Morphological And Physiological Monitoring Of Maize Canopy With Different Planting Densities Based On Visible Light Images

Maize is one of the main grain and cash crops in China.It is of great significance to ensure the stability of maize output and further increase it.However,as population continues to grow and arable land resources decrease,increasing yields has become the core of solving food security issues.However,changes in planting density will lead to changes in the growth environment of maize plants.Exploring the relationship between planting density and various parameters of maize is the key to finding the optimum density.Therefore,real-time monitoring of maize is conducive to deeper analysis of the relationship between maize growth and planting density.In this study,on the one hand,related parameters of maize canopy morphology and physiology were measured by traditional methods.On the other hand,the image parameters are obtained based on the visible light image of the maize canopy.The image parameters and the relevant parameters of the canopy morphology and physiology are combined and analyzed to explore the relationship between the two at various planting densities and establish a relevant estimation model to achieve quickly and accurately monitor the morphology and physiology of summer maize canopy with different planting densities.In this paper,two different maize genotypes i.e.Zhengdan 958 and Jinqiu 119 were chosen and 6 planting densities i.e.30,000,45,000,60,000,75,0000,90,000,and 120,000plants·hm^-2were set up for a field trial.This study analyzes the changes of maize canopy morphology and physiology related parameters under different planting densities,and obtains image parameters from maize canopy visible light images,and analyzes the relationship between canopy morphology and physiology related parameters at different planting densities And build an estimation model.The main findings are as follows:（ⅰ）With the increase of planting density,the plant height tended to increase and until a plateau was reached;the leaf area index increased,the individual plant biomass decreased,and the population biomass increased.As the development of maize advances,the chlorophyll content increases slowly in the early growth stage,and then increases at a faster rate,reaching a maximum of 63 to 70 days after sowing.Coverage increased rapidly in the early stages of maize growth,and then the rate of increase gradually decreased,and remained constant within a certain range after reaching the saturation value.（ⅱ）When summer maize is in the middle and late growth stages,under the same growth period and different planting densities,the color parameters r and g were negatively correlated with chlorophyll content,and b was positively correlated with chlorophyll content.As the chlorophyll content decreases,r and g gradually increase,and b gradually decreases,and the color of the leaves shows a tendency to change from green to yellow.The relationship between r and b and chlorophyll content was extremely significant（P<0.01）,which was the main reason for the change of leaf color.（ⅲ）There is a very significant exponential correlation between coverage and plant height （P<0.01）,and the estimation model of plant height for Zheng Dan 958 as y=339.959x²-6.596z+76.817,R²=0.963 and for Jin Qiu 119 as y=382.047x²-7.982z+75.820,R²=0.948（x is the coverage,y is the plant height,and z is the planting density）.（ⅳ）There is a very significant exponential correlation between coverage and leaf area index（P<0.01）,and the estimation model of leaf area index for Zheng Dan 958 as y=9.945x²-3.073x+0.202z-0.237,R²=0.936 and for Jin Qiu 119 as y=12.491x²-5.245x+0.191z+0.146,R²=0.943（x is the coverage,y is the leaf area index,and z is the planting density）.（ⅴ）There was a very significant exponential correlation between coverage and biomass（P<0.01）,and the estimation model of biomass for Zheng Dan 958 as y=62.648e^6.6404x,R²=0.944,and for Jin Qiu 119 as y=51.121e^6.9343x,R²=0.938（x is the coverage and y is biomass）.In summary,the combined analysis of image parameters and canopy morphology and physiological related parameters can more quickly and accurately monitor maize growth information,greatly improving work efficiency.This has practical guidance for daily agricultural production and is of great significance to the application of phenotyping and the development of smart agriculture.