Project Lamport review - 2020

Project Lamport - bridging the gap between science and on-farm practice

Introducing cover crops and extending and diversifying the rotation is delivering rapid and significant soil health benefits on the heavy silty clays at Project Lamport, Agrovista’s flagship trials in Northamptonshire.

The site was set up in 2013 to investigate cultural solutions to help control severe blackgrass infestations while maintaining a profitable combinable crop rotation.

The project has been incredibly successful in that aim. Introducing a wider diversity of cropping, such as growing a spring crop after a black oats-based cover crop, was the key driver in depleting the blackgrass population at the site.

It also became evident that this sequence was delivering some very significant improvements in soil structure, drainage and biology.

Chris Martin, Agrovista’s head of soil health, says: “Now we are getting on top of blackgrass, we’re looking in more detail at how some of the techniques we’ve been using are helping to improve soil health.

“With cover crops, we are trying to maximise the use of our most valuable resource, sunlight, converting it into roots that naturally restructure the ground and feed the soil biology. We are now starting to measure this, with some very exciting results.

“Project Lamport has been really successful project at controlling blackgrass. Now, from a soil heath point of view, it is proving to be a really useful bridge between the science and theory and what is practically achievable on farm.”

Visible improvements ‘quicker than you’d think’

Using the right cover crops can visibly improve soil health and bring about real benefits in a few months, according to research by PhD candidate David Purdy.

David, who is also John Deere’s East Anglia territory manager, is examining the effects of cover crops on soil heath and crop yields.

Treatments include undisturbed soil, low-disturbance subsoiling at 12 and 20cm, presence and absence of cover crops (black oats/phacelia) and two soil compaction treatments (at 9 and 18 psi).

Over the past two years, growing a black oat cover crop through the autumn and winter has resulted in very significant improvements to topsoil structure by the following spring, compared with fallow (VASS TEST PICTURES).

“The soil after the cover crop was nicely aggregated, with a more friable structure. This created an excellent environment for rooting and soil biology to benefit the following spring crop,” says David. “The soil without the cover was blocky and angular, difficult to break and had very little biological activity, indicated by low worm counts.”

A similar result was obtained on ground pre-compacted using a tractor with tyres inflated to 9psi and subject to low-disturbance loosening at 20cm with a Meir Soil Conditioner when the cover crop was established.

“This reinforces the valuable role that cover crops can play in enhancing soil health and clearly illustrates that the process happens a lot quicker than you’d think,” says David.

The beneficial effect of cover crops on soil biology was demonstrated by a dramatic increase in worm numbers, across the site.

“Wherever we put a cover crop plant in the soil, we got a significant response in worm count and overall achieved a very significant increase in numbers. Worms are a key indicator and enhancer of soil biology, so the result demonstrates how much this has increased in a very short time.”

Cover crops dominated by black oats appear to be particularly good at increasing earthworm numbers, he adds. “It was quite dramatic – numbers declined where there were no roots, even a foot away.”

The rapid improvements in soil structure and biology fed through to yield , says David. “The mean yield increase for spring wheat following a cover crop was 0.5t/ha compared with the overwintered fallow.”

Thriving plants

There was a very significant relationship between the amount of cover crop, expressed as normalised difference vegetation index (NDVI), and spring wheat yield . “This shows that the biomass of the cover crop creates an environment in which the spring wheat plants can thrive.”

This was reinforced by the very strong correlation between higher spring wheat ground cover levels, reduced soil shear forces and lower penetrometer resistance readings.

There was an especially strong relationship between penetrometer readings at 7.5-10cm, less so at depth. “This is pivotal,” says David. “It suggests if you can sort out soils down to 10cm that will suffice for spring cropping – even if you have compaction at 20cm, it doesn’t matter. All you need to do is get a good cover crop going and the roots will do the rest.”

Spring wheat ground cover was also closely related to the amount of active carbon in the soil. Active carbon represents carbon energy sources on which micro-organisms can feed, so is another good indicator of soil biology.

