{Gossypium spp.}

Boron Deficiency in Cotton

Boron has been universally recognized as the most important micronutrient for cotton production. It is essential at all stages of plant growth, and critically so during fruit development—especially with today’s fast-fruiting, high-yielding varieties. University research shows that as little as 1 lb of boron can increase seed cotton yield by more than 500 lbs per acre.

Boron is an essential element that cotton needs during all stages of growth and fruiting. Supplying adequate boron will help cotton:

  • Develop and retain more squares
  • Increase bloom pollination and boll set
  • Move nutrients and sugars from leaves to the fruit
  • Produce strong, well-developed fibers
  • Speed maturity

While severe symptoms of boron deficiency may not be found frequently, it is known that boron deficiency without the appearance of any visible foliage and flower symptoms can significantly limit the yield of seed cotton.

Apart from flower and boll shedding, a large number of symptoms on the leaves, petioles, flowers and bolls have been described. However, it is not expected that all the symptoms will be observed at the same time in any one field.

One of the more characteristic symptoms is the development of bands (often excessively hairy) on the petioles. The pith at such regions is characteristically necrotic. The terminal bud often dies and many lateral branches, which have short internodes and enlarged nodes, then develop. The leaves, which usually do not show any malformation, remain green until the first frost. In cases of extremely severe deficiency, excessive and abnormal vein development results in the buckling of the leaf and irregular leaf shapes.

The petals are frequently crumpled and misshapen. Excessive shedding of squares or young bolls occurs.

Discoloration of the extra-floral nectaries is common. Cracks may develop on the stems, at the base of the squares or bolls, and there may be some exudation.

How much boron is enough?

  • Since boron is essential for the transfer and assimilation of sugars and nitrogen into complex carbohydrates (fiber) and protein, demand for this element is greatest during lint and seed development. It is also during this time that boron is actually least available, in non-irrigated soils, because of dry conditions.
  • Cotton is especially vulnerable to boron deficiency during a drought that was preceded by heavy rainfall. And then again, after a drought is broken, when there is sudden flush of growth and fruiting—especially if nitrogen is plentiful.

Your boron fertilizer options

  • Granubor® 2 is an ideal material for dry blends that are applied broadcast preplant or sidedressed.
  • Fertibor® works best in fertilizer suspensions for preplant broadcasts, sidedressing or band sprayed over the pre-emergent seed row.
  • Solubor® allows you the most flexibility for applying boron. It can be dissolved alone in water or in liquid fertilizers and/or pesticides and then applied to the soil or directly onto the foliage.*

*Foliar sprays should not exceed 0.5 lbs/acre of boron per application.

Soil Application (Suggested rates of application)

  Granubor 2 Fertibor
LBS./ACRE 3-13 3-13
KG/HA 3.38 - 14.63 3.38 - 14.63

Foliar Application (Suggested rates of application)

KG/HA 2.25 - 10.125

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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