Effects Of Sowing Date And Seed Rate On Crop Growth And Grain Yield Of Winter Wheat Variety Xiaoyan22

Sowing on an appropriate date is of importance for ensuring the better germination of wheat seeds,and therefore could promote the crop growth and yield formation in winter wheat.However,sowing on time is often influenced by harvest of previous crop or adverse weather conditions.Delaying sowing date is a common strategy for handling this agricultural concern in wheat production.In order to determine the critical date for the delayed sowing,the two-year field experiment was conducted in Guanzhong area of Shaanxi Province.The winter wheat variety Xiaoyan22 was used as tested material among five sowing dates,including October 22（normal sowing date）,October 29,November 05,November 12 and November 19 across both experimental years.Under each sowing date treatment,there have two seed rates,one was 150 kg ha^-1（namely conventional seed rate）,the other was to increased seed rate treatment,which were 150,225,300,375 and 450 kg ha^-1 respectively for sowing date October 22,October 29,November 05,November 12 and November 19.The main test results are described as follows:（1）The tillers number and the maximum number of tillers increased with the increase of seed rate.With the postponement of sowing date,the number of tillers and the maximum number of tillers of winter wheat decreased significantly,but the decreasing trend was slowed down by increasing seed rate.However,compared with the normal sowing date,when the sowing date was postponed for two or more weeks,the effect of increasing seed rate on the reduction of the number of tillers of wheat was not significant.In addition,with the delayed sowing date,the emergence period of the highest tiller number of wheat was postponed.Delayed sowing date had no consistent effect on tillers and panicles number.Increasing seed rate significantly reduced the tillers and panicles number of wheat.（2）With the increase of seed rate,the biomass production of wheat increased gradually in each growth period.With the postponement of sowing date,the biomass production at different growth stages showed a significant downward trend,which could be alleviated by increasing seed rate.However,compared with the normal sowing date,when the sowing date was postponed for two weeks or more at the tillering stage and jointing stage,the effect of increasing seed rate on the biomass production was not consistent;at the flowering and maturity stages,the sowing date was postponed for two weeks,the effect of increasing seed rate on the biomass was also not significant.（3）The growth period of wheat is less affected by seed rate.The date of jointing,flowering and maturity of wheat was delayed with the delay of sowing date.Leaf area index（LAI）decreased with the delayed sowing date and increased with the increase of seed rate.When sowing date was delayed for one week,the LAI of wheat at flowering stage was the largest under the condition of 225 kg hm^-2 seed rate.In maturity stage,the plant height of wheat decreased significantly with the delayed sowing date,but increased seed rate had no significant effect on plant height.Delayed sowing had little effect on LAI at flowering stage and plant height at maturity stage,however increased seed rate would increase LAI of wheat at flowering stage,but had no effect on plant height at maturity stage.（4）The number of panicles per unit area increased significantly with the increase of seed rate,while the grain number per panicle and grain weight decreased.With the delayed sowing date,the number of spikes,grains per spike and 1000-grain weight all decreased,but with the increase of seed rate the decreasing trend of the spike number was slowed down,while the decreasing trend of the grain number per spike and thousand grain weight increased.In the treatment of increased seed rate,there was no significant difference between the spike number of wheat delayed by one week and the normal sowing date,but there was no significant difference between the number of grains per spike and thousand grain weight of wheat at each sowing date and the normal sowing date.In the two-year wheat yield,the wheat yield increased with the increase of seed rate.When sowing date is delayed,the yield of wheat decreases dramatically,which can be slowed down by increasing seed rate.However,compared with the normal sowing date,the effect of delaying sowing for two weeks or more is not consistent.The above results showed that sowing date and seed rate have a great impact on wheat yield and the associated yield components,but the effect of sowing date is greater.The sowing date of October 29（delayed for one week）is the critical period for delayed wheat sowing in Guanzhong area of Shaanxi Province.（5）When sowing was delayed,the protein content,wet gluten content,water absorption ratio,starch content,sedimentation value and dough formation time increased,while the bulk density and flour yield decreased.With the increase of seed rate,the protein content,wet gluten content,water absorption,starch content,dough formation time,bulk density and flour yield of wheat did not change significantly.In summary,with the delayed sowing date,wheat yield decreased,and the shortage of panicles could be alleviated by increasing seed rate.However,compared with the normal sowing date,the effect was not consistent after delayed two or more weeks.The results showed that the critical date of delaying sowing was October 29 under the increasing seed rate.Sowing date and seed rate have a significantly impact on yield,its components and grain quality,but sowing date has a greater impact than seed rate treatment.Sowing date treatment mainly affected the grain yield through influencing the panicle number per unit area.