| Cultivated land is the basis of agricultural production and social stability,and it is of great significance to the sustainable development of society.Health of cultivated land is related to national food security,ecological environment quality,social stability and even national political power.Therefore,scientific evaluation of cultivated land quality is the premise to ensure food security and improve the quality of cultivated land,and it is of great significance to the coordinated and sustainable development of cultivated land and ecological environment At present,the evaluation method of cultivated land quality mainly consists of constructing of evaluation index system,calculating the evaluation index value and choosing the evaluation method.In the selection of evaluation indexes of cultivated land quality,researchers usually focus on cultivated land fertility level and management conditions,while pay less attention to soil pollution,ecological environment,and cultivated land health.Meanwhile,due to the influence of plasticity area unit,the accuracy of evaluation results is limited in the process of cultivated land evaluation.In order to improve the evaluation of cultivated land quality,the following research work was taken,using Xiangzhou district,humpy ground in northern hubei as the research object.1.In reference to the cultivated land quality level,the soil environment quality standard,and land quality geochemical assessment procedures,combined with consideration on human health,environmental protection and sustainable demand,five types of indexes relating to physical and chemical properties,nutrient condition,ecological environment,management conditions and physical condition were chosen for first level indicators for cultivated land quality evaluation.Then,28 indexes including terrain area,soil organic matter,rapidly-available potassium,effective phosphorus,sulfur,boron,effective,effective cadmium,soil nitrogen runoff,soil phosphorus runoff and so on were chosen for secondary level of indexes,constructing the evaluation system including cultivated land basic condition dimension,cultivated land health condition dimension and cultivated land ecological environment dimension.Using analytic hierarchy process(AHP),Delphi method established the evaluation model to determine the weight and value of the evaluation index.According to the data of sampling points in the research area,the index of each dimension was calculated,and the grade of each dimension was determined by the grade-by-grade correction method.2.The cultivated land map spot in the second national land survey database was used as a small scale cultivated land quality evaluation unit On the basis of this evaluation unit,a large scale evaluation unit was constructed by combining the map spot with the same administrative region,the same grade of slope,the same type of cultivated land,and the adjacent plots in pairs.Interpolation and verification points were selected by random sampling method,and interpolation analysis was carried out in size scale evaluation unit by using inverse distance weighting method(IDW),Spline interpolation method(OK)and ordinary kriging method(OK)respectively.The evaluation data of each evaluation unit were obtained.After comparing the root mean square error(RMSE),average error(ME)and imprecision(IP)of several combination interpolation results and verification point position data,it is found that the evaluation accuracy of IDW method combined with small-scale evaluation unit is slightly higher than that of other combinations.Therefore,in the evaluation method of cultivated land quality in Xiangzhou district,the inverse distance weight method and the small-scaled evaluation unit were selected in this research.3.Using the evaluation model with the sampling data by inverse distance weighting method on a small-scaled evaluation unit in this research,each dimension of evaluation index including the cultivated land basic condition,cultivated land health condition,the cultivated land ecological environment and the cultivated land quality grade level was analyzed and displayed on distributions under different types and different regions.The average grade of cultivated land basic condition in Xiangzhou district is 5.48,with the fourth,fifth and sixth grade as the main grades.The cultivated land area of the three grades is 131,812.94 hectares,accounting for 79.74%of the total.Cultivated land with higher grade of basic condition is mainly distributed in Shuanggou,Zhangjiaji and Guyi towns.The average grade of cultivated land health in Xiangzhou district is 6.24,with fifth,sixth,seventh and eighth grade as the main grades.The cultivated land area of the four grades is 149,402 hectares,accounting for 90.38%of the total cultivated land area.The cultivated land with higher health status is mainly distributed in Shiqiao,Huanglong and other towns.The average grade of cultivated land ecological environment in Xiangzhou district is 3.12,with the second,third and fourth grade as the main grades.The cultivated land area of the three grades is 154363.27 hectares,accounting for 93.38%of the total cultivated land area.Cultivated land with higher grade of ecological environment is mainly distributed in towns and villages such as Huopai,Guyi,Huanglong and Yushan towns.The average grade of cultivated land quality in Xiangzhou district is 6.09,with fifth,sixth and seventh grade as the main grades.The cultivated land area of the three grades is 126,990.23 hectares,accounting for 76.82%of the total cultivated land area.The cultivated land with higher quality is mainly distributed in Huanglong,Yushan,Shiqiao,Guyi and other towns.4.Comparing with the results based on the evaluation index system of the cultivated land quality and grade,the cultivated land quality grades of different villages and towns spanned significantly greater for the results from the evaluation methods used in this research.Moreover,the evaluation results in this research had more administrative levels,and were more sensitive to the response of the evaluation index.At the same time,since the evaluation model was set with different dimensions and the selection of indicators was more abundant,evaluation results can reflect more on cultivated land conditions from the aspects of nutrient,ecological environment and health status.We believe that it will be more favorable for the detection of problems and the finding of solutions on cultivated land quality.5.Index ranks were built for each evaluation index based on the distribution of heat maps.Based on that,the limiting factors of the level of each dimension were explored combined with the level of each evaluation index connotation.The results showed that the main limiting factors of cultivated land quality in Xiangzhou area included soil bulk density,organic matter,total nitrogen,effective phosphorus,pH,effective sulfur,effective boron,degree of forest network of farmland and soil runoff nitrogen and phosphorus,etc.According to these limiting factors,the countermeasures and suggestions for the improvement of cultivated land quality were put forward.In all words,evaluation indexes of cultivated land were selected from the aspects of physical and chemical properties,nutrient status,health of cultivated land and ecological environment to reflect the status of cultivated land in a multi-dimensional manner in this research.Different interpolation methods were used on evaluation units of different scales.And the appropriate interpolation methods and evaluation units were selected to improve the evaluation accuracy.Then the present situation of cultivated land in Xiangzhou district of the research area was comprehensively displayed.And then the limitation factors of cultivated land quality were found based on the evaluation results.Finally,suggestions were provided for cultivated land improvement and environmental protection. |
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