[Temporal and spatial variation of water requirement of winter wheat and its influencing factors in Henan Province, China].

Based on mean meteorological data of ten days in 17 observation stations from 1961 to 2012, the reference crop evapotranspiration was computed using Penman-Monteith formula recommended by FAO. The water requirement of winter wheat in Henan Province was calculated by adopting crop coefficients and the growth stage of winter wheat from the "National Irrigation Experiment Database", and the temporal and spatial distribution, variation and affecting factors in recent 51 years were analyzed by means of time-series analysis and gray relational grade analysis. The results showed that the average water requirement of winter wheat was 345-492 mm in Henan Province from 1961 to 2011, and it was lowest at Lushi station and highest at Mengjin station. The average water requirement of winter wheat was lowest from 1980 to 1989 and highest from 1961 to 1969 at most stations. The water requirement of winter wheat showed a tendency to increase with years at the 7 stations (Xinxiang, Luanchuan, Kaifeng, Xixia, Nanyang, Xinyang and Gushi) , while it indicated a tendency to decline in the other 10 stations. The water requirement of winter wheat in North Henan was higher than in South Henan, and had a high span variation in West Henan. During the growing period of winter wheat, the average daily maximum and minimum temperatures showed a tendency to increase with years, while the average daily wind speed and relative humidity, and the sunshine hours had a tendency to decline. In Henan Province, the water requirement of winter wheat was mainly affected by the average daily maximum temperature and the sunshine hours, and least influenced by the average daily relative humidity.