Pathways And Mechanism For Matching Efficient Population Construction Of Spring Maize To Heat Resource

In the choice and large area popularization of Mechanical grain-harvesting variety,about how to shorten ripeness period for dehydration time,which actually proposes the new challenge for the full utilization of north spring maize yield and heat.As a result,revealing coordinated mechanism of Mechanical grain-harvesting variety in different heat situations,especially on how to realize yield and heat utilization efficiency through reasonable planting density,which could provide theoretical basis for high yield and efficiency cultivation and large spread of this variety.Based on four ecological regions with different heat conditions in the west of Northeast China（Inner Mongolia）,this thesis conducted density network experiments with different types of maize varieties as materials,and analyzes response laws of heat resource conditions and density on different types of maize varieties’stage development,yield formation and heat utilization efficiency（HUE）.The main research results are as follows:（1）The suitable density of Mechanical grain-harvesting variety decreased linearly as the heat resources increase.The suitable density increased by 0.17 million plants·ha^-1 for every 100℃decrease of annual accumulated temperature≥10℃in the ecological region.In the area with limited heat resources,the balance of pre-silking and post-silking heat resources and the full accumulation of pre-silking biomass become the key factors,and the suitable density was 88,000 to 92,000 plants·ha^-1.The core is to excavate the potential of post-silking material production in the area with abundant heat and to build a suitable population density of 81,000-83,000 plants·ha^-1.（2）In the region with limited heat（mainly planting early or medium early maturing varieties）,the number of growing days pre-silking and post-silking,accumulated temperature and biomass accumulation ratio of maize kernels variety are all 5:5.The increase of densities was 28,000～31,000 plants·ha^-1 and the increase the yield was20.1～23.3%,and the yield could reach 11.1～12.7t·ha^-1.HUE can be increased by20.6～30.1%.While in the region with ample heat（mainly for medium and late maturing cultivars）,the proportion of growth period days and accumulated temperature pre-silking and post-silking was 4.5:5.5,and the proportion of biomass accumulation pre-silking and post-silking was 4:6.The increase of density of 21,000～23,000 plants·ha^-1 could increase the yield by 6.6～15.5%,and the yield could reach 15.4～16.9 t·ha^-1.HUE can be increased by 8.6～17.5%.（3）Daily mean temperature（T_a）and daily range（T_r）were the core temperature factors affecting the growth and development of maize per-silking and post-silking respectively.The late maturing varieties were planted in region with limited heat,and the T_a at per-silking was low,which prolonged the growth period at per-silking,and leaded to the lack of heat at post-silking,thus reducing the yield and quality.Early maturation varieties were planted in region with plenty of heat,and the higher T_a at per-silking made them develop quickly,and the dry matter accumulation was insufficient at per-silking,so that they could not realize their yield potentiality.For ecologically suitable maize kernels variety,T_a at per-silking and T_r at post-silking were increased by 0.1℃each on the premise of reasonable allocation of days about per-silking and post-silking,the biomass accumulation increased 0.71 t·ha^-1 and 0.79 t·ha^-1at per-silking and post-silking.The higher T_a at per-silking and T_r at post-silking were the prerequisites to achieve sufficient material accumulation and rapid grain filling,so as to achieve high yield and suitable Mechanical grain-harvesting.（4）The results of Hybrid-Maize model simulation and field validation demonstrates that the replace of main cultivar with maize kernels variety and densification20,500～24,500 plant·ha^-1 in the area with limited heat could increase the yield by22.8～33.5%and increase the HUE by 23.6～32.7%.The yield increased by 6.3～18.6%and HUE increased by 16.3～20.7%in the area with sufficient heat when the ripening time was unchanged and the densification was increased by 21,000～23,000 plant·ha^-1.