Refined Boron and Better Crops

Refined Boron vs. Raw Mineral Borates

Damien Slowik Technical Development Specialist

What is the difference between raw and refined boron sources—and in the end products and their effect on your crops? The answers might surprise you. Watch video

Refined Boron: A Building Block for Better Crops

Your crops rely on soil nutrients for essential health. Boron is a micronutrient that contributes to:
•    Strong cell walls and healthy cell division
•    Root, bud, and leaf growth
•    Sugar and calcium transport
•    Hormone regulation

Without optimal levels of boron available in the soil, crops become susceptible to leaf and stem damage, fruit drop or malformation, and impaired root growth.
 
Example of Boron Deficiency


Leaf deformation in coffee. Typical fan-like effect caused by the development of axillary branches after the death of the apical growing point. Some deformation of smaller leaves is also evident.

Boron also affects the levels of other nutrients (e.g., potassium, nitrogen, calcium) that are available for plant uptake.

Liebig’s Law of Minimums | A boron deficiency prevents absorption of essential macronutrients
Liebig’s Law of Minimums | A boron deficiency prevents absorption of essential macronutrients

How to Spot Boron Deficiency

Marcel Barbier Development Specialist

Understand the symptoms of boron deficiency and what the best practices are to identify the amount of boron in your soils and plants. Focusing on micronutrien... Learn More

How to Spot Boron Deficiency

Boron deficiency can be diagnosed via soil tests, plant symptoms, and plant tissue analysis.

Visual Symptoms
Boron deficiency in various crops shares certain characteristics including misshapen, thick, small, brittle leaves—typically affecting the youngest leaves first. 
 
Leaves
Misshapen, thick, small, brittle leaves—typically affecting the youngest leaves first
Stems
Short, shrunken stems and stunted or reduced growth points
Fruit
Cracked or watery tissue or fruit
Kernels
Malformed or irregular fruit or kernels 

Soil and Tissue Tests

Soil tests, such as hot-water extraction or Mehlich-1 or Mehlich-3 extraction, can help you determine whether plants have the right amount of boron available to them. Analysis of plant tissue samples can be used with soil tests to confirm boron levels in crops and can help to monitor levels as you begin to treat deficiencies.

Application Options

Boron can be applied directly to soil, through fertigation, or as a foliar spray. Because 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® 2) can be directly applied to soil and can also be bulk blended with other nutrients to provide specific boron rates, depending on crop needs. Boron works well as part of fluid fertilizers as well—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. Note that foliar spray is not the best option for young plants that lack sufficient leaf surface.
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.

Depending on soil type, an application of 4.4 pounds of boron/acre (4.93 kg/ha) can leach out of the soil within as little as 6 months.

Recommended Rates

Application rates vary depending on crop, soil type, irrigation, and yield goals.
 
Soil texture Range of soil test B B 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 B-requiring crops
Clay 0.5 - 1.0 ppm Medium and high B-requiring crops
Clay 1.0 - 2.0 ppm High B-requiring crops
All soils > 2.0 ppm None

Boosting Crop Health: North Dakota

Success Story Wheat

New applications of refined boron improved both yield and protein content in North Dakota wheat crops. As a result, growers were able to command more money pe... Watch video

Learn more about the benefits of boron-balanced soils

U.S. Borax has a wealth of knowledge about boron application and can recommend best practices. Explore our resources section to learn more.

Rio Tinto Borates is a global leader in the supply and science of borates - naturally-occurring minerals containing boron and other elements. Refined borates are essential nutrients for crops. We are 1,000 people serving 500 customers with over 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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