Cover crops. A practical farm example
The need to restore soil health, control blackgrass and reduce exposure to oilseed rape has resulted in a complete rethink over cropping and rotation on a North Yorkshire farm.
Twenty years ago half of the land at Stephen Tuer Farms was in grass for dairy cows. This provided a perfect three-year break for arable cropping, helping to condition soil and keeping pernicious weeds like blackgrass at bay.
We could plough out the grass and combination drill it the soil was teeming with life and we could get three good crops of wheat and barley before going back in to grass, says Steve Tuer.
When we gave up the dairy cows in 2009 we turned to break crops such as oilseed rape. We knew we were living off the inheritance of good soil biology, and that we probably had a 20-year honeymoon period before soil fertility would revert to that of an all-arable rotation.
To help maintain the soils biological fertility and structure, Mr Tuer has introduced several changes to his arable operation. He began by reducing the intensity of cultivations. Ploughing was largely replaced by tine-and-disc operations, which have become shallower over time.
In addition, he has more recently introduced cover cropping to boost his soils health, followed by spring crops to help control blackgrass. The weed has spread rapidly as a consequence of the all-arable operation and reduced cultivations.
We appreciate that blackgrass is a symptom of a bigger soil problem, says Mr Tuer. Growers further south have had to find solutions after theyve lost control. Im fortunate in that I can learn lessons and act while the chemistry set is still reasonably effective.
The cover cropping/spring cropping sequence required a leap of faith on the farms 400ha of heavy, high magnesium clays. The decision to adopt it was helped by the need to find suitable breaks to replace a large proportion of the oilseed rape.
This crop is no longer viable as the sole break crop following the loss of neonicotinoid seed dressings, a bitter blow for Mr Tuer, who held the unofficial world rape yield record just five years ago.
We couldnt continue with 100% winter cropping, because of blackgrass and because it didnt fit our strategy of trying to move less soil. So we decided it was time to think afresh and look at spring sowing.
Spring cropping on its own is a very high-risk strategy on the farms heavy soils. Its uncommon round here, says Mr Tuer. You cant just leave stubbles over winter and then expect to get a good seedbed.
Visiting Project Lamport
A visit to Agrovistas Project Lamport, recommended by the farms agronomist, Chris Martin, along with other events such as Groundswell, persuaded Mr Tuer to try a cover crop/spring crop sequence.
Chris is a fantastic sounding board and I very much rely on his expertise. I had also read the press and seen what other people were doing. I was convinced we had to try to move towards this sort of system.
Agrovistas work at Project Lamport has proved that the cover crop/spring sequence can work year in, year out even on very heavy land, says Mr Martin, who is also Agrovistas head of soil health.
We are trying to build resilience into the soil. Cover crops act as soil health improvers, returning organic matter to the soil, conditioning the soil with their roots and boosting soil biology.
Overwintered cover crops also draw out moisture through transpiration and improve drainage through rooting. This makes establishing profitable spring crops viable even on high-mag soils that Steve farms.
Healthier soils also help tip the balance in favour of the crop and away from blackgrass, which thrives in wet, poorly drained land. Using the right cover crop can help further.
Black oats grow slowly for a few weeks before entering their rapid growth phase, allowing blackgrass to germinate and establish. The young blackgrass plants are then sprayed off with the rest of the cover before the spring crop is direct drilled to minimise soil disturbance and the risk of fresh blackgrass chit.
Using these techniques, we reduced blackgrass plant numbers from 2000/sq m to single figures at Project Lamport over a couple of seasons, says Mr Martin.
Mr Tuer started cover cropping last summer, using black oats, phacelia and vetch ahead of spring barley and spring oats, and dropping the vetch where he intended to plant spring beans. A fifth of the cropped area, about 80ha, is now in this system, increasing this summer to around 140ha.
The spring crops were drilled with a demo Dale direct drill, some into cover which had been sprayed off with glyphosate about a month beforehand, and some into a standing cover which was sprayed post drilling.
Overall it has worked very well; we have some fantastic-looking crops following cover crops, better than others following overwintered fallow that was forced upon us by last autumns atrocious weather.
Establishment looks better where the cover had been destroyed. Crops sown into green cover got away well but have suffered since, so I plan next year to destroy cover crop in advance of sowing.
Blackgrass control is better in all spring-sown crops than those sown last autumn, he notes. I now have a Dale drill on order. We are using low-disturbance tines to start with and will sow at a much lower target speed of 6-7kph to minimise the chances of chitting blackgrass seed.
I dont think the soils are good enough yet for discs I think they would smear too much in damp conditions. The tines will create a little bit of tilth and some nitrogen mineralisation to help plants establish.
We are now focused on rebuilding fertility we need to try to get our soils back to where they were under a mixed farming system.
A nine-year rotation is planned. About 40% will remain as winter wheat, the farms most profitable crop. Winter barley and some winter oilseed rape will also feature, while a third of the area will consist of spring crops, including barley, beans and oats. All spring crops will be preceded by a cover crop, and the rotation will also feature at least one double spring break.
Mr Tuer is also introducing a partial CTF system based on the 8m drill. He believes this, cover crop roots and incorporating more straw will negate the need for annual soil-loosening cultivations.
I hope our new approach will can bring our soils back to where they were, as well as keeping on top of blackgrass and delivering viable spring crops. I hope we can do this without re-introducing grass, but Ive not ruled it out. Ill sell my min-till kit, but Im retaining the option of rotational ploughing for a year or two yet.
In addition to implementing the cover crop plan, the farm has been making use of Agrovistas Soil Health service.
The aim of the service is to provide growers with a summary of various key soil parameters to help highlight key practical steps to help improve their soil health, says Chis Martin.
The service uses electrical conductivity scanning to provide an accurate information on soil texture variation and topography across fields, providing an accurate base layer of information to make more informed decisions.
Adding farmer and agronomist knowledge helps provide a more accurate picture. All this can be used to draw up variable rate seed zones and can help target other inputs including slurry, FYM and biosolids.
As an option, satellite-derived biomass images and yield maps can be overlaid to indicate the effect of soil type on establishment and crop output. Data is gathered from several years to identify trends, which can be compared to soil type to establish where to look for limiting factors within a field.
Grower and agronomist then decide what action to take, says Mr Martin. Steve and I have yet to have those discussions due to the Covid-19 lockdown, but the reports will help us identify and implement the chemical, physical and biological solutions necessary to manage soils for the benefit of long-term farm profitability and soil stability.
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