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Boron Deficiency in Soybeans

Boron is essential for all plant growth. Soybeans, like all legumes, have a high boron requirement. Boron is necessary for:

  • Stimulation of root growth
  • Increased root nodule development for nitrogen fixation
  • Increased branching and flowering
  • Increased bloom retention
  • Increased number of pods
  • Better seed development and grain yield

Soybeans are considered to be non-responsive to boron. And, soybeans appear to be sensitive to boron toxicity, especially when the boron is applied to the leaves. However, yield reductions do not necessarily accompany leaf spotting and marginal necrosis caused by excessive boron accumulation.

What does boron deficiency look like?

As with many plants, the earliest sign of boron deficiency occurs in the roots. The root tips die and new roots are initiated giving a rosette appearance.

Likewise, the death of the shoot growing point is followed by prolific development of lateral shoots with brittle petioles.

The right boron fertilizer

Boron fertilization of soybeans has been shown to increase grain yield at many locations in several states. University researchers have found yield increases ranging from 5 to 18 bushels per acre.

Field studies conducted by the MS Foundation (Dr. Douglas Gitti) in Maracaju, Mato Grosso do Sul, Brazil, during the 2016-17 crop, demonstrated that Granubor® 2 provided a higher yield gain in the soybean crop when compared to granulated ulexite applied equivalently in-furrow.

The same research group found that during the 2017-18 harvest Granubor 2 provided a gain of 6.4 sacks/ha of soybeans in comparison to the control when applied in a pre-sowing dose of 7 kg/ha (1 kg/ha of boron). There were better climatic conditions for soybean cultivation during the 2017-18 crop compared to the 2016-17 crop.

How much boron is enough?

Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue tests. Never apply boron in direct contact with the seed.

Timing your boron application

  • Boron may be applied in dry or fluid blends. With dry bulk blend fertilizer, broadcasting before planting is recommended, using Granubor 2.
  • Boron in liquid suspensions may be applied broadcast before planting, banded at planting, or sidedressed, using Fertibor® in suspensions.
  • Boron in liquid fertilizers may be broadcast before planting, banded at planting, sidedressed, or fertigated using Solubor®. This material may also be mixed with pesticides or applied to foliage in aqueous spray.*
*Foliar sprays should not exceed 0.5 lbs/acre boron per application.
*Fertigation allows timely split applications of boron when it is needed by the crop and minimizes leaching. Drip-trickle fertigation allows incremental applications of 0.1 to 0.25 lbs/acre boron through the drip system.
*The total amount of boron added in foliar sprays or split applications should not exceed the total broadcast recommendations.

Soil Application (Suggested rates of application)

  Granubor 2 Fertibor
LBS./ACRE 3-6 3-6
KG/HA 3.38 - 6.75 3.38 - 6.75

Foliar Application (Suggested rates of application)

LBS./ACRE 2.4-5
KG/HA 2.7 - 5.625

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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