Deciding which cover crops to use

There’s more known now about what cover crops work in what soils and for what end uses

Radish-based cover crops are becoming less common as farmers look to fix more nitrogen with legumes.
Reading Time: 3 minutes

Planting cover crops following winter wheat harvest is not a new concept for Ontario producers.

The ability of cover crops to add organic matter to soil, sequester weeds and reduce erosion is greatly beneficial but one cover crop won’t work for all producers and their needs.

“It’s going to depend on the grower, their situation, their soil type, their concerns or challenges with weeds or other issues,” says Jake Munroe, field crops soil management specialist with OMAFRA.

Why it matters: There are many different cover crops, so deciding which to use can be overwhelming.

Soil type

When looking at soil types some crops work better than others.

For clay soils, especially growers new to growing cover crops, varieties that die over winter and have low biomass are best.

“Someone brand new into it, having to manage a cover crop like rye in the spring on heavy clays – the window of opportunity for spraying and planting is tight,” says Monroe.

As well, it’s important growers don’t go too high on the cover crop seeding rate, and it’s best they use a moderate size cover crop.

“You know what that residue looks like come spring. A concern for farmers on clay is soil drying and warming. Start small and moderate to learn the growth and thickness of that cover crop.”

Oats, peas or radish are great starting points for those farming heavy clay soils.

Loam soils provide endless options, especially with the opportunity to overwinter, says Munroe “If they are well drained, I can’t think of a cover crop that would not be a good option for a loam soil.”

When looking at sandy soils, it depends if nitrate leaching is a concern.

“(If it is), cereal rye or even an oat and radish mix after wheat is best to help suck up any extra nitrogen in the biomass.

As well, having a bit extra residue or biomass from that cover crop is ideal.”

Soil issues

If growers are using cover crops to help with erosion, the best option depends on whether they are looking at wind or water erosion.

“The more mass on top of the ground will help to prevent the soil from being picked up. With water erosion you want to have more root system underneath the ground to hold the soil,” says Wayne DeBoer with General Seed Company.

Fall rye is known to hold water well. Brassicas with wide leaves prevent soil loss from wind erosion.

When growers are looking to add organic matter, diverse mixes are the best option, says DeBoer.

“It’s not the pounds you plant, it’s the diversity of items. The more diversity, the more they compete against each other; the plants get bigger and they bush out more,” says DeBoer.

Diversity is beneficial, but being able to manage all those different cover crops is important.

“When we have too diverse of a mix there’s sometimes too many things going on. Species that are flowering too early and setting seeds will cause all kind of volunteer issues the next year,” says Munroe.

Both Munroe and DeBoer have said they notice a continuous increase in the use of cover crops.

DeBoer says there is a specific increase in the use of legumes over the past few years with radishes being less common than before.

“People are looking for cover crops that fix nitrogen so their fertilizer input costs the year after are a lot less.”

It’s important growers match cover crop type to what they plant in that field in the next season, and what their goals are with the cover crop. Will it be tilled down? Will it be planted into? Will it be grazed? As well, DeBoer says it’s important to add nitrogen to get the cover crop off to a good start.

“(Those) who understand that you have to feed a cover crop to get it started, have tremendous results. If you expect the cover crop to grow on it’s own without any nutrient value to start off with, the cover crop is not going to do well.”

About the author


Jennifer Glenney

Jennifer is a farm reporter who lives in Cayuga, Ontario.



Stories from our other publications