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Cover crops’ role in soil health

In the second of our Great Cultivation Debate series, Mike Abram explores how cover crops change a rotation’s cultivations.

Cover crop mixes, such as those including linseed, can help a following cash crop to get its roots down quicker.
Cover crop mixes, such as those including linseed, can help a following cash crop to get its roots down quicker.

Soils have been long overdue the attention they have been getting in recent years and that focus is unlikely to disappear.

Not only are there agronomic benefits from improving soils, but Government policy is likely to drive further adoption of soil-friendly practices, with the arable soil standard among the initial eight standards in the pilot scheme of the Sustainable Farming Incentive (SFI) in England.

Martin Lines, UK chairman of the Nature Friendly Farming Network, says: “The early opportunity around SFI will be focused on soil.

“We are being encouraged to protect and enhance soils and that will include growing cover crops, not removing straw and other activities.” That is likely to mean further adoption of cover crops in rotations, but there can be plenty to learn about establishing them successfully and maximising benefits without impacting on the following cash crops.

Flexibility is important, says Mr Lines.

He has been growing cover crops in front of autumn and spring sown crops for the past five years, after originally gradually introducing them in places where he felt they would provide greatest value, usually ahead of spring crops.

 

Moisture

 

“We use the roots of the cover crops and the worms to be our cultivator.

We’ve found the soil becomes more workable, has less standing water after high rainfall and crops grow for longer as there is more moisture held in the structure of the soil.” Covers are direct drilled at an angle to how the combine went with a Kuhn Aurock direct drill.

“It has harrows on the back and we actively use them to disturb the tilth on top to get any weed seeds to germinate at the same time.” Ahead of autumn-sown cereals, the cover mix is usually fast-growing broad-leaved species, such as radishes, sunflowers, phacelia, spring vetches and buckwheat.

“You need to be flexible with what you put in depending on drilling date.

Every extra day in August is almost a week of extra growth.” Winter cereals are then drilled directly into the cover ‘into the green’ with the Aurock and the cover is sprayed off with glyphosate either just before or after drilling.

“You’re running on roots rather than bare soils, so you’re avoiding compaction.

We’re on heavy clay though, so if it is too wet, you’re best off not drilling.” The Aurock’s integrated crimper lays the cover crop down and helps with weed suppression in the first few weeks and reduces erosion risk from heavy rainfall, he says.

In front of spring broad-leaved crops, grass species covers are used, such as oats and rye, with radishes and some non-frost-tolerant species that die off and open the canopy.

Before spring cereals, a legume will be added.

For spring cereals, termination of the cover is at least six weeks before drilling to dry the land to drill, but also to remove black-grass.

“If you plant into black-grass, it robs yield from the following crop.

But with less soil disturbance, our weed burden is reducing, so my herbicide costs are dropping, with 62% lower fuel use costs.

So while the investment into the machine could be a factor, the overall benefit to the business and overheads is a lot better.

“I see the Kuhn Aurock as my Swiss Army knife because it gives me the flexibility to go into a cultivated crop, if necessary, or a metre-high cover crop and deal with both,” he says.


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Application and timing is crucial for cover crop destruction

Growing cover crops while managing significant populations of grass-weeds is not always an easy combination, suggests David Felce, Agrii regional technical adviser.

“In work we’ve done, we’ve generally found that cover crops per se will not cure black-grass.

If your key problem is black-grass, you can confuse the issue by having the cover crop in some ways, as you’ll want to leave the cover crops to maximise benefits, but also spray the black-grass.” In those situations, he suggests having a more open cover crop to encourage grassweed growth and then taking it out at least six weeks ahead of drilling a spring crop.

Choosing the correct dose of glyphosate for the situation is crucial.

 

“In more open canopies, 100 litres/ha is fine, but if you are trying to hit a small target a finer spray is better.”

 

“For small grass-weeds, 540g/ hectare is the bare minimum and as the weeds have started to harden off, move it up to the 720g/ha.

If you’ve got big cover crops at the other end of the scale, it’s probably more like 1,000g/ha of a product like Roundup Powermax.” Shading of grass-weeds can be an issue under bigger covers, he adds.

“In which case you might need two bites of the cherry – one to take out the cover and a second spray just ahead of drilling to take out the blackgrass that was underneath.” Attention to detail with application is also important.

“If you’ve got a dense canopy you need to get into that, so slowing down to 10-12kph and higher water volumes of 150-200 litres/ha can be very effective in helping to get better coverage.

“In more open canopies, 100 litres/ha is fine, but if you are trying to hit a small target a finer spray is better.”

How will machinery change to cope with cover crops?

How will machinery change to cope with cover crops?

Improvements to drills and add-ons to cultivation equipment are already being made that will help growers manage the establishment of cover crops and the following cash crops, says Ed Worts, arable product specialist with machinery manufacturer Kuhn.

Timeliness is an important consideration for establishing covers after harvest, with successful establishment as soon as possible key for maximum benefit.

Options available for establishing a cover crop include direct drilling into stubbles, the use of a stubble cultivator with a cover crop seeder attached, or broadcasting into the standing crop, suggests Mr Worts.

Broadcasting into the standing crop using an Aero GT with its wide boom spreader removes the need for cultivations and is likely to be most time-efficient, but might not be suitable for covers that establish best from being planted.

He adds: “Direct drilling, using something like our Aurock drill, is likely to give the best and most reliable establishment.

The limitation is it is a relatively slow process, typically about 10kph with a six-metre drilling width, whereas with a stubble cultivator with cover crop seeder fitted, you can be up around 15kph with a 9m working width.

“The stubble cultivator also generates a little bit of tilth, which will help the cover germinate, but when you’re working at very shallow depths you need a very accurate ground-following system to make sure that depth is maintained.

“To do that we’ve got Steady Control on our Optimer range, which is an active ground following system which monitors and maintains a constant pressure on the wings as the machine works to accurately control the working depth.” Similarly on Kuhn’s Aurock direct drill, innovation is also helping manage cover crops more effectively.

“It has a crimper integrated in front of the drill, which creases the cover crop stems, rather than completely cut them off.

That means it dies off more slowly and allows the seeds to grow through the crimped cover crop giving more protection to the growing plant, while retaining moisture.” In addition, the drill’s three hoppers and its ability to set coulters to different working depths allows more precise drilling of cover or companion crop seeds to optimum planting depths, he says.

The Great Cultivations Debate

The Great Cultivations Debate


Deciding on the most appropriate method of cultivation is currently one of the most debated topics in arable production.

 

The reality is there is no right or wrong answer. Numerous variables come into play when decision-making and there are pros and cons to all approaches.

 

This series will look at all aspects of the debate from machinery and engineering through to crop protection and nutrition.

 

 

Click here to read more

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