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Plants use approximately 5% of the water they take in during their vegetation for growth and development, while losing 95% of it through transpiration to cool down. Kaolin use reduces the cooling needs of plants, balances the water use of and helps maintain soil moisture during periods when temperatures rise and irrigation needs increase.
It has been determined that sun rays (UV and infrared wavelengths) are reflected on leaf surfaces when kaolin clay is sprayed on plants (Shellie and King, 2013). As the particle size of kaolin decreases, the degree of UV reflection increases significantly. It is important that the particle size does not clog the tool equipment used and performs the coating feature at an ideal level. Excessive heat, temperature, and light stress on leaf surfaces are reduced with kaolin application. Studies have shown that heat stress on leaves and fruits is reduced with the application without affecting gas exchange in the leaves (Glenn et al., 2001). Many scientific studies have been conducted on the effects of kaolin applications on the conductance (operation) of stomata on leaf surfaces and it has been shown that kaolin applications do not inhibit stomatal activity (Lombardini et al., 2005; Rosati et al., 2006)
Figure 1. Kaolin application on apple tree leaves (Glenn and Puterka, 2005)
Plants try to prevent excessive water loss by closing their stomata in order to maintain their water balance under heat stress. This defense system is extremely necessary for water balance in the plant, but if the stomata remain closed, the plant cannot take in CO2 and photosynthesis is disrupted.
Kaolin application not only reduces heat stress in plants, but is also effective in preventing sunburn and preserving fruit quality.
Figure 2. Temperature Change Taken with a Thermal Camera. a) Fruit with and without kaolin application. b) Kaolin applied fruit surface temperature is 28.2 °C, fruit surface temperature without kaolin is 48.2 °C (Glenn et al. 2002)
Kaolin can be easily applied with the equipment used by producers and there is no need for any other equipment. It forms a thin white layer on the plant surface after application. Another effect of kaolin application is the fight against pests. The plant covered with kaolin becomes visually and tactilely different for pests and reduces insect damage with the “host camouflage” effect. Many harmful fungi and bacteria require a direct contact surface with the leaf surface. Kaolin application prevents direct contact of water and spores with the leaf surface and contributes to the suppression of possible infection in the plant. In order for the kaolin application to continue its effectiveness, it is necessary to repeat the kaolin coating washed off with rain and various applications made from the leaf as the plant develops (coating of new shoots and leaves).
Prof. Dr. Murat Ali TURAN
REFERENCES
Glenn, D. M., Puterka, G. J., Drake, S. R., Unruh, T. R., Knight, A. L., Baherle, P., Baugher, T. A., 2001. Particle film application influences apple leaf physiology, fruit yield, and fruit quality. Journal of the American Society for Horticultural Science, 126(2), 175-181.
Glenn, D.M., Prado, E., Erez, A., McFerson, J.R., Puterka, G.J., 2002. A reflective, processed kaolin particle film affects fruit temperature, radiation reflection, and solar injury in apple. J. Am. Soc. Hortic. Sci. 127, 188–193.
Glenn, D.M. G.J. Puterka, 2005. Particle films: A new technology for agriculture. HortRev.31:1–44.
Lombardini, L., Harris, M. K., Glenn, D. M., 2005. Effects of particle film application on leaf gas exchange, water relations, nut yield, and insect populations in mature pecan trees. Hort Science, 40(5), 1376-1380.
Rosati, A., Metcalf, S. G., Buchner, R. P., Fulton, A. E., Lampinen, B. D., 2006. Effects of kaolin application on light absorption and distribution, radiation use efficiency and photosynthesis of almond and walnut canopies. Annals of botany, 99(2), 255-263.
Shellie, K. C., King, B. A., 2013. Kaolin particle film and water deficit influence red wine grape color under high solar radiation in an arid climate. American journal of enology and viticulture.