{Malus sylvestris}

Boron Deficiency in Apples

Boron is an essential nutrient for all plants. Fertilizing apple trees with adequate boron is necessary for:

  • Flower formation
  • Fruit development
  • Tree growth

Boron deficiency commonly causes cracking and external cork symptoms on the fruit. This may occur even though the foliage shows no symptoms, such as rosetting of thickened brittle leaves and dieback of the growing points. Boron deficiency causes premature fruit drop, and fruit quality can be badly impaired by the cork formation. If the internal cork develops early in the season, the affected fruit will become badly deformed.

In severe cases, dead areas appear in the bark of young branches (apple measles). The bark may be rough and cracked. Boron deficiency may affect the movement of calcium from the tree leaves to other tissues. As a result, boron deficiency often is associated with "bitter pit."

Applying boron fertilizers has been shown to increase yields and improve the quality of a wide variety of crops. Apples respond well to the correct amount of fertilizers. However, applying too much boron to apples can cause toxicity, so soil testing and leaf analysis is critical to determine the extent of boron deficiency.

Spotting Boron Deficiency in Apples

U.S. Borax Products for Apple Trees

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 7-21 7-21
KG/HA 7.88 - 23.63 7.88 - 23.63

Foliar Application (Suggested rates of application)

LBS/ACRE 2.5-5
KG/HA 2.8 - 5.6
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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