No abstract

Application of a kaolin-based particle film, Surround WP, was analyzed using glass plates and slides. The kaolin was sprayed on coffee grown in full sun to evaluate physiological responses to this shading technique. Kaolin reduced photosynthetically active radiation and ultraviolet transmission and decreased surface temperatures on glass slides. In the second year of application, photosynthesis of plants sprayed with kaolin was 71% greater than full-sun plants and yields were doubled. Leaf temperature was significantly lower in the kaolin treatment, but stable C isotope ratios, water use efficiency, nodal growth, and specific leaf area were not. The most likely mechanisms for increased yield are increased light transmittance to inner-canopy nodes or greater storage of photosynthate during the first year. Although results from this study suggest there is much promise for improving the performance and yield of coffee with kaolin application, studies with other species have shown inconsistent results. This inconsistency may be linked to variation in application techniques, kaolin coverage and subsequent effects on light transmission, leaf temperature, and physiological function. Thus, reports on physiological performance alone are insufficient to evaluate the use of kaolin application. Detailed information on application techniques combined with measurements of end-product criteria such as yield or quality are recommended to facilitate cross-study comparisons.