Cover crops. How can farmers sow for success?

by Arlene Barclay | Jun 6, 2024

Cover crops are picking up steam. But with a number to choose from, each with their own distinct benefits, choosing which is best isn’t always easy. Here, we explore what cover crops are, why you should plant them, and how farmers can succeed with them.

What are cover crops?

Cover crops are plants sown intentionally to keep the ground covered and improve the physical, chemical, and biological character of the soil. They differ from cash crops, which are those sold solely for profit, e.g. corn or wheat.

The primary job of cover crops is to improve the soil. They’re often planted in fields that would otherwise be bare, for example between growing seasons.

The benefits of cover crops

Cover crops provide many benefits for farmers. They keep the soil covered and maintain living roots on the farm. This helps prevent erosion and improves soil structure, which is important for flood and drought resilience.

They also help smother weeds, control pests and diseases, enhance water availability, can reduce synthetic input dependence, and increase biodiversity on the farm.

According to Herberto Brunk, manager of Herdade das Escravides de Baixo, the benefits of cover crops are endless.

“Cover crops will soon become your most important crop. If you’re doing arable, they will dictate your cash crops establishment and likely your yield. If done right, they do everything from sequestering large amounts of carbon to restoring your soil biology.”

— Herberto Brunk

Why should you plant them?

Every time you grow a cash crop, the plants extract nutrients from the soil. Those nutrients need to be returned so the next cash crop can succeed.

Many farmers use fertilisers and chemical herbicides to return those nutrients and suppress weeds. But some cover crops are able to fix nutrients like nitrogen naturally. As such, many farmers are now taking synthetic inputs out of their tool box and replacing them with cover crops.

Leaving residues from your cover crops on the field is also a great way of increasing the amount of carbon in your soil. This means you could improve the health of your farm and access a new income stream from carbon+ credits.

Take the case of a 50 ha irrigated arable farm: If you sow a winter cover crop mix in October and leave 3.5 tons of residues on the field in February, you’d receive around 5.740€. A good deal for a bare field.

How to grow cover crops successfully

When it comes to cover crops, context is everything. The species selected should align with your objectives, soil-type, climate and production model.

One thing that rings true is that like in nature, diversity is key. Multi-species cover cropping allows farmers to tap into the benefits of each plant and effectively reach one – or multiple – goals.

For example, many farmers combine legumes, grasses, and a flowering plant for biomass production, biodiversity, nitrogen fixation, weed management, and soil erosion prevention.

“Doing cover crops all starts with your context. It depends on your production model and what you’re trying to achieve, whether that’s soil microbiology, nutrient cycling, water retention, compaction issues, and so on. If you’re not considering these things, you’re pretty much just growing weeds.”

— Herberto Brunk

Types of cover crops

There are many different classes of cover crops, including: legumes (such as alfalfa or clover), grasses (such as ryegrass or barley), brassicas (such as radish) and a number of flowering plants (such as buckwheat or sunflower).

Legumes

are a farmers favourite. They’re celebrated for their ability to fix nitrogen in the soil due to their symbiotic relationship with rhizobium bacteria. They’re also a highly effective weed supressor.

Grasses

are higher in carbon that legumes, so when they break down in the soil the residues often last longer. This is highly beneficial for suppressing weeds and increasing soil organic matter. Grasses are also effective scavengers, meaning they absborb excess nutrients left in the soil from the previous crop.

Brassicas

offer some distinct benefits. They provide a lot of biomass. But they also have naturally occurring pest management properties, meaning they’re able to release chemical compounds that are toxic to pests and soil pathogens.

 

Flowering plants

are a great way to attract beneficial insects and pollinators to your farm. The more biodiversity you have, the more the farm takes care of itself.

Using cover crops to increase your bottom-line

As is often the case in agriculture, it’s good to keep in mind your bottom-line when assessing whether to implement new practices. Cover crops are an investment. But the reduced input costs could outweigh the costs of seeds and machinery greatly.

People are succeeding with it, too. As Farmers Weekly reports, Rick Clarke, a farmer in the U.S, has saved approximately £ 1.6 million on his 3.000 hectare farm through organic no-till. His approach to regenerative farming is underpinned by a solid multi-species cover crop system, as well as no-till and no chemical inputs. He emphasises that striking the right balance is challenging, but not impossible.

According to Herberto, the biggest challenge with cover crops is understanding your farm context. He states that it will likely take you down a rabbithole at first, but when you establish the right mix of seeds for your goals, it feels like a great alliance.

Rick Clark’s annual savings on his 3,000-hectare farm

Diesel

£50,936

Nitrogen

£489,414

Phosphate

£270,189

Potash

£280,705

Lime

£101,927

Agrochemicals

£390,722

Seed

£84,939

 

Diesel

Nitrogen

Phosphate

Potash

Lime

Agrochemicals

Seed

£50,936

£489,414

£270,189

£280,705

£101,927

£390,722

£84,939

Source: Farmers Weekly: ‘Organic no-till system saves US grower £1.6m in costs annually’

Closing remarks

Having living roots in your soil year round is key to building resilience from the ground up.
But cover crops offer a lot of other opportunities for farmers, too. Whether it be reducing your input costs or accessing a new income stream from carbon+ credits, they’re an effective way of improving your soil and your bottom-line.