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Identifying copper deficiency in wheat

Ieuan Evans looks at 2019 growing conditions, including areas where copper levels are low

In early August in central Alberta I was still seeing yellow fields of canola. Honeybees and mosquitoes were having an extended nectar flowing season.

I will stick my neck out as usual and make a few observations and prophecies across the Western Prairies.

Crops are late in the northern part of the Western Prairies, but the canola crops look good and as a consequence of the rain they seem to have little in the way of sclerotinia stem rot. The continuous rain in this central area can drown out or wash down the aerial sclerotinia spores onto the soil surface and canola roots, unlike sunflowers and beans, are immune to sclerotinia root infection.

On a clear day in late July I flew from Edmonton to Winnipeg and trucked around Manitoba. The canola fields from west to east went from clear yellow to some yellow in Saskatchewan to green in Manitoba. Canola, corn and wheat crops looked surprisingly good from Winnipeg to Brandon despite the lack of substantial rainfall.

In the central and northern Prairies, the grazing pastures with 20 inches of rain or more in June and July are still green and lush. Hay crops were damaged by prolonged wetting and the lateness of the season caused many Edmonton area farmers to cut barley, oat and some wheat crops for greenfeed, fearing an early September frost and shortage of hay.

Potato growers in the Alberta central areas from Lacombe to Edmonton, particularly seed potato growers, can look forward to exceptional yields this year provided they have good September harvest conditions. Table and seed potato fields grown on a previous year’s fallow would typically run 15 to 18 tons per acre. With the heavy rainfall in June and July I expect to hear of many fields in the 20 ton per acre or more. Some potato fields have drowned-out areas due to the exceptional rainfall. The “Little Potato Company” is centered in the Edmonton area, but yields of six to nine tons are the expected for this North American-wide table product.

While everything these days is blamed on global warming, I can recall that the earliest killing frost just North of Edmonton occurred on August 11 on field peas around 1990, cutting short the ripening process. The latest frost in the central Alberta area occurred on July 10 damaging potatoes and many garden crops. The biggest fluctuation in a single week occurred late in August of 1994 when the Tuesday temperature went from 30 C to -5 C with snow in less than four days.

Lodging in wheat and barley

With this year’s heavy to excessive rainfall in June and July, we are seeing lots of grain lodging in central (northern) Saskatchewan and central Alberta. I saw field after field with flattened grain but some with good standing crops but somewhat late in maturity by early August. Now think and smell the coffee. Think! Didn’t you notice that the lodging in almost all fields was in the low spots and the turns? How come the grain, whether wheat or barley was standing on the higher and better-drained, windiest areas of the field?

Did you believe that this lodging was caused by wind and rain even in the best looking grain crops?

Did you examine the lodging for broken or bent over stems? You didn’t find any broken stems? It looked as though the cereal crop had sort of rolled over. The stems were, for the most part not bent badly they just rolled down.

How could the grain on the higher parts of the field and ridges still be standing despite the wind and rain?

Stem strength in cereals and all plants is dependent on lignin — not any magical dwarfing spray. What is lignin? Lignin is the complex carbohydrate that gives the wood in trees its strength. Without lignin the cereal stems are like pieces of rope — they just roll over and lodge.

Land in the prairies has been farmed for at least 100 to 200 years. Every crop that is removed or animal that grazes that land removes a few grams of copper (a half-ounce or so). Most cropland on the prairies only contained a few kilos of copper (two to three pounds) per acre, sandy soils even less in the top six inches. There is still lots of copper deep down the soil profile but when we get an abundance of rain, cereal roots stay in the top 15 centimetres (six inches) where the nutrients are — but the copper in this top 15 cm is missing. You haven’t replaced it. In the higher and sloped well-drained areas of your cropland, cereal roots go down deeper into the soil where there is still enough copper to form lignin and keep the cereal crop standing.

The inside of this field in the low-lying area is high in organic matter and very low or deficient in copper. The high organic matter sequesters or ties up what little copper that is left in the soil after about 100 years of crop removal. The severe lodging is not wind-driven. Note the standing wheat. Low or deficient copper results in severe lodging in wet years due to shallow rooting and the absence of copper. It also results in delayed maturity, ergot infection and missing grains in the wheat heads.
photo: Ieuan Evans

As growers, you might spend $20 to $40 per acre on pesticides. Why not, in some years, spend $40 an acre on about 10 acres of cropland where you have had lots of crop lodging in a wet year? The copper effect will last for 10 years or more.

In the field

Take a good look at these photographs that I took on August 15. Notice that on the edge of the wheat field the crop is standing and ripening. The rest of the low-lying part of the field shows severe lodging. How does this happen? The sandy loam field has been cultivated and cropped for over a hundred years. The ditch alongside the field was only formed about 15 years ago — the subsoil from the ditch a clay loam was piled onto the edges of the field. The subsoil contained good levels of copper and relatively low levels of organic matter — likely less than two per cent. The sandy loam in the field had five to six per cent organic matter.

Copper was available on the edge of the ditch, the wheat stood up and maturity was perhaps one to two weeks ahead of the rest of the field.

Conclusion, especially on sandy loams with wheat and barley crops lacking in copper in wet seasons:

  1. Severe lodging in wet years. Shallow roots.
  2. High probability of ergot.
  3. One to two weeks later in maturity.
  4. Significantly reduced grain yield and quality.

In dry seasons, even in sandy or clay soils the cereal roots will move down the soil profile 60 to 90 cm (two to three feet) where there will be adequate copper. This will result in little or no lodging, giving you earlier maturity, an absence of ergot and the expected target yield.

Wheat is very poor at extracting copper from the soil, barley a little better and oats are relatively efficient. Copper is vital for fertile pollen formation. Without enough copper, you will get pollen sterility and consequently, the normally closed flowers of these cereals will open in order for the female part (the stigma) to catch stray pollen. Instead of stray pollen, they may get ergot infection. You will never get ergot infection in wheat, barley or oats if they have adequate copper.

In dry years, the wheat fields would look like the gold maturing border since, in dry years, the wheat roots go deep into the soil — two to three feet, and pick up adequate copper. Please smell the coffee. We have had over 30 years of diagnosing this problem. There are many fields like this in the area, but also many fields in the area that have had three to five pounds per acre of copper applied recently that have very good-looking crops. If you have any alternative explanations please let us know.

Please, please do not pay heed to the fables that say, for example, ergot in wheat is due to cool wet weather and prolonged flowering. This type of statement comes from individual types who believe in fake news, a flat earth and Santa. Wheat, barley and oat flowers never open unless they are deficient in copper which causes pollen sterility, forcing the pollen-free cereal flowers to open and thus get ergot infection.

If you want to prevent or minimize lodging and avoid toxic ergot in your crops, pay attention to soil copper availability.

As a final footnote, rye is an open-flowered cereal and frequently gets infected with ergot. Triticale sometimes has open flowers and ergot infection can result. Check all grains on your farm for ergot as well as checking greenfeed and pasture hay for this toxic fungus that could well be prevalent this year.

About the author

Contributor

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

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