Effects of Late-sowing on Physiology and Yield Characteristics of Winter Wheat Leaves in Northern Henan Province

With Zhoumai 18 as field experimental material,effects of late-sowing on leaves'physiology and yield characteristics of winter wheat in northern Henan province were studied.In this experiment,4 sowing dates corresponding to 4 sowing density were arranged in Xunxian Institute of Agricultural Sciences during 2008-2009.The sowing dates were 18th Oct(T1),23rdOct(T2),28th Oct(T3)and 2ndNov(T4).The results showed that late-sowing affected NR activity in leaves strongly in earlier stage,while chlorophyll content in middle stage.These influences tended to weak in later stage,and the differences among 4 sowing dates were not significant.Late sowing time with increasing sowing density was not really effective on dry matter accumulation per stem over-ground.In mature period,dry matter accumulation per stem under T1 was 3.14g,which was the highest among these 4 treatments.Judging from the grain yield characteristics,late-sowing influenced the grain number per ear(the grain number under T4 treatment was 7.3 less than T1 treatment)and grain weight(the 1000-seed-weight under T1 treatment was 43.63g,significantly higher than T4 treatment)significantly,which led to the lower grain yield.In this experiment,the grain yield tended to be highest under T1,which reached 10354kg/ha,22.80% higher than T4.From the above result,the appropriate sowing date of winter wheat was 18th Oct in northen Henan.