Cooperative Extension Pomology Nut Crop Advisor David Doll showed growers some positive results from kaolin clay research. Doll says the idea is very basic as the product simply keeps the tree from getting as warm as it normally would from sunlight. He says this is another tool for growers during low chill years.
More About the Research
From The Almond Doctor blog: In attempts to increase chill unit accumulation in the winter of 2014-2015, several applications of Kaolin clay (Surround®) were made to a ‘Kerman’ with ‘Peters’ pistachio orchard located near Coalinga, CA. Seven rows were randomly selected and sprayed, and the remainder of the orchard was left untreated. The first application was made on January 10th, 2015 with 40 lbs/acre of Surround® applied by ground rig. Follow up applications were made after rains on January 23rd and February 10th, 2015. Data loggers were installed in four trees, two data-loggers per treatment, with three sensors per tree on February 6th, 2015. Sensors in untreated and treated trees were 100 feet apart. Temperature sensors were wrapped around the wood in order to measure the temperature of the wood with one sensor in the northeast and southwest quadrant of the tree, while the third measured ambient air temperature. Upon data logger removal, chill portions were calculated by taking hourly temperature data and using this available spreadsheet. At harvest (September 15th, 2015), clusters were counter per tree and individual tree harvest were taken. Ten randomly selected trees in each treatment were measured for the paired study.
The kaolin treated trees were found to have a higher cluster count and yield. Kaolin trees had an average of 50.4 clusters and 2.004 lbs per tree, while untreated trees averaged 21.0 clusters and 0.015 lbs per tree. Blanking was considerably higher in the untreated trees. Temperature information collected from the data loggers found an increase in chill portions between the period of February 6th and 20th, 2015. Over this two week period, kaolin coated trees accumulated one more chill portion than the untreated trees and ambient air temperature. Furthermore, kaolin coated trees leafed out and bloomed 14-20 days after untreated trees during March/April, 2015. Read more from The Almond Doctor.