{Coffea arabica, C. canephora}

Boron Deficiency in Coffee

Coffee is one of the most susceptible crops to boron deficiency. In coffee cultivation, boron is necessary for:

  • Cell division and cell wall formation in interaction with calcium
  • Root growth and water uptake
  • Growth of internodes
  • Fruit size and setting
  • Calcium uptake
  • Decreasing aluminum toxicity
  • Drought and disease resistance

Boron deficiency causes the death of the terminal growing point. The later development of secondary branches (sometimes as many as seven at the same node) below the dead terminal bud has a typical fan-like effect. In severe cases, the secondary branches quickly die resulting in dieback of terminal sections of the new shoots.

In a study published in the Journal of Environmental Management, Muhammad Riaz, et al. demonstrated the importance of boron’s role in decreasing aluminum toxicity in citrus. Boron acted in the regulation of multiple physiological processes and has the potential to increase dry matter weight, plant height, root length, and number of leaves. This is applicable for coffee and other plant species.

Studies have also shown that with increased leaf boron content, there was a reduction in red mite infestation (Tetranychus pioroei). There was a correlation between boron and cyanidin production. Cyanidin is a polyphenol that is toxic to the mites. Another recent study showed that leaves with higher rates of boron concentration had lower rates of damage caused by coffee borer (Hypothenemus hampei).

What does boron deficiency look like?

When a plant is boron deficient, the leaves are typically misshapen and smaller in size. They are often narrow and twisted with irregular edges and have a leathery texture. The internodes are short, leaf tips may fail to develop properly, and the apical portion may then turn a pale olive/green color. In contrast, the basal portion of the leaf remains a deep dark green. It has been suggested that this apical chlorosis is due to a local calcium deficiency which may be the result of boron deficiency reducing calcium translocation.

Defoliation can occur. The underside of the midrib of both chlorotic and otherwise healthy older leaves may become suberized.

Production will be seriously reduced because of poor fruit formation. In nutrient solution studies, it has been demonstrated that boron deficiency does not seem to affect flowering but that, in contrast, fruiting is markedly reduced. In controlled experiments, no fruit was produced even though flowering was regular. This is in accord with work demonstrating that coffee shows a peak demand for boron (and for calcium) just after flowering and when the formed cherry is developing.

When do symptoms appear?

Terminal dieback and the development of crinkled leaves towards the end of a dry period and at the start of the rainy season (due to reduced boron absorption from the dry upper soil layers) are often the first signs that the coffee plant is suffering from boron deficiency.

Symptoms are also particularly noticeable at flowering and after liming due to the reduced availability of soil boron. Boron is mainly used on coffee to prevent the occurrence of the transient deficiency symptoms rather than to correct severe deficiencies which result in considerable branch dieback.

Spotting Boron Deficiency in Coffee

How much boron is enough?

Coffee removes significant amounts of boron from the soil each year (73 grams per ton of grain produced). Once a plant shows signs of deficiency it cannot fully recover. Flowering may be regular however there may be no fruit production due to lack of pollen tube development.

In soils containing more than 4% organic matter, boron may not be available to the plant because it can form complexes with diols contained in organic matter. In addition, affinity of organic matter for boron may affect boron uptake by plants due to changes in the boron concentration in the soil solution. Boron uptake by plants is controlled by the level of boron in the soil solution and by the total boron content in the soil.

Always consult your local department of agriculture or crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses obtained from young leaves found the terminal section of top branches.

Timing your boron application

  • High demanding periods for boron are after harvest, blooming, fruit setting, and fruit growth.
  • Boron should be applied to the soil alone or preferably blended with NPK and Mg.
    • With dry bulk blend fertilizer, broadcasting before initiation of floral bud is recommended, using Granubor®.
    • Boron in liquid fertilizers may be applied by fertigation using Solubor®.
    • Solubor may also be foliar applied just to amend when it is suspect that the uptake of boron through the roots could be disrupted. Application can be done during the spraying of insecticides or fungicides.

U.S. Borax Products

15% Boron |  | OMRI Certified
Optimum product for suspensions

A fine crystalline borate ideal for NPK compound fertilizers and suspensions. Manufactured as free-flowing granules, Fertibor is easily handled and offers superior flow and consistency.

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15% Boron |  | OMRI Certified
Made especially for bulk blenders

A pure, 100% water-soluble micronutrient that meets boron demand during the growing season. Made especially for bulk blenders, Granubor helps to ensure uniform distribution in nutritional blends and in the field.

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20.5% Boron |  | OMRI Certified
Product of choice for foliar applications

A concentrated, highly soluble, and fast dissolving powder that is ideal for foliar and other sprays. With the highest concentration of boron in any approved product, Solubor is an economical choice for nutritional formulations.

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20.8% Boron
Boron for fertilizer manufacturing

This refined U.S. Borax product is made from the dehydration and fusion of borax. Depending on the grade, Anhybor can be used to produce boron-enriched compound fertilizers or to coat different fertilizer products, such as NPK blends with the aid of a binder.

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10% Boron
Solubor Flow
For fertigation or hydroponic growing

First and only aqueous suspension of sodium borate microcrystals.

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14.5% Boron | 29% Zinc
Perfect combination of zinc and boron

Because zinc and boron deficiency are widespread around the world, a product with both nutrients is a good fit in many regions. Zincubor brings these two important micronutrients together in one product.

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Calculate Your ROI

Soil Application (Suggested rates of application)

  Granubor Fertibor
LBS/ACRE 9.0 - 12.5 9.0 - 12.5
KG/HA 10.0 - 14.0 10.0 - 14.0

Foliar Application (Suggested rates of application)

KG/HA 4.0
Value in Use
Current Yield (Per Acre)
Expected Sale Price

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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