Analysis of spatial and temporal characteristics of water requirement of winter wheat in China

Crop water requirement (ETC) is the basis for farmland water management and irrigation.Based on the meteorological data from 356 stations of 22 provinces (cities, and autonomous regions) and the data of the growth period of the winter planting area in China, the water requirement (ETC) of winter wheat of the whole growing period and different growth stages during 1961-2010 in China were estimated by using FAO Penman-Monteith equation and crop coefficient method, and the spatial and temporal distribution characteristics of ETC were cleared. Combined with the spatial distribution characteristics of precipitation, the water-meeting situation of winter wheat during the growing season was analysed. Results revealed that the spatial distribution characteristics of precipitation of the whole growing period and different growth stages of winter wheat were all significant which were higher in the southeast coast areas and lower in the northwest areas except the growth stage of sowing to over wintering (emergence). Except during the growth stage of turning green (emergence) to jointing, the spatial distribution characteristics of ETC of the whole growing period and different growth stages of winter wheat were all significant, which were higher in the northwest and lower in the southeast. The ETC of winter wheat of the whole growing period and different growth stages were decreased over nearly the past 50 years, especially the whole growing period and the growth stage of flowering-to-ripening. The growth stage of turning green (emergence) to jointing decreased the slowest. From the national average angle, except for the regions of Huanan and the lower reaches of Yangtze River where the conditions of water-meeting were better, the precipitation of the whole growing period and different growth stages of winter wheat can not meet the demand of water in other regions, ignoring the irrigation conditions. Comparing the water-meeting of winter wheat of the typical stations of different regions, the water deficit is most serious in the winter wheat regions of the North, the Huanghuai, Xinjiang and the Southwest. By comparing the water deficit of the most serious areas, the growth stage of the water deficit of the least seriously is from sowing to over wintering and the growth stage of the water deficit of the most seriously is from flowering to ripening, which is the most important stage for the grain weight of winter wheat, So timely irrigation is very important if conditions permit, which is the key to ensure a high and stable yield.