Chapters 5.23

5.23 -Adopting the use of antitranspirants on plant seedlings to combat drought in Africa: kaolin clay

Sonam Jinpa-Perello, University of Guelph, Canada

Suggested citation for this chapter.

Jinpa-Perello,S. (2022) Adopting the use of antitranspirants on plant seedlings to combat drought in Africa: kaolin clay, In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

What is transpiration and why do antitranspirants help with drought

Transpiration is the loss of water from plants through their surfaces (such as leaves, stems, and flowers) in the form of vapour. Transpiration can cause plants to lose up to 99% of the water absorbed through their roots (Koteswara Rao et al., 2018). In a drought, yield can be reduced drastically depending on the severity and length. Periodic drought for 10 – 15 days at an early or late stage is expected when farmers lack irrigation systems, but drought during the critical growth phases such as flowering and grain development is highly detrimental. The severity of intermittent drought lasting 6-10 days during critical stages of a crop can reasonably be avoided by the use of antitranspirants (TNAU, 2013 ).

There are four types of antitranspirants, but the reflectance type, such as kaolin clay, will be the focus of this paper. Kaolin clay is primarily made up of kaolinite. Kaolinite is chemically stable, non-toxic. Kaolinite deposits can be found in areas where there are rocks rich in aluminum silicate minerals, such as feldspar (Nelson, 2014). In general, the reflectance type of antitranspirant works by coating the plant with a solution, which then reduces leaf temperatures by adding a layer of protection from the sun. This is how kaolin works, as kaolin’s effectiveness is due to the white protective particle coating that is formed on the plants surface from the application. This protective film increases the reflection of excess radiation, which then results in the reduction of leaf and fruit transpiration (Brito, Dinis, Moutinho-Pereira & Correia, 2019). Some experiments have shown that reflective antitransprants diminished transpiration rates up to 22-28% and also reduced leaf temperatures by 3-4 degrees Celsius after one coating of kaolinite clay (Hagan and Davenport, 1970). Other reflective antitranspirants include, but are not limited to, lime water and calcium bicarbonate (Koteswara Rao et al., 2018).

Kaolin clay also has multiple other uses: it can also serve as an insect repellent for plants and can be mined in certain areas as a source of income. Kaolin clay is an effective insect repellent, because while it has been found to be an ineffective immediate insecticide, it can discourage insects from interacting with plants coated kaolin as it makes the plant unrecognizable. Also, the insect can be severely impacted by the attachment of the clay particles to their body as they crawl on the plant, which could impair them enough that they will eventually die (Glenn et al., 1999). In the case of mining kaolin in Africa, most kaolin deposits and occurrences are located in southwestern Africa, because kaolinite clay is found to mostly occur in soils that have formed from the weathering of rocks in hot, moist climates (Nelson, 2014). Within Africa, there are over 292 deposits recorded. The market for kaolin has strong economic potential in the continent as there is increasing local and international demand (Ekosse, 2010).

Target Crops and Countries

This practice is applicable in many different countries and on a variety of crops, given the versatility of the product. Attention should be paid to the cost of transportation and availability of the resource when considering implementing this practice.

Details (Specific to Kaolin Clay)Instructions

The supplies required to implement this practice are: kaolin clay, water, a pump sprayer and liquid soap, though the liquid soap is optional, but recommended (Novasource LLC, "Surround WP Kaolin Clay, Application"). When using kaolin clay for plants, it must be mixed thoroughly and applied through a sprayer and coated onto the plants liberally in the mixture (Grant, 2018). When considering this in general terms, the kaolin clay spray should be applied to crops every 7 to 21 days for at least four weeks, and insect control against pests should occur within three applications as long as a sufficient and uniform spray has been achieved (Grant, 2018).

The clay powder should be mixed with water at a rate of three cups of powder per one gallon of water. The water should be gradually stirred into the clay to reduce clumping, as opposed to mixing all at once (Plant Care Today, 2019). To further reduce clumping, shake the sprayer occasionally during the application, if possible (Novasource LLC, "Surround WP Kaolin Clay, Application"). It is important to note that for sprayers difficult to shake, farmers should premix the ingredients in a bucket and then pour the mixture into the sprayer.

