[Cotton water requirement character during recent 30 years in China.]

Variation of precipitation in the whole growing period and water requirement of cotton under different levels of annual precipitation assurance from 1981 to 2010 were analyzed based on precipitation data during the whole growing period and each growing stage. The results indicated that the China's precipitation distribution over the whole growing period, in general, was stable but decreased from south to north, and so was the distribution of water requirement, although it was higher in Xinjiang region. The precipitation deficit existed around the 35° N area, the maximum value was about 1000 mm, and the maximum surplus value was between 800 and 1200 mm. The water requirement declined during each growing stage, especially at flowering and boll opening stage, while the Kendall tendency varied from -3.6673 to -0.3733 in the whole growing period of cotton.