Submitted to: International Horticultural Congress
Publication Type: Abstract only
Publication Acceptance Date: 5/20/2010
Publication Date: 8/22/2010
Citation: Glenn, D.M., Kim, S. 2010. High residue amounts of kaolin further increase photosynthesis and fruit color in 'Empire' apple [abstract]. International Horticultural Congress. Interpretive Summary:
Technical Abstract: Kaolin (Surround WP, NovaSource, Phoenix, AZ, USA) is commonly used to reduce sunburn damage in fruit crops and to reduce heat stress on foliage. It is typically applied at rates of 3% to 6%, resulting in leaf and fruit residue levels of 1-3 g/m2. Crop modeling of the effect of kaolin on leaf/canopy temperature and diffusion of light within the canopy, due to the reflective particle film, indicated that photosynthesis may be further increased by higher kaolin residue levels. A 5-year field study in which 0%, 3%, and 12% Surround WP were applied bi-weekly to fully mature ‘Empire’ apple trees was conducted in Kearneysville, WV. The 12% application level deposited 5-7 g/m2 of residue on the leaves. Canopy photosynthesis was increased by 3% Surround and further increased by 12% Surround. Fruit mass was increased by 3% and 12% Surround in 4 of 5 years in non-irrigated treatments and in 2 of 5 years in irrigated treatments. Fruit color was increased over the control in all years, and in 2 of 5 years, the 12% Surround had improved red color over both the 0% and 3% Surround treatments. Soil gas exchange studies demonstrated that the 12% Surround treatment had greater root/soil respiration in the spring of 2009 than the 0% and 3% treatments, suggesting that the increased photosynthate was partitioned to the root system. These data support crop modeling results that indicate increased value of reducing canopy temperature and increasing light diffusion within tree canopies.