Effect Of Planting Density On Population Quality And Yield Formation Of Uniformly Sown Winter Wheat

In Planting density affects the population structure of winter wheat,and the differences in tillering characteristics and light energy utilization capacity of different spike types cause changes in environmental factors,which in turn affect yield formation.In order to investigate the suitable plant spacing and planting density for different spike types of wheat for stable yield increase.In this experiment,a two-factor split-zone test was conducted with the large-spike variety Xing Dong50（V₁）and the multi-spike variety Sangtamu 4（V₂）as the test materials,with the variety in the main zone and five planting densities of 123×10⁴plants/hm²,156×10⁴plants/hm²,204×10⁴plants/hm²,278×10⁴plants/hm²and 400×10⁴plants/hm²in the sub-plots respectively.The differences in population quality,photosynthetic characteristics,canopy structure and microenvironment and yield of uniformly sown winter wheat were studied from D₁to D₅.The main findings were as follows:1.Planting density had a regulating effect on the population stem tiller number of winter wheat.The population stem tiller number of both types of winter wheat increased with increasing planting density,reaching a maximum at 400×10⁴plants/hm²,while the stem tiller spike rate was highest at 123×10⁴plants/hm²,with the average values of 42.30%and 49.89%in two years,respectively.The increase in post-planting density led to rapid degradation of ineffective tillers.Increasing planting density led to faster decline in LAI in the later stages of winter wheat fertility,and the difference in spike length with planting density was not significant.2.The dry matter accumulation of winter wheat behaved differently under different densities.The dry matter of the spike after flowering was significantly affected by planting density,and the low density treatment favored the increase of dry matter of the spike.The dry matter transfer rate was highest in the leaves and lowest in the rachis and glumes.The dry matter contribution rates of the two types of winter wheat were not consistent,with V₁having the highest post-flowering dry matter contribution rate at 278×10⁴plants/hm²,75.15%and 78.69%,respectively,and V₂having the highest post-flowering dry matter contribution rate at 156×10⁴plants/hm²,71.39%and73.23%,respectively.3.The SPAD values of both types of winter wheat reached their maximum at the filling stage,and the SPAD of V₁varieties decreased with increasing planting density before flowering,indicating that increasing density affects the SPAD of wheat.increasing planting density leads to a decrease in net photosynthetic rate（Pn）,stomatal conductance（Gs）and transpiration rate（Tr）of winter wheat flag leaves,as shown by D₁>D₂>D₃>D₄>D₅.4.Increasing planting density decreases the stem resistance of winter wheat to overturning.Increasing planting density increased plant height,but decreased basal second internode stem thickness.The stalk folding resistance of both spike types of winter wheat showed D₁>D₂>D₃>D₄>D₅at different densities from the filling stage to the milking stage,and the center of gravity height of V₁variety increased by 11.97%and 9.97%compared with V₂variety at 400×10⁴plants/hm²at maturity,while the fresh weight of single stems decreased with increasing density,and the folding The index of collapse was 12.41%higher on average for V₁variety D₅treatment than D₁treatment,and 24.89%higher on average for V₂variety D₅treatment than D₁treatment,indicating that the greater the planting density,the more prone to collapse.5.Planting density affects the leaf area of winter wheat,and the maximum difference between the flag leaf area of the two medium types of winter wheat is 8.72 cm²and 4.99 cm²,respectively,and increasing density decreases the flag leaf area.The higher the density,the more compact the plant is,the smaller the average canopy leaf inclination,and the canopy temperature and canopy CO2 concentration will be reduced.The average temperature difference between the upper and lower layers of the two types of winter wheat was 1.1℃and 1.7℃respectively.Canopy relative humidity was more variable in the upper layer of wheat.6.Planting density affects the yield and yield components of winter wheat.The number of grains and thousand grain weight of the two spike types of winter wheat increased with planting density as D₁>D₂>D₃>D₄>D₅.Yield showed a trend of increasing and then decreasing with increasing density,with the highest yield of Xing Dong 50 at D₄density,averaging 9374.86kg/hm²for two years,and the highest yield of Santamu 4 at D₂density,averaging 9513.79 kg/hm²for two years.Even sowing improves plant uniformity and increases the transfer of nutrient organ dry matter accumulation to the seeds.Adjusting planting density can increase the effective number of spikes of winter wheat,thus increasing the yield.The suitable planting density for Xing Dong 50is 278×10⁴plants/hm²,and the suitable planting density for Sangtamu 4 is 156×10⁴plants/hm².