Comparison between the potential grain productivity and the actual grain yield of cultivated lands in mainland China

chinois. 通过耕地粮食生产能力与粮食现实产量的对比，分析耕地的粮食增产潜力及其省际差异。以105个农业生态小区为研究单元，在确定能够充分发挥当地气候资源潜力的种植制度的基础上，根据粮食作物审定品种的区域试验产量，计算了各区域各个耕地亚类的粮食单产能力；再分别乘以各县2004年相应耕地亚类的面积，得到2004年各县的耕地粮食总生产能力，进而汇总出各省以及全国的耕地粮食总生产能力；结合近3年（2002～2004年）的粮食现实产量，分析耕地的粮食增产潜力、粮食生产能力开发程度及其省际差异。2004年全国耕地粮食总生产能力为9.20亿t，远高于全国近3年4.52亿t的粮食平均产量，目前粮食安全的耕地资源保障程度较高。从各省的计算结果来看，除新疆以外，单位耕地的生产能力和增产潜力均表现出从东南向西北递减的趋势，其中内蒙古、宁夏、甘肃、青海、西藏5个从东北向西南延伸的省区最低；位于中国广大北部、西南部的省市，受土壤质量、灌溉条件的限制，粮食生产能力的开发程度低，粮食生产虽有一定增产空间，但实施难度较大或需大量投入。保障粮食安全首先要抓好中国农业生产基础较好的东部、中部地区的粮食生产；同时也要加大广大北部、西南部地区的农业基础设施投入，积极开展土地整理、中低产田改造，进一步开发这些地区的粮食生产能力。

anglais. The purpose of this paper is to explain the potential of increasing grain production in each province and to explain interprovincial differences by comparing the potential grain production and the actual grain yield of cultivated lands. First, cropping systems were determined for 105 agro-ecological regions, through which potential climatic productivity could be sufficiently developed. Based on the regional test yield of the certificated grain cultivars and cropping systems, the potential grain productivity of per unit area was calculated. The gross potential grain productivity in each county, province and Mainland China was obtained by multiplying the potential grain productivity of per unit area and the cultivated land area in 2004. By comparing it with the actual yield, the potential to increase grain production, the exploitation level of potential grain productivity and the differences between each province were acquired. The results show that the gross grain potential productivity in Mainland China was 0.92 billion ton in 2004 and that there was a large gap between the potential grain productivity and the actual yield, averaging 0.45 billion ton in recent three years. There is high assurance for grain security at present. From the results of each province, the average potential grain productivity of per unit area declines from the provinces in the southeast to those in the northwest of China, apart from Sinkiang, while that of Inner Mongolia, Ningxia, Gansu, Qinghai, Tibet, stretching from northeast to southwest of China, is lower than that of the others. The potential to increase production per unit area captured the same trend as the potential grain productivity per unit area, which indicates that the more potential grain productivity, the more potential to increase production for a province. The provinces lying in the north and southwest of China witness low level of potential grain productivity and exploitation because of the limitation of soil quality and irrigation conditions. These are the areas where soil is hard or needs too much investment to explore more potential grain productivity. As such, in order to ensure food security, food production in the east and middle of China, where basic agricultural bases are relative better, there should be more emphasis. In addition, basic agricultural infrastructure construction, land consolidation and the improvement of medium or low-yield cultivated lands should also be advocated in the north and southwest of China to explore the potential grain productivity.