Photosynthesis and Establishment Rates of Southwestern Pecan Orchards Treated with Foliar Kaolin Particle Film (Surround® WP)

The purpose of this study is to evaluate whether kaolin particle film increases leaf net carbon assimilation, growth and establishment rates of immature ‘Western’ pecan (Carya illinoinensis) trees grown under hot, high light intensity, low relative humidity conditions of southern New Mexico. In 2009, canopies of trees in two orchards, one in its first-leaf and the other in its second-leaf, were sprayed with a kaolin particle (Surround^® WP) suspension eleven times from early May through early October, at approximately 3 week intervals. Net carbon assimilation rates of fully sun-exposed leaves measured mid-season, July 15, 2009, on kaolin particle film-treated second-leaf trees were 47.8% higher than that of untreated control trees during the 1000-1200 HR time period but did not differ significantly from the control earlier or later in the day. At the end of the 2009 growing season there were no statistically significant differences in trunk diameter, total current-season shoot length or percentage fruiting terminals for the first- or second-leaf trees.  In 2010, kaolin particle film treatment was continued for a second year on the trees that were first-leaf in 2009.  No significant differences in leaf net carbon assimilation rates were measured during the 2010 growing season on second-leaf trees and, even after two full consecutive seasons of particle film treatment, no statistical differences were found in trunk diameter.