Wheat School: Wheat's role in building soil fertility and health

Across Ontario, a growing percentage of soil tests are testing lower for nutrients. It’s a trend growers need to be aware of, and there’s a role for wheat to play in addressing the decline.

Jack Legg, SGS Agri-Food Laboratories agronomist based at Guelph, says his lab and the International Plant Nutrition Institute, which conducts sampling surveys every four to five years, have both observed the declining pattern.

At the annual C&M Seeds Industry Day last month, Legg told growers he’s seeing more samples testing below the critical level, which means crops are relying on fertilizer inputs to achieve optimum yield levels as opposed to the soil feeding the crop.

When it comes to the macro nutrients, Legg says potassium and phosphorus are the big decliners. But micronutrients are also hitting the radar. For example, he notes several reports of copper deficiency in 2019. “That’s almost unheard of in Ontario,” says Legg. After 200 years of growing crops in this province, “we’re eventually going to get below the soil supply,” he adds. “We can’t keep taking money out of the bank without putting in a deposit from time to time.”

On this episode of the RealAgriculture Wheat School, Legg also discusses how growers can make up for higher nutrient removal rates driven by increasing crop yields. Overall, he believes growers are doing a good job managing their soils, but there are some nutrient facts they need to factor into their soil management plans. One is the widely-held notion that soybeans don’t need fertilizer. In reality, soybeans are nutrient hogs, requiring 1.5 lb of potassium per bushel. “A 60-bushel crop is taking out 90 pounds of potassium fertilizer and growers are not putting that much on a soybean crop,” says Legg. (Story continues after the video.)

Legg also discusses the state of soil organic matter in the province and the role wheat can play in building organic matter, which is also showing a declining trend.

Legg says he doesn’t want to raise alarm bells, but he believes growers should be looking for opportunities to work wheat into their rotation. He understands that wheat has to be economical for farmers, and some years it can be tough to build a business case for the crop, but the long-term value of wheat is indisputable.  He notes long-term rotation work by Dave Hooker at Ridgetown College, University of Guelph, which shows how wheat can significantly increase corn and soybean yields when it’s part of the rotation.

Unlike soybeans, wheat is also a big contributor to organic matter and soil health. “It adds a different plant to the system and by having different roots and residues, it also helps increase the soil biological life,” says Legg. He notes that wheat secretes glues, gums and waxes that really help build soil structure. Those sticky substances keep soil well-adhered and gives it a better aggregate stability.

Click here for more Wheat School episodes.

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