| Food security is an important part of national security, food security can not be separated from the "cultivated land", the cultivated land is important resource for human survival and development. China’s per capita amount of cultivated land is small, the overall quality of cultivated land is low, and the problem of land ecological destruction is serious, the reserve of cultivated land is insufficient, all these constitute great threat the food security. With the development of economy, society, increase of population, improvement of living standards, the demand for food has increased year by year, and the demand for construction land is also growing, tension of cultivated land resource was exacerbated by these. There are many factors that affect the food production, such as policy and system, investment, climate change and land condition, but change in the quantity and quality of cultivated land affects the grain yield directly, so it is a feasible and effective way to maintain food security in the context of insufficient reserve arable land resource, dwindling number of arable land. It’s helpful to land management by studying the the coupling mechanism between cultivated land quality and grain yield, and analysising of the driving mechanism of cultivated land quality factor on grain yield.Wansheng is the new urban development area of Chongqing, with a goal of proceeding with the new industrialization, informatization, urbanization and agricultural modernization, but 95 percent of the development space will still be agricultural space and ecological space in the future. At the same time, Wansheng is also a resource exhausted city, nurturing the development of modern agriculture is conducive to its economic transformation of Wansheng. Middle-low mountains and hilly areas are the dominant terrain of Wansheng, lacking high quality arable land. How to improve the quality of cultivated land and ensure food safety are major issue for the development of Wansheng. This paper selects Wansheng as the study area, with the period of 2009-2013 year, exploring the influence mechanism of 8 factors on Grain Yield on the foundation of analysising the variations of the quantity and quality of cultivated land. In order to provide theory reference and suggestions for the rectification work of Wansheng and other similar areas.The main research contents and conclusions of this study are as follows:(1) This paper reviews the progress of the research of cultivated land quality evaluation, accounts the capacity of arable land production, coupling of these two aspects at home and abroad, basing on the analysising of the concept of quality of cultivated land, quality gradation, land quality evaluation. To provide theoretical reference to this research.(2) Exploring the change of the quantity and quality of cultivated land in Wansheng on the basis of revealing the natural conditions, economic and social conditions of Wansheng, pointing out the characteristics and problems of land use from 2009 to 2013. This paper finds out cultivated land area of Wansheng presents a downward trend from 2009 to 2013 overall, change in different towns are not same. Arrangement sequence of relative change rate of cultivated land: Heishan town> Jinqiao Town >Guanba town>Conglin town > Shilin Town >Qingnian Town > Wandong Town > Nantong town; The main transfer direction is construction land, especially urban land, by analysising the transfer matrix of cultivated land from 2009 to 2013. Regional landscape pattern has an important influence on regional agricultural ecological system structure and function, the paper calculates four types of landscape index, includes the number of patches, mean patch area, area weighted mean fractal dimension, area weighted shape index, in order to reveal the change of farmland landscape pattern.It turns out that the number of farmland patch shows a gradually increasing trend from 2009 to 2013, average patch area shows a opposite situation, area weighted mean shape index AWMSI within a range of 21.3 to 21.6, AWMPFD distributes from 1.3 to 1.34, all the changes are relatively small, showing a downward trend, which shows that interference of farmland landscape pattern in Wansheng from human activity increases obviously, land fragmentation and land patch shape tends to rule are happening at the same time.In order to make full use of the existing cultivated land quality evaluation results, and make the research more significant for the work of land management, this research collects the results of evaluation of cultivated land quality Wansheng has, data of land consolidation project and land sampling, evaluates the quality of cultivated land of 2013, according to Regulations of Farmland Grading(GB/T 28407-2012). Comparing of 2009, 2011 and 2013, it turns out the arable land quality of Wansheng farmland classification is generally low, but the quality has been improved overall.(3) This paper analysising the changes of grain yield in Wansheng from 2009 to 2013 by the four indexes of total grain yield, grain yield per unit, per capita grain yield and grain production concentration degree. This paper accounts grain output of the theoretical yield and grain yield can be realized by establishing of the function relationship between standard grain theoretical yield and the natural quality of index, standard food can be realized and the utilization index, basing on the achievements of agricultural land classification. It turns out that the theoretical grain production capacity of cultivated land is 13.0939 ten thousand tons, theoretical yield is 8965.04 kg/hm2, while the grain production capacity can be achieved is 9.2753 ten thousand tons, the yield per unit area is 6350.55 kg/hm2. There is no correlation between grain yield and grain yield in Wansheng through analysising the spatial autocorrelation between grain yield data.(4) To analyze the influence of single factor on grain yield, establishing the corresponding relationship between factor levels and average values of grain yield, after classifying these factors in accordance with the order. Getting output levels corresponding to the index value of factors classification. According to the difference between the upper and the lower level of the factor index, we can calculate the output lifting space of each index. Results shows that improvement of effective thickness of soil layer is the most significant to grain yield, when it upgrade to the 60-70 cm from 40-60 cm, the amount is 774 kg/hm2. Followed by the terrace.When sloping terraces raised to level terrace, the grain yield increase reached 673 kg/hm2; altitude height has minimum increase effect on grain yield when it reduces to 1000-1500 m from more than 1500 meters. The figure is 60 kg/hm2, the upgrade is not obvious; followed by soil organic matter content increasing to 0.6%-1.0% from below 0.6% and sea level height decreasing to 750-1000 m from 1000-1500 m, the grain yield increment is 80 kg/hm2. Land natural quality points increase 0.1, the grain yield increased by 262 kg/hm2. Grain output will have an indirect effect on cultivated land. Calculating the Labor-Farmland Elastic Coefficient of Wansheng, it turns out that Wanshen belongs to the growth area. Therefore, Wansheng should take policy of increasing the land per labor cultivated, promoting scale management, improving the efficiency of agricultural production... |
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