| The Qitai area of Xinjiang has sufficient radiation and heat resources in China.The process of mining the high-yield potential in this area from 2009,it has set a national high-yield record for five times and reached 24.95 Mg/ha in 2020.Every year,10-90 high-yield plots of density-tolerant and high-yield varieties are screened from all over the country,each plot is 1.5-2 mu(666.7 m~2),and high-density planting is adopted.The density is.Under ideal conditions of no water and fertilizer restrictions,no pests and weeds stress,planted in 105000,120 000 and 135 000 plants/ha.From 2010 to 2021,263 varieties were tested and 468valid data for high-yield were collected,yield ranges were from 9.8 Mg/ha to 24.9 Mg/ha.From yield components,population structure,biomass production and distribution,etc.,explored the ways of high-yield breakthroughs in maize,clarified the restrictive factors and physiological mechanisms for further improvement of yield at different yield levels.The main results were shown as follows:1.Identify the yield breakthrough approach with increasing the number of harvested ears and population grains,and increasing the 1000-kernels weight and grain yield per plant.Harvested ears,grains number per ear,1000-kernels weight and grain yield per plant of high-yielding varieties(>21 Mg/ha)were 11.8(9.4-14.1)10~4/ha,498.7(268.5-616.8),383.2 g(291.2-42.6 g)and 0.189 kg(0.158-0.274 kg),respectively.2.The study found that with the increase of the yield level,the structure of high-yielding maize varieties showed a decrease in ear ratio,leaf angle above ear,and an increase in leaves number above ear,internode length,LOV above ear,LAI and leaves area duration.From 15Mg/ha to 21 Mg/ha,internode length above ear increased by 0.42 cm,LOV above ear increased by 1.10,LAI at silking stage and at maturity stage increased by 0.06 and 0.22,respectively.The high-yielding varieties(>21 Mg/ha)have better canopy structure,the ear ratio,the LAI at silking and maturity,and leaves number above ear are 0.39(0.35-0.45),7.2(4.6-9.4),4.7(2.7-6.5),and 6.8(6.0-8.3),respectively.The internode length,the leaves angle,and LOV above the ear are 20.1 cm(19.3-22.1),18.0°(15.7-22.3)and 48.6(45.0-55.3),respectively.The internode length,leaves angle,and LOV below the ear are 16.0 cm(14.5-16.3),32.0°(25.6-43.8)and 36.0(33.6-38.5),respectively.The light transmission of the ear layer is 18.5%.3.Yield increased from 13.4 Mg/ha(average yield<15 Mg/ha)to 22.1 Mg/ha(average yield>21 Mg/ha)by 64.9%,biomass and HI increased by 17.7%and 23.5%,respectively.The post-silking and maturity biomass of high-yielding varieties(>21 Mg/ha)were 22.9Mg/ha and 36.5 Mg/ha,respectively,and the ratio of pre-silking biomass to post-silking biomass was about 4:6.The average harvest index was 0.53.The dry weight of grain accounted for 91.1%of the post-silking biomass,the average dry matter transfer rate of vegetative organs was-1.6%,and the average grain leaf ratio was 307.7 g/m~2.Yield mainly depended on larger grain leaf ratio,larger post-silking biomass and HI.4.Using the MC670 variety,the national high-yield records of 22.8 Mg/ha and 24.9Mg/ha were set in 2017 and 2020,respectively.Compared with the high-yield record yield in 2017,the new record yield in 2020 increased by 9.2%,harvest ears per hectare increased by 5.7%,grains number per ear decreased by 3.5%,the 1000-kernels weight did not change significantly,and grain yield per plant increased by 7 g.The breakthrough in yield is due to the increase in harvested ears,the 1000-kernels weight remains unchanged,the decrease in grains number per ear is small,and the grain yield per plant increases significantly.Analysis of the meteorological factors for the formation of high yield found that the average temperature in April and May in 2020 were higher than that in 2017,which was beneficial to the germination and emergence of seeds after sowing;the highest temperature in July is not high,which was conducive to silk pollination and fruiting.The temperature difference between day and night is large,and the respiration consumption is small,which was conducive to early grain filling;the temperature in September is high,and the temperature difference between day and night is large,which is conducive to grain dehydration and maturation.Based on the above research results,the changing trends of yield components,plant structure,biomass production and distribution were clarified from<15 Mg/ha to>21 Mg/ha.The population structure characteristics of>21 Mg/ha high-yielding maize were constructed,and proposed that increasing the number of ears and population grains,and increasing the1000-kernels weight and grain yield per plant are important population yield structure characteristics to achieve breakthroughs in maize yield. |
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