Temporal-spatial variation of elongating time of wheat in Huang-Huai wheat production area

Twenty years data of winter wheat elongating time,varieties,vernalization feature,and average air temperature of every 10 days in spring,occurrence and injury of frost,etc.were collected from 36 agro-meteorological observation stations,which are located in Huang-Huai wheat production area and its around areas.With these data,the main factors that affect the elongating time of winter wheat were analyzed;the function on accumulative probability with time was established and the variations of some main parameters in this area were also analyzed.Finally,the causes for the variation in parameters were discussed and the guidance for the practical production was also proposed.