| Summer maize yield potential is the maximum yield of summer maize in per unit area. How to make the filed yield attain or near to the yield potential is the key to resolve the foodstuff problem. The influencing factors of summer maize yield potential are mainly cultivars, cultivation management measures and climatic conditions. The study is to determine the impact of each factor on summer maize yield potential, meanwhile, to provide support for the increase of summer maize yield under variable climatic conditions. With the utilization of hybrid-maize model and fifty-year meteorological data, the yield potentials of the primary cultivars in each year (Baimaya in 1995s, Zhengdan-2 in 1970s, Yedan-13 in 1990s, Zhengdan-958 in 2000s) have been simulated in Huanghuaihai Area, China. The influencing factors of summer maize yield potential was analyzed, the proportion of each factor in the yield potential and the method of approach the yield potential was analyzed. The main result was as follows.1. Integrated the varieties, planting measure and climate condition, yield potential of summer maize appear obvious decreasing trend with the changes of years. The absolute difference between actual yield and yield potential appear increasing trend, but small change in ratio. The difference between actual yield and yield potential decrease gradually.2. The varieties factor has gradually decreasing impact on summer maize yield potential with the data from 1950s to 1970s, 1970s to 1990s, 1990s to 2000s, 22%±, 16%±and 12%±, respectively; the factor of cultivation management measures has gradually increasing impact with high proportion with data from 1950s to 1970s, 1970s to 1990s, 1990s to 2000s, 68%±, 69%±and 79%±, respectively; in general, climatic conditions factor exerts variable impacts on yield potential in different years with the data from 1950s to 1970s, 1970s to 1990s, 1990s to 2000s, 10%±, 15%±and 9%±, respectively. In addition, the influence differences s are insignificant in sizes and cultivars with large changes in different years, especially in the year with high temperature and rainfall changes, which exert large impact on yield potential.3. The varieties'parameters with higher effection are potential grain number, maximum photosynthetic rate, and initial efficiency of radiation utilization. The maximum photosynthetic rate has a significant positive correlation with the yield potential. The yield potential increase signifitantly with the increase of the potential grain number and the potential filling rate in some extention.4. The effection of planting measure to yield potential will increase gradualy. The rational planting measure will increase yield potential effectively. Increasing the planting density and N fertilizer, derfering the sowing date were the effective measure to increase the yiled potential.5. The effectiong of climate to the yield potential will be higher with the increase of the mean temperature in maize growth period and higher difference of rain among years. The mean tempeture in maize growth period increased gradually in the past fifty years. The increase value is about 1.2℃. Yield potential of summer maize appear obvious decreasing trend with the increase of the mean tempeture in maize growth period. Meanwhile, rainfall is a very importment factor to effect the yield potential in maize. The study indicates that rational cultivation measures'application would release or eliminate the influence of climatic conditions, therefore, increase the yield of summer maize. |
