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Getting the most out of cover crops

Soil organic matter decline is long-standing issue on farms across the country. The more widespread adoption of cover crops, however, is helping to reverse the trend.

With the right management strategy, cover crops can boost biodiversity, growing conditions, and overall soil health.

Jake Munroe, field crop soil fertility specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs, says farmers can plant different cover crops to accomplish different goals. Those new to cover cropping can start slowly by incorporating a single-species that doesn’t overwinter into their rotation.

Different crops for different needs

If banking nitrogen is the goal, for example, legumes might be the best option. Reducing erosion might require species that develop more biomass. Compaction prevention could start with crops producing large, fibrous root systems such as cereal rye.

Henry Denotter, a grain farmer from Ontario’s far southwest, says he tried a diverse array of cover crop species. One of his most significant issues with growing them in his heavy clay soil is getting the ground uniformly dry and warm before spring planting.

In his experience, the most effective way to ensure good soil conditions at planting is to terminate in autumn.

“I like to spray early,” he says, and adds that he prefers crops – like oats – that can be easily killed with glyphosate. This is because glyphosate does not leave a residue in the soil, meaning he is not limited in what he can plant afterwards.

Kris McNaughton, research associate at the University of Guelph’s Campus in Ridgetown, reiterates that getting the right herbicide formulation is critically important.

Plan ahead

Most single species cover can be eradicated with one or a mixture of two herbicides, she says. The diversity of cover crop blends, though, means developing a herbicide prescription requires more care.

“You really need to know what you’re going to plant,” says McNaughton when referring to both cover and subsequent cash crop.

“Roundup should definitely be put on at the two-litre rate. You need something that kills but doesn’t leave a residue. Maybe put in a group one to kill grasses, plus a group four. You should be watching for escapes anyway.”

Blake Vince, another grain farmer from southwestern Ontario, says incorporating cover crops doesn’t require new, expensive equipment either.

Vince has been planting 18-species cover crop mixtures after winter wheat in a no-till system since 2011. Grain crops the following spring are planted into the green cover left by overwintering species. This is done using a standard seed drill with some modifications to help it cut through cover crop residue.

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