Study on the Suitable Critical Period for Late Sowing of Winter Wheat and the Effect

Adjust the sowing date to fit for the climate change and get the high yield of winter wheat is very important in Hebei Province.Taking winter wheat cultivar Ji 5265 as test material,4 sowing dates including October 5,October 9,October 13 and October 17 were desighed,and the sowing rate respectively were 204 kg/hm2,228 kg/hm2,255 kg/hm2 and 288 kg/hm2,the effects of different sowing dates on the yield and growth of winter wheat in Gaocheng City of Hebei Province during 2008-2009 were studied.The results showed that the accumulated temperature before wintering was reduced,the plant tillers number,secondary root number,plant height,spike rate,spike number per unit and the grain number per spike of winter wheat were decreased with the delay of sowing date,and the yield of winter wheat was decreased significantly with the delay of sowing date.Through the regression equation simulation calculation,we recommended that the suitable sowing date was October 5-11,and the reasonable basic seeding number was 307.5-379.5 plants/m2 in Hebei Province.