Analysis Of Precipitation, Reference Crop Evapotranspiration And Risk Of Winter Wheat In The North China Plain

This paper analysed the spatial-temporal distribution of precipitation and reference crop evapotranspiration during growth periods of winter wheat in North China Plain. It was based on 322 meteorological observing stations data and yield data of winter wheat. Crop water deficit index was used in this paper to analyze the water deficit condition of winter wheat. It also analysed the spatial-temporal distribution of crop water deficit index and the drought risk of winter wheat. The soil moisture was assumed, when analyzed the crop water deficit index. zero soil moisture and relative soil moisture was 45%, 55%, 65%, 75%, 85% were all included. The main conclusions were aummarized as follows:(1) The spatial distributions based on both are consistent generally, but there is large difference in some terrain areas, which has big volatility. The results of variety of spatial and temporal distribution based on standard stations are reliable. However, the results of all piedmont plain and region near mount should be used carefully in North China Plain When make actual agricultural production decisions.(2) There is a sigenificant increased trend of precipitation duiring growth periods of winter wheat from 1961 to 2010 in North China Plain. The degree of water decifit will decreases with the increase of precipitation duiring growth periods of winter wheat. So the drought risk of winter wheat will reduce.(3) There is a sigenificant decreasing trend of reference crop evapotranspiration duiring growth periods of winter wheat from 1961 to 2010 in moste area of North China Plain. Only in northeast of Hebei, Beijing, Tianjin, northeast of Shandong and north of Henan, the reference crop evapotranspiration was increased.(4) There is an unconspicuous temporal variation trend of crop water deficit index. The spatial change trend is increased with the increase of latitude. In addition, soil moisture significantly reduced the rate of water deficit of winter wheat. It was a little difference between 75% relative soil moisture and adequate soil moisture.(5) The drought risk of winter wheat was increased with increasing latitude. Soil moisture significantly reduced the drought risk of winter wheat. The drought risk was caused by below normal precipitation, when the relative soil moisture reaches 75% or more. The drought risk will increase in north of plain, when the relative soil moisture below 55%.(6)The studys have shown that soil moisture is an important part of water sources for winter wheat, so it can not be ignored. This will exaggerate the drought risk if ignore it.