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Why did my cereal crop lodge?

Practical Research: Was it disease? Too much nitrogen? Or was it a copper deficiency in your soil?

This year, 2018, was the year of the lodged crop on the Canadian Prairies. Back in early September, the weather turned cold and much of the Prairies were covered repeatedly with heavy wet snow. In the northern half of the Prairies up to 80 per cent of the crops were yet to be harvested. Fortunately, three weeks of warm, windy weather in the latter part of October allowed much harvesting to be completed despite the widespread crop lodging.

This year’s heavy and unusually early snowfalls in September and early October were unavoidable and destructive of crop quality.

Aside from wet snowfalls, severe windstorms and driving rains, crop lodging can be effectively avoided in many instances through crop fertility and management.

Lodging in crops like canola and sunflowers can be caused by diseases such as sclerotinia white mould. In peas, by a lack of support tendrils and such causes as temporary flooding and of course windstorms and snow as we saw this year.

In small grain cereals there is a lot of folklore and mythology about crop lodging which generally focuses on the fable of “too much nitrogen.”

I read several publications and articles on the role of nitrogen put out by the Prairie provinces’ provincial governments, but none made any factual sense. There were zero answers as to why nitrogen was the cause of lodging, no facts just opinions and waffle.

Sandy soil and cattle manure

There is also the fairy tale of sandy soil and cattle manure.

So, you apply 10 tons of cattle manure in the fall to your sandy cropland quarter that produced only 30 bushels of canola that year, because you have heard that manure is good for sandy soil, especially for water holding and release of nutrients.

You reckon that you should seed to spring wheat and expect a 40- to 60-bushel crop at harvest. You have been told at the coffee shop that cattle manure is a good source of nitrogen. Many manures may have excessive straw or even wood shavings. Wheat straw has an 80:1 carbon (C) to nitrogen (N) ratio; good cattle manure can be 20:1 or even up to 40:1 C to N ratio. Just because you were told that cattle manure has 10 to 12 pounds of nitrogen per ton, doesn’t mean that you have applied 120 pounds of nitrogen to your wheat crop, not counting the two per cent organic fraction of the sandy soil. in most years this cattle manure will only release perhaps 35 per cent of its nitrogen, not the whole 120 lbs.

Thus:

  • 10 tons of cattle manure with lots of straw has about 120 pounds of N.
  • Release of N in the first year from this manure is about 35 per cent, giving up 40 pounds of nitrogen.
  • The two per cent of the organic fraction of the sandy soil at best will give up 20 pounds of N.

Conclusion: You now have just over 60 pounds of available N, even if your phosphate, potash and sulphur are adequate. The previous 30-bushel canola straw will release additional N but only 10 pounds at best. Your total is now 70 pounds of available N.

What sort of wheat yield do you get? Probably around 40 bushels of wheat and your whole crop lodged to boot.

What did the coffee shop crowd tell you? Your crop lodged because of too much nitrogen

That answer is speculative nonsense.

What likely happened is that the ten tons of manure provides a huge source of carbohydrate (straw) energy — good for the soil fungi, bacteria and other biological life. These micro and macro-organisms all need micronutrients such as copper, which is in short supply (deficient), and is denied to the wheat crop. As a consequence, the wheat crop becomes super deficient in copper and lodges. The wheat may also show melanosis (browning) and the presence of ergots, further proof of severe copper deficiency.

Other evidence

Am I alone in this factual account? No not by a long way. I can quote from Horst Marschner, one of the most eminent of soil scientists, in his text book Mineral Nutrition of Higher Plants:

  • “Impaired lignification of cell walls is the most typical anatomical change induced by copper deficiency.” Lignification is the process that strengthens the plant’s body.
  • “An increase in the lodging susceptibility of cereals.”
  • “a decrease in lignification occurs even with mild copper deficiency.”
  • “Lignification responds rapidly to copper supply.”