“This was a very powerful result,” says David. “As the active carbon increased, we saw better spring wheat growth.”

Assessing the need for cultivations

Independent cultivations expert Philip Wright is investigating how much metal is required when establishing cover crops to optimise natural soil restructuring on Lamport’s silty clays.

“The key is to create the optimum environment for the spring crop using natural wetting and drying cycles, rather than intensive cultivations,” says Philip. “The ultimate aim is to improve the health of the soil to the point that a cover crop alone will suffice.

“The combined effects of roots and metal have been very real on this heavy-land site, especially in the early years of cover cropping. But we also believe we can reduce the amount of metal we are using. We need to get these cover crops in early so the roots can go to work, and use just enough metal to help them do their job.”

The work is being carried out on a heavily compacted area that had been used for unloading equipment with no history of cover cropping, providing a tough test, says Philip.

The trials consist of direct-drilled spring wheat after overwintered fallow, or after black oat and phacelia cover crops broadcast at 15kg/ha on 11 September, with and without soil loosening using a HE-VA subsoiler. Low-disturbance points were used on half the loosened plots and standard (high-disturbance) points on the rest.

The cover crops were sprayed off in early February and the spring wheat was sown on 26 March.

Low-disturbance subsoiling at 20cm and cover cropping produced the best result of all. “This soil is much easier to break apart and the pores and channels are obvious.

Stretch and lift

“The operation lifted and stretched the soil sufficiently for the cover crop to bang down its roots and hold the soil apart, without causing excessive movement. The spring wheat has exploited this and grown to depth. There are more tillers and more heads, and we think this will feed through to yield.

“This now begs the question: can we go shallower?” says Philip. “David’s work suggests we can. The trick is to hit the point where compaction is alleviated just enough for the roots to do the rest. Lifting out 4-5cm can halve the draft, conceivably saving around 10 litres/ha of fuel.”

How much cultivation will be needed in successive cover crops is open to question, says Philip. “If you minimise damage at harvest, avoid compacting non-tramline areas as much as possible and you don’t get too much bad weather afterwards, the default position should be no cultivation, unless the spade tells you otherwise.”

“Inevitably there will be times when we cause problems. But if we have more healthy roots in the soil we know using a low-disturbance point will be enough to provide the fissures and pathways the roots need to do their job of natural restructuring. “

Compaction indicator

However, identifying areas that do need treating can be very time consuming. One useful solution could be to plant a cover crop straight after harvest and use it to indicate where subsequent soil loosening is required.

“Rather than delay you get the cover crop in as soon as possible so it can start doing its job,” says Philip. “Once roots hit significant compaction the crop will start to struggle, clearly showing where remedial action is needed.”

Point selection is critical to avoid excessive crop damage. “Standard low-disturbance wings at 10-12cm deep really knocked the crop, especially in dry conditions. Shallower-angled wings provided sufficient disturbance but less crop damage.”

Root measurements on treated and untreated areas showed how effective the treatment had been. “The difference was amazing,” says Philip. “The roots were released to exploit the more open soil, probably helped by a bit of mineralisation and aeration as well.”

Outstanding resilience in a wet season

The beneficial effect of cover crops in practice stood out during the exceptionally wet autumn and winter at Project Lamport.

Plots cropped with the overwintered cover crop/spring wheat sequence allowed water to infiltrate much more readily than those fallowed ahead of the spring wheat.

“We rarely saw any surface water on the cover-cropped plots even after the heaviest of rain,” says Agrovista’s farm systems research and development adviser Niall Atkinson.

“There was very little puddling, and what there was disappeared quickly, whereas the fallowed plot suffered badly, despite having been subsoiled in the autumn. The soil ran together and fines were washed into the channels, sealing the surface.

“This is a problem we see year after year on high silt soils. You end up having to cultivate it again in front of the spring crop, which destroys any structure that might remain.”

The benefit of the subsoiling on cover crop growth was evident in some plots. “Soils were wet and cold and cover crops on their own didn’t establish as well as usual,” says Niall.

