Boron [B, 5]

Boron, a metalloid of the group 13 in the periodic table of elements, occurs in the Earth’s crust at an average amount of 10 mg/kg. Boron is widely distributed in the hydrosphere, and its water solubility highly controls its distribution in the environment. Boron contents in soils vary between 10 and 100 mg/kg, being enriched in calcisols. Boron movement in soils follows the water flux, and thus in cool humid-zone soils, it is leached downward in soil profiles, whereas in warm-zone soils, and especially in arid and semiarid regions, it is likely to be enriched in the surface soil layers. Boron is an essential element for plant growth and its biochemical role is still under investigation. Boron interacts in the uptake of other nutrients by plants because it has an influence on the membrane permeability and cell colloids.