Abstract
The dynamics of evaporating sessile droplets on hydrophilic or hydrophobic surfaces is widely studied, and many models for these processes have been developed based on experimental evidence. However, few research has been explored on the evaporation of sessile droplets of surfactant or pesticide solutions on target crop leaves. Thus, in this paper the impact of surfactant concentrations on contact angle, contact diameter, droplet height, and evolution of the droplets’ evaporative volume on rice leaf surfaces have been investigated. The results indicate that the evaporation kinetics of surfactant droplets on rice leaves were influenced by both the surfactant concentrations and the hydrophobicity of rice leaf surfaces. When the surfactant concentration is lower than the surfactant CMC (critical micelle concentration), the droplet evaporation time is much longer than that of the high surfactant concentration. This is due to the longer existence time of a narrow wedge region under the lower surfactant concentration, and such narrow wedge region further restricts the droplet evaporation. Besides, our experimental data are shown to roughly collapse onto theoretical curves based on the model presented by Popov. This study could supply theoretical data on the evaporation of the adjuvant or pesticide droplets for practical applications in agriculture.
Highlights
Rice is one of the most widely grown crops in the world [1], and severely affected by plant diseases, insect pests, and weeds, all of which are mainly controlled by foliar spraying of pesticide solutions
When the concentrations are lower than critical micelle concentration (CMC) (0.001%, 0.005%), more than 2000 seconds is needed for the dynamic surface tension curves to reach the equilibrium, and such long time will lower the measurement precision on account of the water evaporation
Evaporation of the water droplets containing different concentrated surfactants on fresh rice leaf surfaces are shown to occur by a mixed mode for droplets with concentrations of 0.001% and 0.005%, whereas both a contact radius (CCR) and a mixed mode occur in water droplets and those with concentrations of 0.01%, 0.05%, and 0.10%
Summary
Rice is one of the most widely grown crops in the world [1], and severely affected by plant diseases, insect pests, and weeds, all of which are mainly controlled by foliar spraying of pesticide solutions. Transportation of an active ingredient is a complicated process, which starts with the preparation of the spray solution followed by atomization, translocation, and impact between the solution and the leaf surface [2]. The leaf surface characteristics, spray solution properties, and environmental conditions affect the spray deposition of pesticide solutions onto the target crop leaves. Thereby, the evaporation behavior of droplets significantly affects the deposition formation, drying process, penetration and translocation within the target crop tissue, and bio-efficiency.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
