Evaluation Of The Quantity Of The Cultivated Land And Calculation Of It's Safe Baseline

China is an agricultural country with large population, so, To fulfill the food demand of domestic market is a main issue of agricultural security. The cultivated land, which is the focus of agricultural secure issue, is most important resources of agriculture; moreover, the security of cultivated land's quantity takes a main part in security of cultivated land resource. With the fast growth of economy and population of our country, the situation of cultivated land resource is changes constantly, which leads to a contradiction between the development of economy and security of cultivated land resource. It has been highly emphasized by all respect.At present, domestic scholars have been researching initially on issues about cultivated land security, skimming over these researchers that were mostly emphasized on the concept of cultivated land security, content of researches and solutions of problems, while it was lack of classification of cultivated land security and quantitative analysis. This research used both qualitative analyses and quantitative analyses, the research proposed a bottom line of cultivated land resources to been utilized safely according to analyze security situation of regional cultivated land resource. This research is meaningful to arranging cultivated land resource harmoniously to economic development and food security, alleviating the contradiction between increased population and limited cultivated land resource and ensureing to use safely the land resource.Based on the different characteristic and regulations of the utilization of cultivated land of each County in Leshan city, The paper will use different ways to analyses the spatio—temporal change in utilization of cultivated land in Leshan city in the period of 1996—2005 .such as Changes in intensity index of cultivated land,annual changed quantity,the annual changed rate,the changed contribution rate of the utilization of cultivated land. Entropy empowered to use law combined with AHP. The paper se ts up indexs of assessing,and analyses the Status of cultivated land resources quantity security; At the same time, based on carring capacity of cultivated land, and also the quantity security cultivated of land resources is analysed, The GM (1, 1) and the time curve estimation will be applied to forecast future demand of calcuating safe baseline.(1)①There were four levels of the intensity indexs of the farmland usage: the Shizhong district and Shawang district are the fastest abating area. Jiajiang country is in the faster abating area. Qianwei country ,Jingyan country and Emei city are normal abating area. The value of the intensity index of the farmland exploitation in Shizhong district (0.8572) is 6 times as many as Muchuan country (0.1454).②The changing of intensity index of the farmland usage is fast, average degree of farmland usage is 2.4259%. The order of the dynamic degree of farmland usage is (form highest to lowest ) as follow:Shawan>Ebian>Shizhongdistrict>Jingkouhe>Emei>Jiajiang>Mabian>Jianwei>Jingyan>Muchuan> Wutongqiao. And the highest is 4.5585%, lowest is 0.5673%. And also,change rate and change annual rate (form highest to lowest) as follow:Shizhongdistrict>Emei>qianwei>Shawan>Jiajiang> Ebian>Jingyan> Muchuan>Jingkouhe>Mabian>Wutongqiao.The highest of change annual rate is 796.30 hm~2,and the lowest of ones is 79.2600 hm~2.③The average absolute contribution ratio of the intensity index of the farmland usage in Leshan is 9.0909, in all of the countries, Shizhong district has the highest absolute contribution ratio (17.0337), and the Wutongqiao has the lowest (1.6954). The contribution relative ratio is 1.1768. And Shawang district has the highest contribution relative ratio of the intensity index of the farmland usage, the value is 2.1914 and the Muchuan has the lowest one only 0.4432.(2) According to analysising the bearing capacity of farmland in Leishan from 1996-2005,the result shows that①the scale of grain production in Leshan cannot fit for the population, and the quantity of the farmland resources cannot meet the need of grain safety②At 95% and 90% of the grains self-sufficient ratio under the two programmes, In the recent years, the index of farmland pressure (K>1), this shows that the farmland resources is facing tremendous pressure.(3) .From 1998 to 2003, the comprehensive safety value of farmland quantity keeped reducing. And the condition of farmland resources became become more and more serious, the value of farmland quantity comprehensive safety in 2003 was 15.8512 and in 2005 the value was 16.8769.(4) The farmland resource will keep decreasing. The area of cultivited land will be decreased to 12.0103×10~4hm~2 under per capita demand of 400Kg grain in 2010. That will be 13.6846×10~4hm~2 under per capita demand of 420Kg grain in 2015. There is a gap between the cultivated land and the bottom line.(5) According to the characteristic of the development of area economic and the demand of sustainable development, It suggest that we should keep the quantity of the farmland, improve the quality of the farmland, protect the ecological environment, and intensify the management of land Strict implementation of cultivated land use,the use of economic levers of cultivated land resources utilization will regulate, draw up the genera] plan of land utilization, and the execution method countermeasure and the advice,so that we of controlling the speed changed of farmland . safeguard the quantity of the farmland and achive the sustainable utilization of land.