Labour and implementation

Adopting the practice of applying antitranspirants does increase the amount of labour inputted by the farmers; depending on the resources available to them, the amount of additional labour needed will differ. The sprayers can be mechanized, and additional tools like whisks can be used to improve the process of combining the clay and water. Antitranspirants do require certain environmental conditions during application to get the best results. This can be divided into two categories to consider: type of crop and weather conditions:

conditions: For best results, apply on a still, overcast day. Wind can cause uneven coating and wasting of the mixture. Harsh sunlight, if the mixture is not thoroughly mixed, can increase the risk of burning the plants if the water pools after the application. Do not apply if there is a chance of rain, as the kaolin clay mixture will wash off. The liquid requires conditions that allow it to dry evenly on the surface of the plants (Plant Care Today, 2019).

Type of crop: As stated earlier, antitranspirants can be used on a variety of different crops to mitigate heat stress. The frequency and rate of application will depend on specific environmental conditions, the coverage of the spray achieved, the crop’s growth stage and rate, which are at the discretion of the farmer to monitor. Ideally, spraying of antitranspirants will occur before water and heat stresses occur, and consistent coverage on all plant surfaces during the periods of high heat and light exposure should be maintained. For example, most corn, melons and rice are estimated to need around 25-100 lbs of kaolin per acre of crop, and the application should be 1 to 2 times each season, or as needed. For root and tuber vegetables, it is estimated that only 25-50 lbs will be needed per acre, with the application being 1 to 2 times per season, or as needed (Novasource LLC, n.d.).

Conflicts

When considering whether to apply reflective antitranspirants onto crops, there are various internal and plant-specific factors to take into consideration. There are three types of transpiration: lenticular transpiration, cuticular transpiration, and stomatal transpiration. Stomatal transpiration is the cause of the majority of water loss in plants, and while reflective antitranspirants help ease the stress, they should be seen as short term aid as opposed to a permanent solution (Koteswara Rao et al., 2018).

There are some significant constraints to consider when considering adopting antitranspirants into real-life agricultural practices, as they will be different from the studies conducted, a few of which being “the inability to maintaining control over the microclimatic conditions, their effect being varied greatly with the inputs chosen and environmental factors, it can be difficult to cover the entire leaf surface of some crop plants and not receiving proper application of the substance could reduce the effectiveness, the lack of knowledge on the type of nozzles and surfactant to be used, and the cost of certain chemicals forbids their use as antitranspirants” (Koteswara Rao et al., 2018). No consensus has been reached regarding its effectiveness as a whole as there have not been enough studies on different crops and under different stress intensities (Brito, Dinis, Moutinho-Pereira & Correia, 2019). Although, there have been studies that found snap bean plants treated with kaolin were able to withstand drought for 6 days, while the plants treated with other antitranspirants were only able to withstand 5 days (AbdAllah, Mashaheet, Zobel, & Burkey, 2019).

Storage and transportation issues

There are a few potential issues to consider when thinking about adopting antitranspirants into rural farm agriculture. For example, antitranspirants should be stored in a ventilated dry area. There is also the added issue of shipping and transportation if not purchased locally. Many sellers online of Kaolin clay, the more feasible option, are located in China, despite Kaolin being a resource found in Africa. It will not be uncommon to find that there is also a minimum order of at least 1 ton, which poses the opportunity to then collaborate with local partners when ordering but also poses the same risk. Implementation of this practice by a single smallholder farm would be difficult without community support.

Safety issues

There are circumstances in terms of health and safety that should be kept in mind when applying antitranspirants. While kaolin clay is classified as non-toxic, it can be uncomfortable to get into one’s eyes or lungs, which could occur when being handled, and therefore protective gear would ideally be worn. If the mixture is sprayed directly onto fruit/vegetables, they should be washed with clean water prior to eating, which can be difficult when considering clean water scarcity (Grant, 2018). Additionally, it has been found that a coating of kaolin dust can make it difficult to judge whether the fruit is ready to harvest (Plant Care Today, 2019).

Links to Additional Resources

1.https://www.youtube.com/watch?v=oKGNIMec048 Applying kaolin powder to tomatoes.

2.https://www.youtube.com/watch?v=7XlDfSx8A-Q Using kaolin clay as a pesticide for apple trees

3. https://www.youtube.com/watch?v=ipQ6xlmP9EQ&feature=youtu.be Discussion, basics on kaolin from a western farmer.

4. https://www.youtube.com/watch?v=ct2J5qHLpHk Discussion on the types of pre-made antitranspirants and the benefits (Wiltpruf and Vacation are brands mainly discussed)

5. https://plantcaretoday.com/kaolin-clay.html A website that covers points on the implementation of using reflective antitranspirants.

