Study On Temporo-spatial Variability Of The Grain Productivity Of Cultivated Land In Jiangsu Province

Land is fundamental factor in agricultural production and can not be replaced, Cultivated land, which is the essence of land, is the lifeblood of human living. As a core function, the productive capacity of cultivated land is the important cornerstone of grain security. With the development of economics and society in China, and the increasing of population, cultivated land has been continuously occupying. According to the UN Population Division predicts, China's population will reach 1.45 billion by 2030, which is the peak of Chinese population growth. On this situation, how to ensure grain security has become an unavoidable issue. Although many experts have different views on Chinese grain security, but in China, there has been a number of risks which threaten the grain security. "Hunger breeds discontentment", as a country with such a large population and farmland deficiency, the problem of grain security should never be ignored. Therefore, the systematic study of the key issues, for example, the reality productive capacity of cultivated land, what are the constraints to achieve the potential goal, is very important for us to understand grain security and protect the cultivated land.Based on the above background, supported by the projects of "Cultivated Land Classification in Jiangsu Province", "Estimating of Cultivated Land Productivity in Jiangsu Province", and regards Land assessment study and Geography as guides, the author choose cultivated land productivity as the base of the research, and summarize domestic and overseas research progress on land productivity evaluation, spatial and temporal variability of the grain productivity, and the research on agricultural regionalization, making full use of the technologies of GIS and RS. In this paper, the author firstly do the systematic research on the spatial and temporal variability of the grain productivity of cultivated land in Jiangsu province, and then propose a new calculation method and model of cultivated land productivity. At the same time, based on three different index—grain productivity of cultivated land, the potential productive capacity and the instability and volatility of grain production, the author also regionalize the farmland in Jiangsu Province. Based on research thinking'Yield-Capacity-Potential-Change-Zoning', this paper studies the temporo-spatial variability of the grain productivity of cultivated land and regionalization of cultivated land in Jiangsu Province. "Yield" means the reality grain production, "Capacity" means grain productive capacity, "Potential" refers to the potential productive capacity, "Change" refers to the instability and volatility of grain production, "Zone" means the management zones of cultivated land productivity. Four conclusions are drawn as follows:(1) Using the methods of GIS and Geostatistical Analyst, the author analyzed temporo-spatial variability rules and impact factors for farmland productivity in every county of Jiangsu Province, and we find out that, Over the past decade, the changes in grain production could be divided into two stages. In the first stage from 2000 to 2003, the grain yield in southern Jiangsu increased slightly, but in middle and northern Jiangsu the grain yield declined. In this stage, the total grain production in most of the regions had declined, limited number of county achieved only a small amount of growth. In the second stage from 2003 to 2009, the grain yield and total production in southern Jiangsu continuously declined, however in middle and northern Jiangsu above two indexes increased continuously. With change of the grain yield and total production, the advantages of grain production gradually decreased in southern Jiangsu which is the traditional cultivated production area, and the grain production in middle and northern Jiangsu gradually increased, and the core of grain production in Jiangsu Province has shifted from southern part to northern part. Over the past decade, the temporo-spatial variation characteristics of annual precipitation, mean annual temperatures and active accumulated temperature of ?10? have significant correlation with the temporo-spatial variation characteristic of grain yield per unit area, This situation indicats that precipitation and temperature are the controlling factors for the temporo-spatial variation characteristics of grain yield per unit area in Jiangsu Province.(2) The calculation of grain yield capacity can be broken down into three parts:the yield of natural quality of farmland, the impact by climate factors, the effect of human activity. Combined with RS and GIS technology, using the methods of mathematical statistics, we built a calculation model of grain yield per unit area of farmland yield capacity in Jiangsu Province, then based on this study, we calculate the cultivated land production and evaluated the temporo-spatial variation of grain yield per unit area. The results proved that, Jiangsu province had a overall high level of grain production, and the yield of grain production could be divided into five grades. Among them, the third grade distributed most widely, and the distribution of best—the first grade was the least, the whole showed a normal distribution. Based on the spatial autocorrelation analysis, landscape pattern analysis and statistical analysis, we found that the grain yield production was significantly correlated with the distance, especially in the southern Jiangsu and LianYunGang, HuaiAn, YanCheng in northern Jiangsu. From the perspective of cultivated areas, landscape patterns of grain production between different cultivated areas were disparate. If the order of Taihu plain area, Coastal plain area, Lixia-River plain area, Along-river plain area, Ning-Zhen-Yang hilly area, Xuhuai plain area were classified, the concentration of farmland yield production gradually decreased, the dominant grades of yield production gradually increased from one or two kinds of grades to all five grades. The Geostatistical analysis indicated that the trend of grain yield per unit area was gradually decreasing from south to north in Jiangsu Province, but the surrounding areas of Taihu lake in southern Jiangsu was still the most favorable regions for grain yield production. The total production level of grain production in Jiangsu was divided by the Yangtze River as the boundary, the areas of southern Yangtze River were low, and except a few prefecture level cities, the rest areas in northern Yangtze River had higher total grain production.(3) Using the methods of ESDA and mathematical statistics, the temporo-spatial variability rules and impact factors of achieved level of productive capacity were analysed The results showed that:In Jiangsu province, the place with higher using intensity of the grain yield production were mainly distributed in middle and northern Jiangsu, most place with higher using potentiality were distributed in southern Jiangsu. Overall, most place were at lower level of using intensity of the total grain production. The place with higher using intensity were all distributed in middle and northern Jiangsu. The place in southern Jiangsu were at the lower level. The use potentiality of total grain production was generally higher, the northern Jiangsu was highest, followed by southern Jiangsu, and the middle Jiangsu was lowest. In different socio-economic development conditions, impacted by the comparative benefit of crop and cultivated policies, soil fertility, soil quality and crop management showed the corresponding differences, all of these together with the differences of climate conditions, formed the spatial differences of grain yield using intensity in Jiangsu. The condition of using intensity and grain yield productive capacity determined the differences of yield potential. Total production intensity was mainly affected by the yield using intensity and cropping index, and total production potential was mainly determined by cropping index and farmland area, of which the farmland area had more impact.(4) Through analyzing the changes of grain production capacity and its uncertainty of cultivated land by using the GIS spatial analysis method and considering the indexes of the total grain production capacity, the realizable level of the total grain production capacity, and the proportions of primary industry in GDP around Jiangsu Provence, we do management zoning for the grain production of cultivated land in Jiangsu Provence. The results indicate that:all the counties of Jiangsu province can be divided into three Level 1 divisions—Protection Zone (zone ?), Promotion Zone (zone ?) and Optimized Using Zone (zone ?). The zone ? had the highest total production capacity, and the proportion of primary industry was more than 20%, this kind zone will become the important protection zone for grain production. The zone ? had the greatest area among the three types of zones, the proportion of primary industry is between 10% to 20% in GDP, the kind of zone should strengthen development use and increase utilization, to achieve a larger increase of grain production, which can provide important support for grain security. The zone ? had the highest grain yield, while the area of farmland in this zone was the least, the total productive capacity is the lowest in Jiangsu, and the proportion of primary industry in GDP was less than 5%. In the future, we need to further restrict to converse the farmland into construction land, try our best to protect the quality farmland which has been relatively scarce.Based on the combination type of "Potential-Change" of grain productive capacity, the above three kinds of zones could be further divided the sub-zones, Zone ? can be divided into four sub-zone, zone ? into four sub-zones, and zone ? into three sub-zones.