Comprehensive research on the state of agricultural drought in five main grain producing areas in China

Affected by climate change, drought disaster has intensified in China in recent years and it has become a major threat to national food security. The comprehensive evaluation and analysis of the agricultural drought state could contribute to the efforts to clearly grasp the extent and spatial difference of agricultural drought. It could also form the foundation to further strengthen drought management and improve drought resistance in China and elsewhere. To comprehensively evaluate the state of agricultural drought in five major grain producing areas in China, this study put forward a comprehensive crop drought index and the calculation method. The comprehensive crop drought index reflects both the overall area of a region affected by agricultural drought and the difference in the extent of comprehensive agricultural drought under the influence of different levels of drought. Five main grain producing areas were selected for the study, which were Sanjiang Plain, Songnen Plain, Huang-Huai-Hai Plain, Yangtze River Middle Plain and Jianghuai Plain, Sichuan Basin. In the first step, the water-sensitive stages during the growth period were determined in relation to crop phenological data. Then based on national daily meteorological data for 1982-2011 and the spatial distribution data for major crops in the region, the crop aridity index during sensitive stages was calculated along with comprehensive crop drought index. Next, the crop drought level was analyzed along with the state of comprehensive agricultural drought in the study area. The results showed that the states of comprehensive agricultural drought in Sanjiang Plain and Songnen Plain were more serious and the degree of drought in Songnen Plain was more significant. The degree of drought during spring wheat, maize and rice in the two areas was also non-negligible. Also the extent of droughts during spring wheat in Sanjiang Plain and during spring wheat, maize and rice in Songnen Plain were clearly noticeable. The state of drought in Huang-Huai-Hai Plain was the worst in the five investigated areas, especially the drought extent during winter wheat growing season. And extent of maize drought was also obvious and that of single-season rice was relatively small. The state of comprehensive agricultural drought in Yangzi River Middle Plain and Jianghuai Plain was mild. Early rice, late rice and winter wheat showed varying degrees of drought, and were given priority as moderate and lower- degree droughts. The extent of drought for late rice in Yangtze River Middle Plain and Jianghuai Plain was the most obvious. The state of comprehensive agricultural drought in Sichuan Basin was the lowest of the five studied areas. In the area, the degree of droughts for single-season rice and maize was lower while that for winter wheat was somehow more serious.