Effects Of Sowing Date On Yield And Utilization Efficiency Of Light And Temperature Resources Of Different Summer Maize Varieties

Adjusting the sowing date is one of the important cultivation measures for increasing the yield and efficiency of summer maize.In this study,3 hybrids were selected,namely early-maturing variety（Shaandan 650）,medium-maturing variety（Zhengdan 958）and late-maturing variety（Dongdan 60）as the test materials,and 3 sowing dates were set:3 June（early sowing）,9 June（medium sowing）,and 15 June（late sowing）.Systematically compared their indices differences of different cultivars under different sowing conditions by measuring yield,light-temperature resource utilization efficiency,yield composition,dry matter accumulation and transport,and leaf area.Subsequently,comparatively analysis of yield potential,potential light-temperature resource utilization efficiency and actual observations through the DSSAT model,which explored the optimal sowing dates for hybrids.These findings will provide theoretical guidance for the actual production of summer maize.The main findings are as follows:（1）The DSSAT model was used to correct the genetic parameters.There was a significant linear relationship between the measured and simulated values of maize flowering,maturity and yield,with R² greater than 0.73（P<0.05）,and the standard error less than 7.6%.Therefore,the genetic parameters calculated by the model were suitable for the simulation of summer maize in the region.（2）The results of growth model and experiment showed that optimizing the sowing date of different maize hybrids can significantly increase maize yield and narrow yield gap.In the2-year experiment,the highest yield of late sowing in Shaandan 650 was 9408.83 kg·ha^-1,the highest yield of middle sowing in Zhengdan 958 was 10464.1 kg·ha^-1,and the highest yield of early sowing in Dongdan 60 was 10618.7 kg·ha^-1.However,according to the response of each variety to the change of sowing date simulated by the model,the order of climate adaptability and production potential of different hybrids was Zhengdan 958>Dongdan 60>Shaandan 650.On the basis of the current production conditions,the yield gap of Zhengdan 958 was the smallest,which was significantly lower than that of Dongdan 60 early sowing and Shaandan650 late sowing.It shows that Zhengdan 958 is suitable for sowing around 9 June to obtain high yield.（3）Under different sowing dates,the average light and temperature resource utilization efficiencies of medium-maturing variety Zhengdan 958 were the highest at 4.81 kg·ha^-1MJ^-1and 5.36 kg·ha^-1℃^-1,respectively,which narrowed the gap 16.53%and 16.3%than the simulated values.With the delay of sowing date,the total growth period days,cumulative accumulated temperature,solar radiation and rainfall of different hybrids decreased gradually.When the medium-maturing variety Zhengdan 958 reached 1950.83°C and the radiation reached about 2177.25 MJ·m^-2,compared with Shaandan 650 late sowing,the utilization efficiency of light and temperature resources increased by 8.46%and 6.47%,and compared with Dongdan 60 early sowing,the growth period was shortened by 9 days.It can be seen that the growth period of medium-maturing variety Zhengdan 958 is suitable,and the accumulated light and temperature resources are more,which can significantly improve the utilization efficiency of light-temperature resources and increase production and income under medium sowning conditions.（4）Yield was significantly positively correlated with grain number per spike and 1000-grain weight,while grain number per spike was significantly negatively correlated with 1000-grain weight.Under the same inter-annual sowing date,the 1000-grain weight of medium-maturing variety Zhengdan 958 was higher than that of early-maturing variety Shaandan 650and late-maturing variety Dongdan 60,but the grain number per spike was lower than them.Therefore,increasing the grain number per spike of Zhengdan 958 is the key to increasing yield.（5）Although early sowing can effectively promote plant growth and dry matter accumulation before flowering of medium and late-maturing hybrids,combined with yield analysis showed that dry matter accumulation and translocation after flowering were the main sources of high yield.Under different sowing dates,dry matter accumulation after anthesis,contribution rate of dry matter transport to grain,average filling rate and 100-grain weight of Zhengdan 958 were significantly higher than other hybrids.It shows that the medium sowing of Zhengdan 958 was beneficial to promote the accumulation and transportation of dry matter after flowering,and then obtain higher yield.（6）In the 2-year experiment,the leaf area index of different hybrids and sowing dates increased first and then decreased with the progression of growth period in the same year.The leaf area index of mid-late maturing hybrids at silking stage was higher than that of early-maturing hybrids,and the leaf area index of late sowing treatment was significantly higher than that of early and middle sowing.The high temperature at flowering stage and the low temperature at maturity stage were significantly negatively correlated with the relative yield.When the temperature reached above 34°C in the pre-flowering 5 days or below 14°C in the10 days before maturity,the relative yield showed a significant downward trend.The early sowing treatments of Shaandan 650 and Zhengdan 958 suffered continuous high temperature stress above 36°C at silking stage,while the middle and late sowing of Dongdan 60 suffered low temperature stress with an average of 5 days less than 14°C at late filling stage.It can be seen that the leaf area of medium-maturing variety Zhengdan 958 is larger than that of early-maturing variety,and the growth period is shorter than that of late-maturing variety.Under the condition of medium sowing,it can avoid high temperature at flowering stage and low temperature at filling stage,which is beneficial to machine harvest and high yield.Therefore,through the model simulation and field experiment,we conclude that the Zhengdan 958（medium-maturing）under the condition of medium sowing（9 June）not only avoids the high temperature stress at flowering stage and low temperature stress at filling stage,stabilizes the number of grains per spike,improves the grain filling rate and increases the 1000-grain weight,but also prolongs the light and temperature resources in the growth period,improves the utilization efficiency of light and temperature resources,increases the leaf population area,promotes the accumulation and transportation of dry matter before and after flowering,and thus increases yield and efficiency,compared with Shaandan 650（early-maturing）and Dongdan 60（late-maturing）under different sowing dates.