Identifying and addressing boron deficiencies in South America

:: Monday, August 22, 2022 :: Posted By Fabiano Silvestrin

Not only is boron a necessary nutrient for proper plant nutrition, but boron deficiency can significantly affect crop yields. This is especially prevalent in South America, particularly agriculture-rich Brazil, where most soils test at low levels of boron.

Weathered soils—with low pH and a low organic matter content—is a good indicator of low boron in soils. Following boron, zinc is the second most deficient micronutrient in Brazil’s soils.

Micronutrient deficiencies in Brazil

Illustrating the micronutrient deficiencies in Brazilian soil, this chart shows how 13,416 soil samples from 21 Brazilian states were collected and analyzed by the laboratory of the Institute Agronomic of Campinas (IAC).

Not all borates are created equal. Depending on the chemical refinement of a borate, the solubility and thus effectiveness and uptake availability differ. The source material and the interaction of boron with sodium, calcium, and magnesium all affect the solubility of boron. The more magnesium and calcium a borate has in its composition, the less soluble it will be as a mineral.

Solubility of borates

  • Hydroboracite (calcium and magnesium borate) Insoluble
  • Colemanite (calcium borate) poorly water soluble
  • Ulexite (calcium-sodium borate) partially water soluble
  • Kernite (sodium borate) water soluble
  • Tincal or borax (sodium borate) water soluble

Of these examples, only the last two undergo a refinement process to ensure they are the highest quality micronutrients and water-soluble, meaning the best source of boron will be able to fortify the plant more efficiently.

Solubility with different sources of borates

Unrefined borates (ulexites) release between 28 - 43% of the total boron content. Refined borates have greater solubility over 20 weeks, due to the absence of impurities and calcium in their composition.

Fortunately, U.S. Borax has created numerous products for a seamless boron application. This includes:

Additionally, there are other technologies in the works, including new liquid formulations.

Don’t starve your crops from boron. Work with your regional U.S. Borax representative to make a plan for balancing micronutrients in the soil.



U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 650 customers with more than 1,800 delivery locations globally. We supply around 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles. Learn more about Rio Tinto.

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