| Increasing density is one of the important ways to increase corn yield,but with the increase of planting density,it often results in closed populations and reduced light energy utilization efficiency.Therefore,it is important to explore how to change the planting mode to reduce the negative effects of excessive density on plants and to improve the canopy structure of the population.This experiment was conducted at the Mazhuang Town Experimental Station,Tai’an City,the Technical Innovation Center of Maize in Huang-Huai-Hai Region,and the State Key Laboratory of Crop Biology from 2018 to 2019.Using Denghai 605 and Zhengdan 958 as test materials,under the two density conditions of 67500 plants·hm-2and82500 plants·hm-2,two planting modes of parallel planting and stagger planting were set up.The effect of density on summer maize yield and photosynthetic characteristics is expected to explore and understand the interaction mechanism of wrong planting and density,and propose a suitable planting model for high-yield summer maize,which provides a certain theoretical basis for the scientific planting model of summer maize.The main findings are as follows:1 Effects of staggered planting and plant density on physiological characteristics of summer maizeAt the same density,the LAI and uniformity of the stagger planting were higher than that of the parallel planting at the critical period.In terms of dry matter accumulation,except for the"Zhengdan 958"planting of the wrong planting at a lower density in 2019,which is slightly lower than the planting of the parallel plant,the other treatments in 2018 and 2019showed that the planting of the stagger plant was higher than that of the parallel plant.Under the same planting pattern,the LAI,dry matter accumulation,plant height,and ear height of the two varieties of maize showed high density>low density,and the uniformity of the population showed high density<low density.2 Effects of staggered planting and plant density on light distribution and light energy interception rate of summer maizeThe angle between stem and leaf under the stagger plant was higher than that of the parallel plant,but there was no significant difference.It can be seen that the plants planted with the stagger plants have more space,the competition between individuals is reduced,and the leaves are more flat than the parallel plants,so they can intercept more light energy.At the same density,the light energy capture ratio of the upper layer is higher than that of the stagger planting,and the light energy capture ratio of the lower layer is not significantly different among the treatments.The light energy capture ratio of the entire plant is consistent with the upper light energy capture ratio.Under the same planting pattern,the light energy capture ratio of the entire plant and the light energy capture ratio of the upper layer show a rule of high density>low density,and there is no obvious rule of the effect of density on the light energy capture ratio of the lower layer.3 Effects of staggered planting and plant density on photosynthetic characteristics of summer maizeUnder the same planting pattern,the Pn,PEPC activity,Rubisco activity,Fv/Fm and chlorophyll content of the two varieties of maize showed a law of low density>high density.Rubisco activity and PEPC activity decreased at a higher density as the growth period progressed.It can be seen that increasing the density will increase the leaf senescence rate,which is not conducive to plant photosynthesis.At the same density,Pn,PEPC activity,Rubisco activity,Fv/Fm,and chlorophyll content all appeared as stagger planting>parallel planting.Comparing the decline in the late growth period,it can be found that the decline in Pn,enzyme activity,and chlorophyll content of the two varieties of maize under high density are all manifested as stagger planting<parallel planting,and there is no obvious law at low density.It can be found that the stagger planting can enhance the photosynthesis of the plant,make the plant senescence more slowly,and help maintain a relatively high photosynthetic intensity.4 Effect of staggered planting and plant density on yield and its components of summer maizeIn terms of yield,the planting of the stagger plant increased by an average of 4.9%compared with the planting of the parallel plant.Compared with the parallel plant advantage,the stagger planting model has obvious advantages,and has a certain increase in yield.The yield increase of the stagger planting was 3.8%（low density）and 6.1%（high density）.It can be seen that the stagger planting increasing-effect was higher at a density of 82500plants·hm-2.The law of grain yield is consistent.The 1000-kernel weight and the number of spikes per ear decreased with the increase of planting density.The planting of the stagger plant was higher than that of the parallel plant.The above results show that the effect of stagger planting on dry matter accumulation and photosynthetic characteristics of summer maize is significant.The stagger planting can significantly improve the canopy structure of the population,optimize the lighting conditions of the population,and enhance the photosynthetic performance and material production capacity of the population.In this way,under the premise of ensuring the number of groups,the competition between individual plants in the group for light and temperature resources can be weakened,and the individual development potential of the corn can be fully exerted,so that the maize group and the individual can develop in coordination,and the maize yield can be improved.Under the conditions of this test,comprehensive analysis believes that the stagger planting model under 82500·hm-2density conditions performs best,and can provide a reference for the establishment of a high-yield model of summer maize. |