6. https://www.alibaba.com/showroom/kaolin-clay-powder-for-agriculture.html An online website where tools and kaolin can be purchased.

7. http://www.fao.org/3/y3655e/y3655e03.htm An article posed by the FAO on deficit irrigation scheduling based on plant growth stages and water stress tolerance.

References

1. AbdAllah, A. M., Mashaheet, A. M., Zobel, R., & Burkey, K. O. (2019). Physiological basis a. for controlling water consumption by two snap beans genotypes using different anti b. transpirants. Agricultural Water Management, 214, 17-27. c. doi:10.1016/j.agwat.2018.12.029

2. Brito, C., Dinis, L., Moutinho-Pereira, J., & Correia, C. (2019). Kaolin, an emerging tool to a. alleviate the effects of abiotic stresses on crop performance. Scientia Horticulturae, b. 250, 310-316. doi: 10.1016/j.scienta.2019.02.070

3. Brillante, L., Belfiore, N., Gaiotti, F., Lovat, L., Sansone, L., Poni, S., & Tomasi, D. (2016). a. Comparing Kaolin and Pinolene to Improve Sustainable Grapevine Production during b. Drought. Plos One, 11(6): e015663. doi: 10.1371/journal.pone.0156631

4. De, R., Bhujanga Rao, D., Yogeswara Rao, Y., Giri Rao, L., & Ikramullah, M. (1983). a. Modification of irrigation requirement of wheat through mulching and foliar application of transpiration suppressants. Irrigation Science, 4(3), 215-223. doi: 10.1007/bf00285527

5. Ekosse, G. E. (2010). Kaolin deposits and occurrences in africa: Geology, mineralogy and a. utilization. Applied Clay Science, doi:10.1016/j.clay.2010.08.00

6. Grant, A. (2018, April 5). What Is Kaolin Clay: Tips On Using Kaolin Clay In The Garden. a. Retrieved from b. https://www.gardeningknowhow.com/plant-problems/pests/pesticides/kaolin-clay-insect-control.htm.

7. Glenn, D., Puterka, G., vanderZwet, T., Byers, R., & Feldhake, C. (1999). Hydrophobic a. Particle Films: A New Paradigm for Suppression of Arthropod Pests and Plant Diseases. Journal Of Economic Entomology, 92(4), 759-771. doi: 10.1093/jee/92.4.759

8. Hagan, R. M., & Davenport, D. C. (1970). Part I: Potential Usefulness of Antitranspirants a. for Increasing Water Use Efficiency in Plants. Part I: Potential Usefulness of b. Antitranspirants for Increasing Water Use Efficiency in Plants(pp. 13–36). of Water c. Science and Engineering, University of California, Davis. Retrieved from d. https://escholarship.org/content/qt3wd852m8/qt3wd852m8.pdf

9. Koteswara Rao, G., Surendra Babu, M., Sravani, V. and Sindhuja, M. (2018). A Review a. On-Influence of Antitranspirants (ATs) in Vegetable crops. International Journal of Pure & Applied Bioscience, [online] 6(3), pp.394-399. Available at: http://www.ijpab.com/form/2018%20Volume%206,%20speissue%203/IJPAB-SPE-2018-6-3-394-399.pdf [Accessed 30 Sep. 2019].

10. Nelson, S. (2014) ENS 2110: Weathering & Clay Minerals. [online lesson]. Retrieved from a. https://www.tulane.edu/~sanelson/eens211/weathering&clayminerals.htm

11. Novasource LLC. (n.d.). Surround WP Kaolin Clay, application. Retrieved September 30, a. 2019, from b. https://greenearthagandturf.com/products/pest-insect-control/surround-wp-kaolin-clay/.

12. Plant Care Today. (2019). Kaolin Clay: Tips On Using Kaolin Clay For Organic Garden a. Insect Control. [online] Available at: https://plantcaretoday.com/kaolin-clay.html [Accessed 29 . 2019].

13. TNAU. (2013). TNAU Agritech Portal: Agriculture. Tamil Nadu Agricultural University, a. Coimbatore, India. Retrieved 5 November 2019, from b. http://agritech.tnau.ac.in/agriculture/agri_drought_management.html

14. Team Agri Info. (2017, June 6). Antitranspirants. My Agriculture Information Bank. a. Retrieved from https://agriinfo.in/antitranspirants-435/