| The quality of cultivated land is the basis of increasing comprehensive agricultural productivity. Comprehensive mastery of cultivated land quality condition and research of quantity and special distribution of different lands can provide scientific basis and supports for rational distribution of agricultural production and cultivated land quality and production improvement. Wanzhou is located at the center of the Three Gorges Reservoir Region which is a special social economic region established along with the building of Three Gorges Project as well as the ecology development zone in Chongqing and plays the role of ecological protective screen. Setting Wanzhou of the Three Gorges Reservoir Region as the study object, through on-the-spot exploration, research and collection of latest statistics of Wanzhou land parcel change and social economy, by GIS technology, basing on present land-use map, soil map, slope map, topographic map and administrative map, the paper conducted overlay analysis, spatial interpolation analysis on Wanzhou district and acquired the quality score of cultivated land and basic evaluation unit. Combining with the evaluation factors of actual situation and social economic development level of cultivated land in Wanzhou, it can determine the weight and establish scientific evaluation system through analytic hierarchy process, entropy weight method, information amount weight method, etc. Through grading by utilization of multiple data quantitative model calculation and natural breakpoint method under 3S technology, it analyzed the quantity characteristics and spatial distribution pattern of studying cultivated land quality. Following are the significant results:1. The overall soil nutrients of arable soil in Wanzhou District are above average. The total nitrogen content is 0.13 g·kg-1~ 2.33 g·kg-1, of which 0.75 g·kg-1 ~ 1.50 g·kg-1 accounts for 69.85%; available phosphorus content is 2.0 mg·kg-1~ 74.2 g·kg-1, of which 5.0 mg·kg-1~20.0 mg·kg-1 accounts for 55.11%; rapidly available potassium content is 35 mg·kg-1~234 mg·kg-1, of which 50 mg·kg-1 ~ 100 mg·kg-1 accounts for 60.39%.2. Cultivated land quality is closely related to the soil type, geomorphic type, vegetation and economic factors. The synthetic score of quality of cultivated land in Wanzhou is 65.14~94.48, among which medium and low-yield field takes a large proportion. In quantity, medium quality cultivated land holds 81.2% of total cultivated area of Wanzhou, low quality and high quality hold 11.88% and 6.92% respectively. The annual output value and grading indicate that the grading result is well identical with actual output.3. The spatial pattern of cultivated land has demonstrated obvious regularities of distribution: firstly, along with the rising of land quality, the geomorphic type varies from southern part low mount deep hill trough valley – mountainous trough valley platform and piedmont deep hill – middle-lower part of low and middle mountains – middle and lower part of terrace and hills – low mount hilly area and platform area along sides of rivers – shallow hill and river valleys in middle part; secondly, the soil type varies from yellow soil and sand flat to paddy soil and purple soil; thirdly, the gradient is descending gradually; fourthly, the organic content, effective soil layer thickness, irrigation and drainage capacity, cultivation convenience of soil also have large impacts on it. In addition, land quality of each administrative division- villages and towns also demonstrate relatively obvious differences on spatial distribution.4. Utilizing the spatial autocorrelation measurement, and conducting quantitatively analysis on the spatial pattern of cultivated land quality of study area from the aspects of overall autocorrelation and partial autocorrelation, the land quality of Moran’sl value(0.47, p<0.05) indicates that the area has remarkable spatial agglomeration, and LISA spatial clustering figure directly reflects two closely correlated areas of middle part high value accumulation area and west and east low value accumulation area. The characteristic of spatial agglomeration and north and south differentiation is: high standard farmland division can provide technical improvement, which preferentially protects the high quality land source and makes improvements for concentrated low quality lands. It also provides evidence and reference for reasonable division of basic farmland preservation areas and reservation areas, scientific utilization of land sources and adjustment of planting industry structure.5. Mountainous region and hills take a large part of this area with a proportion of above 95%, with a few plains, dam fields and downlands among them. Generally it’s a region of multiple geomorphic types, complicated geological condition, slope farmland widely distributed and piecemeal land parcels, whose ecology condition is innately vulnerable. Aiming at the problems of cultivated land quantity, quality and spatial distribution, this paper proposed some reasonable suggestions from the strengthening of high quality farmland building, efficient rotation, land formation, scientific fertilization, crop planting according to circumstances, etc. Through the grading and evaluation of cultivated land, it can provide effective, targeted, operational techniques and methods for strict protection of lands. This does not only improve the land quality service of Wanzhou district, but also provide supports and references for adjustment of the soil source optimization and utilization model of the Three Gorges Reservoir Region.To protect the limited high quality cultivated land of the Three Gorges Reservoir Region, improve the general land quality level of this area and give play to the function of ecological protection screen of the Three Gorges Reservoir Region, basing on this study, it still needs to combine water and soil conservation, small watershed protecting ecological protection forest, etc., to thoroughly solve and coordinate the contradiction between the development and protection of the reservoir region. |
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