Study On Evaluation Of Paddy Field Productivity In Hilly Area

China has a large population,but there is an obvious contradiction between people and land, and the issue of food security becomes serious.Land especially arable land is the basis resources of human survival.A reasonable assessment of the quality of arable land is quite important for the rational use of land resources and the prevention of land degradation.Meanwhile,the issue of land degradation and decline of soil fertility is also rigorous.To improve the quality of arable land to make rational use of land,it's necessary to Evaluate of soil fertility of arable land and find out the impact factors of soil fertility and changes.Therefore,we need to carry out a new grip on the land survey and evaluation.In this paper,we selected paddy fields of He chuan as the study area because of its typical hilly landscape.By the support of GIS(geographic information systems) and computer technology,we use Delphi method to select 10 factors as soil fertility evaluation factors,and also we use AHP (Analytic Hierarchy Process) to determine structure matrix and to determine the weight of each factor.According to the characteristics of the various factors and their impacts on soil fertility,we used fuzzy mathematics method to build a membership function.As to the construction of the database,we used GIS technology to complete.We calculated the model index in soil fertility between 0.505 and 0.845 based on the grid - vector mixed data.Then we used mean values method to calcify the arable land,meanwhile we produced thematic maps of soil fertility.The main results were as follows:(1) Soil organic matter,nitrogen,available phosphorus and potassium of Hechuan were in line with the approximate normal distribution,and their interpolation can be calculated.This study used statistical methods to study the spatial variability of the main nutrients of this study regional,and used GIS software to produce maps of spatial variability,results showed that:①OM,N,P and K expressed the moderate spatial variability,which was cased by a common structural and random factors,and the size of its coefficient of variation expressed as:K＞N＞P＞OM;②they expressed a good semi-variance structure,which showed that in regional scale there was a range of spatial correlation of the content of soil OM and available N,P and K;③the greater the coefficient of determination R~2,the better model goodness of fit,and taking into account the coefficient of determination R~2,the level of the best fitting was the nitrogen;but available phosphorus was with the worst model fitting.Based on the study of the frequency distribution and the spatial distribution of soil nutrient nutrients content,and according to the classification of soil nutrient standards of the integrated system of soil nutrient assessment(Table 4-4),this paper primarily estimated soil nutrient condition,and results showed that:soil organic matter content of study region in all grades was in a low range of the study area,which indicated a serious lack of organic matter;the content of nitrogen was mainly distributed in the framework of four grade,and only a small number of samples tested were in the below of threshold value,which indicated the content of nitrogen was in a ordinaly level; available phosphorus content was in a relatively more dispersed,but most of that was in a critical value,which indicated available phosphorus content of the study area was sorely lacking;and available potassium content was mainly distributed in the framework of six levels with more diffuse distribution,and each kind of rating points was more or less the same,but most of that was in a critical value,which indicated available potassium content of the study area was sorely lacking.In general,soil nutrient content was generally low in Hechuan,and there was a certain difference in the situation of soil nutrient content among different land type.(2) According to composite index of arable land fertility of the evaluation unit Hechuan,soil fertility is divided into six levels using the average method.And we draw thematic maps by ArcMAP9.0 and counted the areas of each level.Among these levels,the area of the first level was 2240.5hm~2,accounting for total area of arable land 4.94%;the second was 24140.6hm~2,accounting for 53.25%;the third was 15099.7hm~2,accounting for 33.31%;the fourth was3242.2hm~2,accounting for 7.15 percent;the fifth was 298.1hm~2,accounting for 1.32%;the third was 12.2 hm~2,accounting for 0.03%.The classification objectively reflected the reality.And according with the actual situation in each level,we sumed up a set of suitable measures to improvement the fertility.In this paper,we developed an effective methods and technical processes to carry out the investigation and evaluation of soil fertility of arable land in a hilly or mountainous area.This was also an event of great significance to the management and sustainable use of cultivated land resources,as well as to the soil survey and land evaluation which was now being carried out by the Ministry of Agriculture.