The quantitative impacts of drought and flood on crop yields and production in China

The disturbance of food production and the reduction of crop yields were observed due to droughts and flood locally and globally in recent decades. Previous studies used crop models to simulate the response of crop yields to some indices of extreme weather. However, most of these studies did not detect the impacts of droughts and floods quantitatively. In this paper, the statistical data of sown area (SA), covered area (CA) and affected area (AA) during 1982-2012, and crop yields and production of maize, rice, wheat and soybean in China during 1979-2015 in provincial level were collected. Using these data, we counted the occurrence frequency of droughts and floods. In different major grain producing areas (MGPA) of China, the superposed epoch analysis (SEA) method was applied to detect the quantitative impacts of droughts and floods on the crop yields and production during different periods (1982-1997, 1998-2012). The results presented that main crops had a 4.4%-6.8% yield and production reduction due to flood, and wider impacts on production and yield of main crops due to droughts were observed., with decreases ranging from 3.7% to 9.2%. Maize and soybean were more sensitive to drought in the whole China, especially in the NEC, with the significant reduction of 10.4%47.2% in the NEC and 6.4%-9.2% in the whole China. In China, both droughts and floods affected wheat yield with significant decreases of 4.3% and 6.1%, respectively. Moreover, different types of rice had various responses to droughts and floods. Early rice was sensitive to floods in China and in the mid-lower reaches of the Yangtze River (MLYR), but middle-season rice seemed to be sensitive to both droughts and flood in China. Meanwhile, crops responses during different periods varied, but did not have great difference of reduction between two periods. The spatio-temporal identification of quantitative impacts of drought and flood on crop yields and production in China is essential for applying suitable adoptions, such as better irrigation and basic construction in cropland to decrease the negative effects of droughts and floods on crops to guarantee the food security in China.