ABSTRACT
The importance of boron (B) as an essential micronutrient for plant growth was discovered in 1923 by Katherine Warington of Oxford, United Kingdom (Marschner 1995). Boron’s value was first uncovered for legumes, and later for nonleguminous plants, by A. L. Sommer and C. B. Lipman of the University of California (Epstein and Bloom 2005). Boron is present as undissociated boric acid, or B(OH)3, in soil solutions at pH values less than 7; it disassociates to B(OH)4− only at higher pH values. Boron is the only micronutrient present over a wide pH range as a neutral molecule rather than as an ion (Epstein and Bloom 2005) and is the only nonmetal among the micronutrient elements.
