Study On The Mechanism Of Annual Yield Formation And Efficient Utilization Of Climate Resources In Double-maize System

The single planting pattern,misallocation of light-temperature resource of traditional cropping system,serious waste of resources and weak disaster resistance are being increasingly influenced by the changing of climate and production conditions in multi-harvest regions of China.However,incremental changes in traditional cropping systems have limited the increasing of grain yield and resource efficiency.In recent years,in order to take full advantage of high photosynthetic and high resources utilization efficiency of C₄crop-maize,new cropping systems such as double-maize system,spring maize-late rice and early rice-autumn maize were established in the Huang-huai-hai Plain and the Middle Reaches of the Yangtze River.However,the development of the double-maize system is still limited by the lack of scientific basis for variety selection and the unreasonable combination of varieties in double season,which have restricted the increasing of grain yield and resource efficiency.Therefore,based on the ecological adaptability of varieties,the study selected the suitable variety types and the combination in the two seasons.Furthermore,to study the formation of yield,the characteristics of the allocation and utilization of climate resources and the quantitative matching relationship between yield and climate resources.And then,to reveal the physiological and ecological mechanism of the establishment in double-maize system and eventually illustrate the regulation effect of density on the formation of yield in the two seasons.The main results are as follows:（1）We clarify the high production and high efficiency combination of varieties and the difference of variety selection in double-maize system of the Huang-huai-hai plain and the Middle Reaches of the Yangtze River.The effective accumulated temperature of the first and the second season varieties in the Huang-huai-hai plain should meet 1230℃-1345℃and 1365℃-1430℃,and the suitable combination of the two seasons are LH,MM and HL.The effective accumulated temperature of the first and the second season varieties in the Middle Reaches of the Yangtze River should meet 1450℃-1520℃and 1350℃-1450℃,and the suitable combination of the two seasons are LH,MM,MH and HM.（2）In order to explore the characteristic of resources distribution and regional differences in the two seasons for double-maize system with high production and high efficiency between the Huang-huai-hai plain and the Middle Reaches of the Yangtze River.In the Huang-huai-hai plain,the accumulated temperature distribution rates（TDR）of double-maize system（LH）in the two seasons are 47%and 50%,respectively,and the accumulated temperature rate between two seasons（TR）is 0.9.The accumulated temperature of LH in the two seasons is partial distribution of the second season.In the Middle Reaches of the Yangtze River,the TDR of double-maize system（HM）in the two seasons are 49%and 46%,respectively,and the TR is 1.1.The accumulated temperature of HM in the two seasons is partial distribution of the first season.According to the indexes,the resources distribution between the two seasons can be allocated by selecting varieties,and make the optimal distribution scheme of two seasons reasonably.Fully exploiting regional light-temperature resources and playing the maize’s capacity of the high efficient utilization of resources,which is important to increase yield and resources use efficiency in the Huang-huai-hai Plain and the Middle Reaches of the Yangtze River.（3）In order to explore the yield potential of double-maize cropping system,the relationship between yield and climatic factors is investigated.The difference of dry matter accumulated（DM）is the main reason of yield difference in double-maize system.In the Huang-huai-hai Plain,no significant difference in DM of the first season,and the difference in DM of the second season led to the difference in annual DM.Temperature is the determining meteorological factor for regulating GY and DM of double-maize system.When the GDD of pre-silking and post-silking stage are 1040℃and 660℃in the second season,respectively,the DM is the greatest.In the Middle Reaches of the Yangtze River,temperature and precipitation are the main meteorological factor for regulating GY and DM of double-maize system.In the first season,when the GDD,MT,T_max,T_min of pre-silking stage are 762.2℃,18.5℃,23.3℃and 14.4℃,respectively,and GDD,MT,T_max,T_min of post-silking stage are 832.3℃,28.1℃,31.7℃and 24.3℃,the DM is the greatest.In the second season,when the GDD,MT,T_max,T_min of pre-silking stage are 948.9℃,28.6℃,32.5℃and 24.6℃,respectively,the GDD,MT,T_max,T_min and P_rfrom silking to maturity during post-silking stage are 659.6℃,21.8℃,26.7℃,16.9℃and 82.9mm,the DM is the greatest.（4）Researched the effect of density on the ecological adaptability of double-maize system.In the Huang-huai-hai Plain and the Middle Reaches of the Yangtze River,the GY and DM of double-maize system are the greatest when varieties under the condition of the high-density(9.75×10⁴株ha^-1)in the first season and the low-density(6.75×10⁴株ha^-1)in the second season.The reasonable density of the two seasons can promote the yield of double-maize system,and realize the synchronous improvement of the annual yield and resource efficiency.In the Huang-huai-hai Plain,comparing with the other combinations（MM and HL）,the annual yield of LH combination of double-maize system increased by13%and 28%under the condition of reasonable planting density in the two seasons.In the Middle Reaches of the Yangtze River,comparing with the other combinations（LH,MM and MH）,the annual yield of HM combination of double-maize system increased by 47%,28%and 30%under the condition of reasonable planting density in the two seasons.