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Supplementing with Borates: What Are You REALLY Putting into Your Soil?

:: Friday, July 28, 2017 :: Posted By Fabiano Silvestrin
For decades, farmers and food growers across the world have been aware of the benefits they get from supplementing their soil and plants with boron. Growers who do not supplement their crops with boron are often left with less-than-optimal yields. 

Although all boron comes from natural sources, not all boron products are the same, and they don’t all produce optimal results. To understand why some types of boron perform better than others, it is important to understand the differences between the two types of borates available for agricultural use: raw borates and refined boron. 

Sources of Boron

Boron is found in many raw industrially important borate minerals, such as tincal, kernite, ulexite, and colemanite. Although boron makes up a significant amount in all of these, the presence of other elements within these borates heavily influences their ability to serve as boron supplements for soil and crops. 

Tincal and kernite are sodium borates and can be found in the U.S. Borax mine in Boron, California. Tincal and kernite are ideal borates since they do not contain calcium, an element that reduces water solubility. Since water solubility is critical to boron uptake by plants, anything that reduces the water solubility will ultimately limit the yield of overall crop production. 

In addition, the presence of calcium in some raw borates makes it harder to isolate the boron within the minerals because calcium affects the absorption of boron, which makes it a less available source of boron for plants. For example, ulexite is a calcium-sodium borate and colemanite is a calcium borate.  

Why Refined Boron Matters

The distinction between sodium borates and calcium-sodium borates isn’t limited to just their composition. Refining is a deliberate process that removes impurities and creates a highly stable and consistent product. 

The first step in the refinement process is dissolving the minerals and then settling the dissolved liquor to separate borates from unwanted mud and contaminants. Then the borate slurry is re-crystalized, and the crystals are washed, filtered, and dried. The resulting dry borate crystals are:
  • Free from contaminants such as arsenic, which can stunt plant growth and affect yields
  • Higher quality through better process control
  • Consistent in size and concentration, resulting in better performance in the field
  • Fully soluble in water, improving availability for plants in sprayed applications

Return on Investment

When you apply raw minerals, application tends to be uneven, uptake is inconsistent, and results are variable. In addition, the inconsistency of raw minerals means that you don’t get full availability of the product you apply. Most estimates indicate that boron availability in a raw product averages between 20-40% over a 20 week period. That means that for every 100 pounds of product, at best you get only the approximate benefit of 40 pounds.1

With high quality refined products such as those from U.S. Borax, you get 100% availability—so you use less, get better value, and more consistent results.


1 T. Broschat Horttechnology July-September 2008 18(3), RTM internal studies

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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 500 customers with more than 1,700 delivery locations globally. We supply 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles east of Los Angeles.  Learn more about Rio Tinto

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