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Bring on the boron

Boron deficiency can cause failure to set seed and ergot infection

In both wheat and barley, boron deficiency causes the unfertilized cereal grain flowers to open up just like open pollinated rye. The consequences of deficiencies are failure to set seed, as in canola and wheat, and, in barley, the open, exposed cereal flowers can have very high levels of ergot.

Over the last few years in the Prairies, there has been something of a resurgence of interest in boron. This micronutrient is critical for normal plant growth, particularly crop maturity, and water balance — and is a key factor in seed set and crop yield. In man and animals, this micronutrient is essential for weight gain and proper bone formation.

Boron is generally present in most Prairie soils and is usually adequate in soils high in organic matter but can be low to deficient in sandy or coarse silt soils. In the soil organic fraction, boron is released during cultivation along with nitrogen and sulphur, but only in very small amounts.

Boron is seldom deficient in clay soils, especially those high in organic matter. In sandy soils, leaching may occur and boron can be washed out of such soils or moved below the crop root zones. Boron, like sulphates and nitrates, is a very leachable mineral.

Soil tests for boron should be at least 0.5 to one part per million (ppm) in all crop soils, whereas in clays, silts and muck soils, boron should be in the one to two ppm range. In other words, one pound per acre is considered low but two to four pounds of boron per acre is considered optimal. Never overdo boron fertilizing since in-furrow applications can be seed toxic and soils that have more than 10 ppm of boron can be toxic to grain crops.

Have you noticed the soils next to a saline slough are areas in the field that will grow canola but not barley? That’s because in these saline areas, boron soil levels can range from 10 to 50 ppm of this mineral and canola is much more tolerant than barley.

Boron toxicity is a primary reason why crops, particularly barley and wheat, grow poorly or die out in low, saline spots in croplands.

Boron can kill ants, but do not throw it on an anthill on the lawn, or it will kill the grass. Put it in a waterproof container mixed with sugar. Boron, Borax or Borateem are, or were, readily available in grocery stores as a laundry additive. Not so many years back, so much boron was used in wash water that the city of Edmonton had a problem with its compost. I was able to show the city the compost they used had 25 to 50 ppm of boron, enough to kill off its summer annual flower beds where they applied this compost.

Some of you older folk, like me, can remember the days when there were TV commercials staring Ronald Reagan when he was the actor/spokesperson for 20 Mule Team Borax, which was mined in Death Valley, Calif.

One of the problems with soil available boron is when soils dry out and the crop roots move down the profile, particularly in canola, the subsoil may have no boron and the surface six to 12 inches (15 to 30 centimetres) is too dry for the canola crop to pick up needed boron. This micronutrient is also non-mobile in the plant, so it cannot move to where it’s needed.

The consequence of this lack of boron is failure to seed set. What happens? Boron catalyzes the movement of pollen in all plants from pollination to the time the pollen grain (the male) makes its way down to the ovary, where it fuses with the female ovum to initiate seed set. Therefore, no boron or deficient boron means reduced or no seed set if the soil is either deficient in boron or it has become very dry (i.e. very dry soil conditions restricting boron uptake by the crop).

In British Columbia, where boron can be very deficient in cereals (wheat, barley and oats), there may be very poor seed set.

In Quebec and Ontario, it’s not uncommon to have soils in some areas that are less than 0.1 ppm soil available boron. What happens in Quebec is not only will there be a great yield reduction in barley, but also lots of ergot infection.

Boron deficiency consequences

Boron is the mineral that is absolutely essential for guidance in the pollen tube to fertilize the ovary. In the absence, or deficiency, of boron, pollination will fail in crops such as barley and wheat.

What are the consequences of boron deficiency? Failure to set seed and ergot infection. In both wheat and barley, boron deficiency causes the unfertilized cereal grain flowers to open up just like open pollinated rye. The consequences of deficiencies are failure to set seed, as in canola and wheat, and, in barley, the open, exposed cereal flowers can have very high levels of ergot.

Yes, Virginia, this work showing reduced grain yield and ergot infection was done in Finland in 1981 by a P. Simojoki and later by Denis Pageau in Quebec in the 1990s. Pageau was able to vastly increase barley yields and eliminate ergot by applying a few pounds of boron per acre to boron-deficient soils.

To sum up this situation, a deficiency or lack of boron causes pollen tube failure and a lack or deficiency of copper causes pollen sterility. Both mineral deficiencies result in ergot infection in cereal grains.

Boron, again like copper, plays a significant role in stem lignification, influencing crop standability.

Boron fertilizer exists as powders, prills, granular forms and liquids. Sodium borate and Solubor have the highest concentrations, at around 20 per cent boron. It takes five pounds of either form to add one pound of boron per acre for a value of 0.5 ppm. Boron levels, like those of other micronutrients, should be checked every year or so to avoid significant crop yield losses, which could be prevented by a crop micronutrient supplement.

In the many papers and texts written by soil scientists or agrologists, there hasn’t been a mention of boron deficiency in wheat or barley. This information was published some 30 to 50 years previously, but totally overlooked.

About the author

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Dr. Ieuan Evans is a forensic plant pathologist based in Edmonton, Alta. He can be reached at [email protected]

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