“They still did a good job, but where we had identified a need and used the subsoiler as well, we got a better result with the cover crop and a slight improvement in spring wheat establishment.”

Exceptional blackgrass control

Blackgrass control in the spring wheat remains outstanding this summer on the plots that have been cover cropped . “This year we counted fewer than one head/sq m,” says technical manager Mark Hemmant.

System 3: Combi-drilled cover crop / DD S.Wheat

“That’s in line with previous findings; head counts have been kept in single figures/sq m since the standard cover crop/spring wheat sequence was introduced 2013, despite the site having a background population of 2000 plants/sq m.

“In the spring wheat after subsoiled fallow we counted over 100 heads – we ended up moving more soil in the spring as there were no remnants of cover crop roots to hold the soil together. This system is not controlling blackgrass sufficiently and is doing nothing for soil health.”

No-plough reset gets blackgrass control back on track

Reverting to winter wheat too soon can result in an explosion of blackgrass and potential crop write-off, says Mark.

“When this happens, the standard advice is to press the reset button and plough. Last summer we planned to put this to the test on a plot that had grown a disastrous winter wheat crop with over 800 blackgrass heads/sq m.”

The plan was to split the plot in half, with one side subject to traditional stale seedbeds followed by ploughing and spring cropping, with the other following the Lamport system of establishing a cover crop to trap the blackgrass followed by direct-drilled spring crop.

Unfortunately, due to the wet conditions plans to plough were abandoned. As a consequence, no spring cropping could be carried out on that half of the plot.

The Lamport system area was straw-raked and shallow-disced on 5 September, then combi-drilled with 15kg/ha of Agrovista’s Sprinter Pro black oat and phacelia cover crop mix on the same day, then rolled soon afterwards.

Black oat and phacelia

The ensuing cover, along with emerged blackgrass, was sprayed off with glyphosate + Companion Gold on 5 February and again on 25 March. Spring oats were direct drilled with a no-till Weaving GD drill at 350 seeds/sq m on 27 March. The only residual herbicide applied was 100g/ha of DFF (as 0.2 litres/ha of Hurricane) plus Remix on 1 April.

“We established an excellent crop of spring oats and achieved fantastic blackgrass control,” says Mark. “We trapped young plants successfully in the cover crop and minimised soil disturbance when the oats were drilled.

The no-plough reset resulted in fantastic blackgrass control and an excellent crop of spring oats

“We took a really bad situation and turned it around, which gives us confidence that this could be a viable option when resetting the system, without risking pulling up more blackgrass seed than you are burying. And, from a soil health point of view, you won’t be undoing all the good you have done.”

Cover crop establishment – reducing soil damage

Ultra-shallow discs have superseded the power harrow as the tool of choice for cover crop seedbeds at Project Lamport.

“When establishing the cover crop the aim was to try to make the blackgrass grow within it so we could trap it and destroy it with glyphosate ahead of the spring cereal,” says Niall.

“At the start of the project we used a power harrow to achieve the necessary soil movement. It did a really good job of establishing the cover crop and setting off the blackgrass, so we had a really good kill.

“However, it has become increasingly evident how much damage power harrowing was doing to soil structure and soil biology. So we’re now trying to move less soil.”

A Vaderstad Carrier fitted with CrossCutter discs designed to work at just 2-3cm is now being used. “This still provides a very good blackgrass chit, but without the detrimental effect of the deeper rotary cultivation,” says Niall.

Straw raking has proved very useful where a light cultivation is not required, spreading crop residues and giving a good chit of volunteers and grass weeds, offering a step up in soil health terms through less soil disturbance, he adds.

However, the cover crop/spring wheat sequence has been so successful that stimulating a pre-cover blackgrass chit is not always required.

“We are examining the feasibility of blowing the cover crop into the previous crop. If successful, this would enable more timely establishment of the cover while removing a cultivation, further benefiting soil health.”