Boron Application

Application Options

Boron can be applied directly to soil, through fertigation, or as a foliar spray. Because boron application rates are quite low, uniform coverage is difficult to achieve when distributing by hand. The best option is usually to combine boron with other fertilizers. Doing so can help to decrease application costs and provide more even coverage. (Application as a seed treatment is not recommended.)

As a soil amendment

Granular boron (2-4mm, such as Granubor®) can be directly applied to soil and can also be bulk blended with other nutrients to provide specific boron rates, depending on crop needs. Read more about Granubor's distribution rate in bulk blended fertilizers.

Boron works well as part of fluid fertilizers—assuming you use high-quality boron that is free from insoluble contaminants.

Refined boron can be used to add boron to compounded NPK fertilizers, usually by dissolving or suspending the boron in phosphoric acid or mixing with a solid component of the fertilizer before granulation. Known as “boronated fertilizer,” this type of product is an excellent way to incorporate boron with a fertilizer regime. 

As a foliar spray

Foliar sprays (such as Solubor®) are an excellent means of applying boron to tree, nut, and vegetable crops. Uniformity is easy to achieve, response is nearly immediate, and application rates can be lower. Be sure to use high-quality product and best practices for application or you might risk leaf burn. Foliar spray is NOT the best option for young plants that lack sufficient leaf surface.

Read more about the amount of Solubor to mix into spray tanks.

In fertigation

Boron can be distributed through inclusion in field or drip irrigation systems. This method demands careful measurement and system calibration to ensure the desired rate of application.

Recommended Boron Rates

Application rates vary depending on crop, soil type, irrigation, and yield goals.
Soil texture Range of soil test boron Boron fertilizer requirement
Sand and loamy sand < 0.2 ppm All crops
Sandy loam, loam, silt loam, and silt 0.2 - 0.5 ppm Medium and high boron-requiring crops
Clay 0.5 - 1.0 ppm Medium and high boron-requiring crops
Clay 1.0 - 2.0 ppm High boron-requiring crops
All soils > 2.0 ppm None

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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