Abstract: In order to study theoretical potential productivity, yield promotion space, yield constraints and the solution approaches,we used AEZ (Agricultural Ecology Zone) model to estimate the photothermal potential productivity of rice and calculate the rice yield gaps from 1980 to 2010 in southern China. The results showed that early rice potential productivity continued to increase with grater increasing rate than the actual yield, so the early rice yield gap became bigger. The potential productivity of medium rice and late rice was declined; and the rice yield gap became smaller. The analysis of climatic factors showed that temperature and radiation in rice growth period were the most important impact factors for rice potential yield and yield gaps. The positive effect of temperature increasing for the early rice was bigger than the negative effect of radiation declining, resulting in the increase of the potential productivity. On the contrary, the negative effect of radiation declining for medium rice and late rice was bigger, so the potential productivity was dropping. The temperature and radiation in rice growth period were different, causing different changing trends of rice potential yield and yield gap between provinces.

Key words: Southern China, Rice, Yield gap, Photothermal potential productivity, Climatic factors