Factors Study Affecting The Wetting And Spreading Effect Of Droplets On Rice Leaf Surface

Pesticides are one of the indispensable means of production in agricultural production.Low pesticide utilization poses a serious threat to the environment,biology and human health.How to improve the utilization rate of pesticides is a serious problem that needs to be solved at this stage.The ability of droplets to spread on the surface of plant leaves directly affects pesticide utilization.In order to enhance the wetting and spreading effect of the droplets on the surface of the blade and improve the utilization rate of the pesticide,in this paper,using rice as the research object,the experimental research method was used to study the intrinsic factors and external factors affecting the wetting and spreading ability of rice leaves from the wettability indexes such as contact angle,critical surface tension and retardation angle.The main research contents and related conclusions of this paper are as follows:(1)The contact angle(θ)is the main index to measure the wetting and retention ability of droplets on rice leaves.In order to accurately measure the contact angle of droplets on the surface of rice leaves,the effect of droplet volume on the leaf contact angle of rice was studied.The leaf contact angle,droplet height(h)and droplet contact surface diameter(d)of different droplet volumes were measured experimentally to analyze the change of contact angle with droplet volume.In this way,we can conclude that the droplet volume has a significant effect on the leaf contact angle of the rice,and the change trend of the contact angle is closely related to the droplet height and the contact surface diameter and the growth rate of both.Finally,the paper proposes that the droplet volume used in the rice leaf contact angle experiment should be larger than the volume corresponding to the maximum contact angle of the rice leaf surface,and is preferably controlled within the range of 7.5～20 μL.(2)The effects of variety,surfactant concentration,growth cycle and leaf position on the surface wetting properties of rice leaves were significant.The difference of wettability measurement indexes such as contact angle,critical surface tension and retardation angle of different varieties of rice leaves was significant.In addition,the two factors of rice variety and surfactant concentration have an interactive effect on the wettability of rice leaves.In the same rice,the wettability of leaves in different leaves was not significantly different,but the difference in wettability of different leaves in the same rice was significant.The wettability of rice leaves with different growth cycles was significantly different.With the growth of rice,its wettability decreased first and then increased,and it was the strongest at the flowering stage and the weakest at the mature stage.Finally,orthogonal experiments were carried out to determine the effects of three internal factors on the wettability of rice leaves from large to small: growth cycle>leaf position>variety.(3)The temperature and relative humidity in the air have a significant effect on the contact angle of the droplets on the surface of the rice leaf.With the increase of ambient temperature,the leaf contact angle of rice decreased first and then increased,and reached the minimum at 25 °C.With the increase of relative humidity,the leaf contact angle of rice increased gradually.The two factors of temperature and relative humidity have no interaction on the contact angle of droplets on the surface of rice leaves.The dosage form and concentration of the pesticide have a significant effect on the reduction of the contact angle of the droplet on the surface of the rice leaf,and the effect of the concentration factor is greater than the dosage form.Orthogonal experimental analysis showed that the effect of pesticide dosage form and concentration on the contact angle of droplets on rice leaf surface was more significant than temperature and relative humidity,and the effects are ranked from large to small: pesticide concentration > pesticide dosage form >> relative humidity > temperature.(4)The charge has a significant effect on the contact angle of the droplets on the surface of the rice leaf.The charging voltage,voltage polarity,Na Cl concentration,electrode ring material and specifications can affect the contact angle of droplets on the surface of rice leaves.As the charging voltage increases,the leaf tentacles of the rice first decrease and then increase,reaching a minimum at a voltage of 4 k V,and the contact angle carrying a negative charge is smaller than the positive charge.The leaf contact angle of rice with a negative charge attached to the droplet at 4KV is the smallest.As the Na Cl concentration increases,the contact angle decreases first and then increases,reaching a minimum at a concentration of 4.5%.Both the electrode ring material and the specification can affect the leaf contact angle of the rice,and the brass electrode ring with an inner diameter of 50 mm has the smallest droplet contact angle.In this paper,the effects of droplets on the surface wetting and spreading of rice leaves were systematically studied,mainly including droplet volume,rice variety,leaf position,growth cycle,temperature,relative humidity and charge characteristics.This study provides reference value for the study of the wetting and spreading of liquid medicine on the surface of other plant leaves,and provides theoretical support for further optimizing the precise pesticide application technology and improving the utilization rate of pesticides,leading to formulate a pesticide application scheme with low pesticide loss rate.This has important application value.