Boron Application for Avocados
Hello, I am consulting for a family friend who has an Avocado farm in Mexico. His tissue tests show that across the board his trees are deficient in Boron. They average tissue concentrations of B around 15ppm, where the ideal range is 30-60ppm. I know Boron is mobile and potentially toxic if over-applied, but from my research it appears that soil drenches of small amounts of Boron (Borax or boric acid solutions) show positive results in nutrient uptake in Avocados, and that Avocados are nearly 10x more tolerant to Boron toxicity than other plants. My question is this: How do I figure out how much Boron needs to be added to each tree to avoid creating a toxic soil environment? I've seen a recommendation for a solution of 0.75 ounces of Borax (11% B) to 100 gallons of water from Cornell, but I don't know how much of that solution would be applied to each plant. They claim that supplies 6 ppm B. If the client's avocado trees are deficient by about 15-40ppm in their tissue, how do I know how much of that solution needs to be applied to the soil of each tree without creating soil toxicity but also being effective? I figure multiple small applications with more tissue sampling will help us narrow it down, but I'd like to reduce the number of tests necessary to get the right application. I also want to know why I've recommended the amount I have when the time comes. The trees are mature and flowering. If you can help me I would greatly appreciate it!
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