Evaluation Of Cultivated Land Productivity In Liangping County

In China,the average cultivated land is limited for large population,and the contradictions between human and cultivated land are increasing severity.In order to make full use of farmland, strengthen effective management of cultivated land,realize population,resources,and environment sustainable development,we must clearly understand the basic situation of farmland.However,the second soil investigation have past more than 20 years,during this period,the cultivated land quality of our country and soil fertility status have changed greatly,so it is necessary to carry on a new and overall investigation and evaluation.Liangping County of Chongqing was selected as the study area in this paper.On the support of GIS and computer technologies,12 indicators were chosen to evaluate cultivated land productivity using the Delphi method,and then the weight of each factor was determined by AHP(Analytic Hierarchy Process).The paper set up membership functions in terms of their characteristics and different influence on the quality of cultivated land using fuzzy mathematics method.Based on GIS platforms,the database was constructed.Meanwhile,applying the grid-vector data and the fuzzy comprehensive evaluation model to get the integrated fertility index of cultivated land,and using the mean values method to classify the cultivated land,simultaneously to manufacture the grades map of cultivated land productivity.Moreover,in the hilly region,there were remarkable differences of planting and fertility application management between the paddy field and the dry land,which could result to the notable differences of the cultivated land productivity.Therefore,this research had evaluated the productivity of the paddy field and the dry land separately,and comparative analyzed its results to study their differences further.The main results obtained in this paper are summarized as follows:1.Spatial variability of soil nutrients.In the process of cultivated land productivity evaluation, this research analyzed the spatial variability of the main soil nutrients,which included organic matter, ammonium nitrogen(NH₄⁺-N),available Potassium(K)and phosphorus(P),and made their spatial distribution map using GIS technology,to understand the spatial distribution of each nutrient clearly.The result indicated that all studied soil nutrients presented moderate variability,and the variation coefficients showed in order of P＞N＞K＞OM(%).Theresults suggested that semi-variance structures for spatial variability of soil nutrient content existed in the study area.OM and N exhibited moderate spatial variability,which were caused by structure and random factors,however, P and K displayed weak spatial variability,which were mainly caused by the random factors. Moreover,the spatial distribution of soil nutrient content was different from each other,but there was also a certain similarity in some area.Organic matter showed higher content in eastern and western area,but lower in middle,southern and northern area;the available N showed higher in the plat area of middle,and lower in eastern,western and northern;the available P showed high homogeneity in the study site,only higher in few areas;however,the spatial distribution of available K was more complex than the other soil nutrients,and showed strong spatial non-uniformity characteristic.2.Evaluation of soil nutrient status.On the basis of frequency distribution and spatial distribution pattern of soil nutrient,the soil nutrient status was primarily evaluated according to the classification criterion of soil nutrient of ASI(Agro Services International).The results showed that soil nutrients content in LiangPing was lower in general and there were certain differences among the soil nutrient contents of different cultivated land types.3.Evaluation of Cultivated Land Productivity of Liangping.According to the integrated fertility index of all the evaluate units,cultivated land productivity in Liangping was classified into eight grades using the average value method.Evaluation theme maps of cultivated land productivity and statistics were carried out using ArcMAP9.0.The area and percentage of the first,second,third, fourth,fifth,sixth,seventh,and eighth grade were 62.3.7 km²,8.04%,70.40 km²,9.08%,92.50 km², 11.93%,133.00 km²,17.15%,139.84 km²,18.03%,115.07 km²,14.84%,97.45 km²,12.56%,and 64.97 km²,8.38%,respectively.However,there were some differences of soil fertility and cultivate system between dry land and paddy field in hilly area which caused to the different productivity of paddy field and dry land.In order to describe the cultivated land productivity exactly,it was necessary to separate the evaluation results of paddy field and dry land,and to draw the theme map of evaluation results respectively.4.The difference analysis for the productivity of the paddy field and the dry land.Statistical analysis based on the cultivated land productivity theme maps showed that there was remarkable difference between the productivity of paddy field and dry land.For the paddy land,the area of different grade showed in the order of the fifth grade land＞the fourth grade land＞the sixth grade land＞the third grade land＞the seventh grade land＞the first grade land＞the second grade land＞the eighth grade land.For the dry land,the area of different grade presented in the order of the fourth grade land＞the fifth grade land＞the sixth grade land＞the seventh grade land＞the third grade land＞the eighth grade land＞the second grade land＞the first grade land.5.The spatial distribution of cultivated land productivity.In view of the remarkable difference of productivity between paddy field and dry land,during the process of studying on spatial distribution of cultivated land productivity grades,statistical analysis was carried out on the evaluating result maps of paddy field and dry land,respectively.Then the region distribution and the administrative area distribution of different grades of paddy field and dry land could be obtained by overlaying correspondence maps. Finally,descriptive analysis of the attribute characteristics of different levels of dry land and paddy field,the existing problems of cultivated land use,and some suggestions of reasonable land uses and land improving were addressed in this study.An effective method and technical process in using GIS to develop the investigation and evaluation on cultivated land productivity in hilly area was put forward in this research.It had positive significance not only on the scientific management and sustainable utilization of farmland in the hilly area,but also on investigation and evaluation of cultivated land productivity project of the agriculture ministry.