boran

Very little in general. Boron occurs in very small amounts in soil - less than 1 part per million so you have to be very cautious in trying to correct it. The balance is upset by excess of the major minerals - such as you can get when too much nitrogen and calcium are used . Sometimes the use of uncomposted manures creates this. You could try a proprietary mix of trace elements or try this. Mix a quarter level teaspoon of borax with a half gallon of water for using over an area 5 square feet. Use acidic mulches.