中国耕地和粮食生产力变化的省际差异研究

我国耕地面积自1957年以来持续减少。为了供养更多的人口、基本保证粮食自给，必须提高单位面积产量，并保持一定数量的耕地。根据50a来耕地面积、复种指数、粮食产量等统计资料，分析我国省际耕地面积和粮食生产力变化的差异，提出耕地粮食生产力相对指数的概念，定量分析各省耕地在全国粮食生产中的相对重要性，为耕地保护政策提供科学依据。建国以来我国的耕地和粮食产量变化具明显的省际差异，耕地变化的区域差异显示生产力较高的耕地在减少，生产力较低的耕地在增加。从东南向西北我国耕地粮食生产力逐渐下降，长江中下游地区耕地粮食生产力最高，这些省市耕地减少对粮食生产的影响更大，东南部耕地粮食生产力下降的主要是由于种粮的比较利益低下、耕地数量有限、人口稠密和复种指数下降等。

PROVINCIAL DIFFERENCE IN CULTIVATED LAND AND GRAIN PRODUCTIVITY IN CHINA

China's cultivated area has decreased steadily since 1957. In order to feed more and more people and to assure grain self-sufficiency in general, we have to improve yield of farm crops per hectare and keep certain area under cultivation. This paper has revealed the provincial difference, the quantity change of cultivated area and grain productivity change according to the data of long-series statistics of cultivated area, multiple cropping index, and grain yield during the past 50 years. This paper puts forward the conception of ratio of provincial's grain productivity to national average, and has quantitative analysis of the comparatively weightiness of cultivated land's grain productivity in every province, which is expected to provided scientific foundation for making-decision of protect cultivated land. There're obvious provincial difference in cultivated area and grain productivity change since the founding of New China. The regional difference of cultivated area change indicates higher productivity cultivated area decreases while lower productivity cultivated area increases. The cultivated area's grain productivity becomes small from south-east to north-west part in China. The highest cultivated area's grain productivity is located in the region of the middle and lower reaches of Yangtze River. Decrease of these provinces' cultivated land will exert greater influence. The driving forces for the decrease of cultivated land's grain productivity in south-east are lower comparative benefit, fewer cultivated land, denser population, and falling multiple cropping index.