Boron Quality Matters

The value of refined boron

Damien Slowik Technical Development Specialist

Get a snapshot of boron’s importance to plant health and how refined boron can help improve crop yield. Learn More

Applying boron?
Quality is more important than quantity.

Boron is a naturally occurring mineral. But refinement and quality control are necessary to provide a source that can
  • Mix well with other nutrients
  • Dissolve completely in liquid applications
  • Enable uniform application
  • Provide maximum availability to crops
Subpar products might cost less up front, but high-quality refined boron is cost competitive when evaluated on a price-per-useable-kilogram basis.

“Solubility is key to the farmers who are going to use it out in the field and want a steady, constant release of boron. Our refined sodium borate is able to deliver that over the entire growing season.”

Mark Manning | Principal Scientist, U.S. Borax
Mark Manning | Principal Scientist, U.S. Borax

Low-quality boron can do more harm than good 

Not all borate products produce the same quality or level of useable boron. When it comes to boron, product price is not always the best measure of true return on investment (ROI). A less expensive product can end up costing more over the long term if you need to purchase and apply more of it or if it does more harm than good.

Only high-quality, highly available, refined boron has a long-lasting, significant, positive effect on crop yield.



U.S. Borax refined borates are sourced from one location: our Boron, California mine. The boron in this deposit comes primarily from tincal and kernite, which are calcium-free sodium borates

Why does this fact matter? Because excess calcium can cause boron-deficiency symptoms in plants. 
Borates that contain colemanite or ulexite—calcium-borate minerals found in many raw or lower-quality boron products—often contain high levels of calcium, even after refinement. The difference is clear—literally.


Other impurities, such as arsenic, also compromise the quality of some borate products. Our studies of fertilizer samples  show arsenic content of as much as 157 ppm in samples of Turkish 10% boron ore, while Chilean 10% boron ore can contain as much as 1,500 ppm. By comparison, U.S. Borax refined Granubor® 2 contains less than 5 ppm.

Boron (B) Ore Sources
  • Analysis of fertilizer samples
  • Product consistency is variable
Supplier   Water Solubility B CaO Arsenic content (ppm)
Turkish 15% B 5.4% 19% 141
Turkish 15% B 5.4% 0% <20
Turkish 14% B 4.7% 0% 151
Turkish 10% B 7.4% 21% 157
Chilean 10% B granular 5.2% 22% 1500
Peru 10% B granular 5.9% 12% 962
Granubor 2   15.5% 0% <5
Granubor 2   14.9% 0% <5


Refined products with high solubility offer more available boron per application than do unrefined borates that fail to fully dissolve. Borate minerals that are only partially soluble are more difficult for plants to use, provide patchy coverage, and often leave insoluble contaminants behind in the field.

Granulated ulexite is a sodium-calcium borate product that is only partially water soluble and therefore not as available to crops.

Granubor 2Ulexite
%B Average 14.3%Inconsistent B levels
Particle Size
Water Solubility 100% solubleIncomplete dissolution
Research > 30 years of worldwide field tests and researchLimited field tests
Purity No added ingredients, fillers, or coatingsCan contain high levels of Arsenic, Aluminum, and Barium

Refined boron delivers better results and environmental assurance

Paul Fink Regional Sales Manager

The U.S. Borax refinement process produces consistently superior, high-performance, and OMRI Listed® products—day in and day out. Watch video

The Refined Borates Advantage Is in the Purification Process

U.S. Borax products such as Granubor 2, Fertibor®, and Solubor® are fully refined to remove impurities and maximize potential uptake. This process results in a pure, natural product that provides optimized nutrition throughout the growing season.

The U.S. Borax refining process involves several important steps:
  • We mine high-quality sodium-borate ore that is naturally low in calcium and other contaminants.
  • We dissolve the ore in water.
  • We settle the dissolved borate liquor to remove impurities.
  • We cool the liquor and then further wash and filter the resulting crystal slurry.
  • We dry the refined slurry to produce dry borate crystals.
  • We check our products for purity, solubility, consistency, and optimal granulation.
  • We constantly conduct and review field tests and other research to improve our products and services.
Each of our products is designed to meet a different need, learn more.

Production Process of Refined Borates at U.S. Borax 

Crude Ulexite Ore from Other Borate Providers

Most other borates go through only minimal (if any) processing. These products are merely washed, dried and calcinated, and granulated. As a result, they are typically less soluble, contain more contaminants, are inconsistently sized, and provide less reliable boron availability rates than refined boron.


Boron sources are not equal

Research shows that not all boron sources are equal in their ability to provide plants with soluble boron throughout the season.

Various Sources of Boron
  • Hot water test (HWT) results on various B sources
  • All samples similar particle size

Questions to ask when selecting boron

As you can see, the best way to measure the value of a boron supplement is to look beyond the initial price point. Low-quality, unrefined products can quickly eat up any cost savings by being ineffective—or actually creating new problems. When you evaluate products, be sure to ask about the real value of the borate you’re buying:
  • How much useable, water-soluble boron does the product contain?
  • Has the product been refined to remove contaminants such as arsenic, lithium, and aluminum?
  • Does the product support multiple types of application?
  • What is the product’s bulk density?
  • Can the product make boron available throughout the growing season? 
  • Is the product durable (e.g., crush resistant during transport)?
  • What is the typical particle size (for granulated boron products)? 
  • What is the price per useable measure of boron?

Returning to refined boron: Central America

Customer Success Story Oil Palm

A U.S. Borax customer who decided to switch to nonrefined mineral borates sees a real difference in crop yield. Watch video

Find the best product for your specific needs

Learn more about refined U.S. Borax products and how they can provide maximum ROI and higher crop yields than lower-quality products.

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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