seen that the in-comparability of evaluation results greatly impedes the flow and interaction of data.Therefore,it is of great significance for the agricultural sector to promote the protection of cultivated land by constructing the linking models of different systems so as to realize the effective linking of the evaluation system.This research takes Hubei province as the research area,taking the two evaluation systems and evaluation results of cultivated land productivity and cultivated land quality grade as the research object.Firstly,compares and analyzes the similarities and differences of the two evaluation systems,the feasibility of linking up the evaluation results in theory and practice is demonstrated.Then,by introducing terrain,climate,human activities and other variables,different regression analysis methods are used to establish the joint model of the two evaluation results,from which the joint model with the highest accuracy is determined.Finally,the evaluation results of the same cultivated land evaluation system in different years after conversion are used to study the spatiotemporal evolution of cultivated land quality in Hubei province.The main findings are as follows:(1)There are not only similarities but also differences between the cultivated land productivity evaluation system and the cultivated land quality grade evaluation system.First,the evaluation aims are highly consistent and serve the important theme of protecting cultivated land.Secondly,in the evaluation system,the cultivated land quality grade evaluation system is superior to the evaluation system in the comparable range,evaluation precision and index rationality.Finally,there are interconnections in the evaluation methods,which follow the three basic principles of "from point to surface","fuzzy evaluation","progressive layer by layer".Although there are differences between the two evaluation systems,their evaluation aims and evaluation methods are relatively consistent.(2)Multivariate linear regression model,random forest regression and support vector machine regression model were used to link the two evaluation results.The results of the model training show that the fitting precision of the random forest regression model is higher than that of the other two regression models.Therefore,the random forest regression model is chosen as the joint model,and the cultivated land quality evaluation result in 2013 is calculated as the input value.The results obtained are comparable with the results of cultivated land quality grade evaluation in 2018.(3)The results show that from 2013 to 2018,the cultivated land quality in Hubei province has been upgraded from 5.28 to 4.79,and the cultivated land quality has been improved.In 2013,the area of medium grade cultivated land accounted for 41.74% of the total area of cultivated land in the province,and 66.70% in 2018.The proportion of medium grade cultivated land increased.In 2013,26.43% of the province’s total cultivated land area was of high-grade arable land,and in 2018,20.24% was of highgrade arable land.In 2018,the area of low-grade arable land accounted for 31.84% of the total area of arable land in the province,and in 2018,it accounted for 13.05%.(4)The results show that from 2013 to 2018,the area of cultivated land that cultivated land quality grade promotes is the biggest,the cultivated land grade reduces next,the cultivated land area that cultivated land quality maintains stable is the fewest.The area of cultivated land quality grade upgrading is 2849,838.39 hectares,accounting for 54.43% of the total area of cultivated land in the province.The area of cultivated land quality grade decreasing is 1508,301.56 hectares,accounting for only 28.81%,the cultivated land with stable quality grade was 877257.01 hectares,accounting for 16.76%.(5)In view of the improved quality of cultivated land,it is necessary to maintain the current production conditions of cultivated land,maintain the productivity of cultivated land by means of comprehensive management,and pay attention to the protection and improvement of soil fertility,push the quality level of cultivated land to a new level.In view of the steady and constant quality of cultivated land,on the one hand,the areas with poor quality of cultivated land should continue to carry out relevant policies to improve the quality of cultivated land.On the other hand,in areas with better quality of cultivated land,attention should be paid to maintaining the current farmland ecological environment and to combining land use with land conservation so as to maintain the cultivated land at a higher level.In order to improve the quality of cultivated land,it is necessary to find out the key factors which affect the improvement of the quality of cultivated land.