| Planting density is one of the important measures that influence the population structure of winter wheat,and the optimum density of different varieties is not co nsistent.Therefore,it is important to study the reasonable population structure chara cteristics of different winter wheat cultivars in order to make full use of light,heat,water resources and increase grain yield.In this study,a field experiment was con ducted in Gaocheng country Shijiazhuang City in 2018-2019 and 2019-2020.HG35 and JM22 were used in 2018-2019 season.However,only HG35 2019-2020 was us e in 2019-2020.The experiment was designed as split plot arrangement,with cultiva rs as main plot and plant density as sub plots.In 2018-2019,8 planting densities were conducted as:180×04(D180),240x104(D240),300×104(D300),360×104(D360),420×104(D420),480×104(D480),540×104(D540)and 600×104(D600)plants/hm2.In 2019-2020,6 planting densities were conducted as:180×104(D180),240×104(D240),300×104(D300),390×104(D390),48×104(D480),570×104(D570)plants/hm2.The main results were summarized as follows:1.In 2018-2019,the spike numbers of HG35 ranged from 530.0 to 750.0×104/hm2,and the spike numbers of JM22 ranged from 692.3 to 853.4 ×104/hm2.In 2019-2020,the spike numbers of HG35 ranged from 796.7 to 940.0×104/hm2.Spiking percentage of main stem increased,and spiking percentage of tiller decreased with the increase in plant density.The dry matter accumulation of the two varieties in each growth period gradually increased with the increase of planting density.The dry matter accumulation in D180,D240 and D300 were significantly lower than that in D480,D540 and D600 in the early growth period.However,the difference in dry matter accumulation between different densities was gradually decreased after anthesis(does not include anthesis).LAI presented a single-peak curve change with the advancement of growth process,reached its maximum value at booting stage,and declined rapidly after flowering.In 2019-2020,there was no significant difference between plant densities in LAI after anthesis.2.In 2019-2020,The decline rate of top 3nd leaf was higher than that of top 2 nd leaf and flag leaf,and the decline rate of top 3nd leaf,top 2nd leaf and total green leaf at low density was slower than that of high-density.The results indicated that low density was beneficial to delay the senescence of leaves.In 2018-2019,the LAI of top 2nd leaf,top 3nd leaf and top 4nd leaf of HG35 increased with the increase of plant density.There was small difference in LAI of flag leaves between different densities(except D180),while JM22 mainly increased the LAI of top 3nd leaf and top 4nd leaf.In 2019-2020,the LAI of top 4nd leaf of HG35 increased with the increase of density.LAI with high density treatment(mainly higher LAI of top 4nd leaf)does not necessary to improve yield due to the top 4nd leaf is located at the bottom of the canopy,which resulting in poor ventilation and light transmission.The results also indicated that low-plant density could achieve higher LAI of flag leaf and top 2nd leaf through increasing the total stem numbers,which is conducive to the improvement of yield.In 2018-2020,the specific leaf weight gradually decreased with the increase of density.In 2019-2020,the specific leaf weight of flag leaf,top 2nd leaf and all green leaves was positively correlated with grain yield at grain fill stage of winter wheat.The higher specific leaf weight under low-plant density was beneficial to improve grain yield.3.In 2018-2019,at the end of grain fill stage,the light interception rates of HG35 and JM22 under D600 only increased by 3.1%and 13.1%as compared with D180.In 2019-2020,D570 got the highest light interception rate of HG35 but there was no significant difference between different plant densities.The light interception rate of D570 in the middle and the end of the grain fill stage was only 0.5%and 0.7%higher than that of D180.The results showed that low-plant density could achieve higher light interception rate due to the higher total stem numbers.In 2019-2020,the flag leaf interception rate of D180 and D240 was lower than that of high density.However,there was no significant difference in light interception rate between top 2nd leaf,top 3nd leaf and the bottom of the canopy.4.There were significant influence of plant density on yield and yield components of winter wheat.The spikelet length,spikelet number and 1000-grain weight of HG35 and JM22 decreased with the increase of density in 2018-2020 seasons.The kernel numbers per spike significantly decreased with the increase of plant density.In 2018-2019,HG35 achieved the higher grain yield in D360 and D420,which were 8537.6 and 8410.6 kg/hm2,respectively.The JM22 achieved the higher grain yield in the D240 and D300,which were 8458.8 and 8354.7 kg/hm2,respectively.In 2019-2020,the higher grain yield of HG35 was obtained at D180 and D240,which were 8270.9 and 8503.0 kg/hm2,respectively.In conclusion,In the years when the accumulated temperature in spring is insufficient at recovery stage of winter wheat,the large-spike variety HG35 with relatively dispersed plant shape and medium tillering power should be increased in density to obtain high yield,which can achieve higher yield in the range of D360-D420;however,the highest yield density of JM22,which has a compact plant shape and stronger tillering ability,is lower than HG35,and can achieve high yield in the range of D240-D300.In the years with higher accumulated temperature,the lower density range of D180-D240 obtained higher grain yield through increase spike numbers,1000-kernel weight and kernel numbers per spike of HG 35 with medium tiller capacity. |
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