There are at least two copper enzymes in lignin biosynthesis. Smell the coffee please! We have removed about a half ounce of copper (15 grams) from every acre every time we remove grain, hay or cattle annually from our croplands. So, if you have been farming this land for 100 to 300 years do the math on copper removed. Over 100 years you have removed 50 ounces of copper which amounts to about three pounds per acre. How much copper was there to begin with in the top six inches of soil? Just a few pounds on average. Sandy or light, loamy soils are the first to run out of copper. Peaty soils also sequester (tie-up) copper.

Why do we supplement the diet of every pig, poultry, sheep, cow, horse or bison with copper? It’s because the amount of Cu in prairie feedstock is too low to meet their needs. Has the “penny” dropped yet?

Copper and lodging

When you look at a partially lodged field why does the cereal crop lodge in the low spots but not on the higher, better drained spots? Wind does not do this. Its due to the fact that in the lower spots there is better moisture and shallow rooting. In the dryer areas the cereal roots go deeper and pick up sufficient copper several feet down. In the low spots the cereal roots stay shallow and end up in the top six to 12 inches that has become copper deficient. In years of drought we see very little cereal crop lodging. That is because the roots have to move deep into the subsoil for moisture and pick up adequate copper.

The next time that you see a lodged crop of wheat or barley, go to the turns or low spots and pick up some plants. The stems have not bent or broken, they just buckled like a piece of rope that you tried to stand up. Lack of lignification is due to a lack of copper and the result is lodging. We used to aim for 30 bushels of wheat now its 120 bushels, four times the yield which needs four times as much copper. Do the math.

Many growers create an imbalance of nitrogen, another factor that increases the lodging susceptibility, by interfering with copper metabolism and stem strength and lignin formation. It’s the lignin produced by copper-based enzymes that makes all cereal crop stems firm and resistant to lodging.

Creating an imbalance

Soil tests calculate the amount of N, P, K and S required to produce a 70-bushel crop of wheat or a 100-bushel crop of barley.

The problem is that the N and S (sulphate) requirements are easily calculated but the P and K (phosphorus and potassium) are another matter. If the crop requires 30 pounds of P and perhaps 60 pounds of K remember that both these fertilizers are only partially available to the cereal crops in the years of application, perhaps only 15 to 20 per cent at most. What often happens is that the P in particular is still deficient as perhaps is the K, but the N and S are fully available.

What results is a surplus of N (too much nitrogen) and too little P and K. This N surplus, coupled with the soil-available N, is unbalanced and can interfere with copper uptake and metabolism in the plant. This results in poor lignification of the cereal stems, resulting in crop lodging.

So, if you have frequent problems with crop lodging not related to unbalanced N or weather factors try a few acres of copper application, particularly if you farm sandy soil, peatland or soil high in organic matter.

Herbicides, especially Group 1s (fops), can cause severe lodging of wheat especially, if the cropland is low or deficient in copper. When you see wheat standing in the wheel tracks following herbicide application and lodging in the rest of the field you have a prime example of herbicide interference in wheat stem lignification. During herbicide application, the wheels crush the wheat seedlings, resulting in a much-reduced uptake of herbicide by the wheat seedlings in the wheel tracks. The lower levels of herbicide in these seedlings are not enough to interfere with the copper-based enzymes that form lignin and give the wheat plants good stem strength. The herbicide is telling you that your crop is low-to-deficient in copper

I would suggest that if you have frequent crop lodging on the Prairies that you apply some 40 pounds of bluestone (use a Valmar spreader) to about five to 10 acres of your problem fields — that’s about 10 pounds of actual copper. You will get cereal crop standability significantly increased or absent, increased yields and an absence of ergots. That copper application of 10 pounds per acre is good for 15 to 20 years or more. You will get your money back and more in cereal yield and quality in just a couple of years.

In summation, I can categorically say that I have provided you with a definitive and factual cause of crop lodging in cereals. I am dealing with facts, not fictional opinions that are all too common in agriculture circles, often by so-called experts.

Remember, in the land of the blind the one-eyed man or woman is king or queen.

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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