Now in its ninth year, Agrovista’s Lamport AgX flagship trials site has evolved into the country’s leading workshop for sustainable agriculture.
4th August 2021
The Northamptonshire site, previously known as Project Lamport, is examining how rotations, cover cropping and regenerative agriculture principles can interact to improve soil health and yields while maintaining blackgrass levels at manageable levels.
It is a tough testing ground, situated on heavy, high calcium soils that are difficult to manage, with a background blackgrass population of 2000 plants/sq m. What works here should work for any grower, says Agrovista technical manager Mark Hemmant.
“When we took over in 2013, we ploughed down a massive amount of herbicide-resistant blackgrass, and ploughed up a smaller amount of less resistant seed.
“The aim from then on was to try to minimise seed return and leave what we had ploughed down as long as possible, to let nature deal with it.”
Work on the large-scale, tramline-width plots concentrated on achieving the best cultural control possible using various rotations, mostly based around cover cropping followed by spring cereals. “It was obvious we couldn’t rely on chemistry alone,” says Mark.
“It also became increasingly clear that the techniques we were using had valuable benefits on soil health, something that has become much more topical over the past few years and is now a potential revenue stream. Soil health has therefore become a key focus at the site.
“We are also adopting some regenerative agriculture principles and incorporating them into conventional agriculture, which may result in a more sustainable system.
“But, we know from our work here that if you take your eye off black-grass, you can soon be in a muddle. Lamport AgX is unique – we can look at all these things together, while asking if we can we keep black-grass under control.
“What started as a way of helping farmers to keep growing profitable crops with a high background level of blackgrass has turned into something a lot more encompassing, interconnected and exciting.”
Blackgrass control – the Lamport system
Over the years, Agrovista has refined an autumn cover crop/spring cereal rotation to keep blackgrass under control.
A cover crop, based on black oats, is established in early autumn after a light cultivation to maximise blackgrass establishment, before bulking up to condition and drain heavy soils over winter to enable spring drilling.
The cover crop and ‘trapped’ black-grass are then sprayed off ahead of the spring cereal, which is established with a direct drill to minimise soil disturbance and blackgrass emergence.
“The aim is to get lots of blackgrass to germinate in the autumn, and none in the spring,” says Mark. “Everything else bolts on around this.”
However, he acknowledges that most farmers will want to return to winter wheat as soon as possible, given the potential returns.
Recent work has shown that this is feasible, but perhaps only one year in three on site such as Lamport where the resistant blackgrass seed burden remains very high, even after eight years of cultural and chemical controls.
Legume fallow – AB15
One option to help farmers return to winter wheat uses a legume fallow to control blackgrass while improving soil heath. AB15, a two-year legume fallow, is available under Countryside Stewardship mid-tier.
Niall Atkinson, consultant and trials coordinator at Lamport AgX, says the option looks quite inviting.
“The scheme pays £522/ha, while seed costs £75-90/ha and you’ll have to mow a few times. But you have to sow the cover before the end of August, so you are planting into a potentially high blackgrass situation.”
Final establishment on the heavy Lamport soil was poor, resulting in a carpet of blackgrass that outcompeted the clover. In addition, the shallow rooting system of the blackgrass, coupled with aggregation of soil fines after heavy rain, created a pan at around 5cm depth, severely reducing water infiltration and creating anaerobic conditions.
The plot has been since been mown four times, but this has resulted in successively shorter blackgrass seed heads and a potentially high seed return.
“This option has done nothing for blackgrass control and nothing for soil health, and environmentally all this mowing has been a bit of a disaster,” says Niall.
Mark adds: “If you are considering this option, think about what your starting point is. The first four years at Lamport were spring cropping, followed by two years of winter cropping, but our blackgrass levels were too high to successfully establish AB15.”
Legume fallow - alternative option
An alternative to AB15 at Lamport appears to be much more beneficial for soil health and has resulted in a following crop of winter wheat.
A black oat and phacelia cover crop was established in August 2018 to trap blackgrass and condition the soil. It was desiccated the following January and again just before the AB15 mix of various legumes was established in the spring.
“The legume mix grew away very well and we didn’t need to carry out successive mowing top control blackgrass. We sprayed off the AB15 mix in August 2020 and in October established winter wheat with a direct drill to minimise blackgrass germination.”
“You can see the odd blackgrass plant but control is very acceptable – the wheat looks like a 10-12t/ha crop,” says Niall. “We’ve made this work by utilising everything we’ve learned at Lamport over the past few years about controlling blackgrass.”
Tempting though it may be, the winter wheat will be followed by a return to the cover crop/spring crop sequence for at least two years.
“You can understand why people might go for a second wheat, especially at current wheat prices,” says Mark. “But blackgrass explodes. Even after seven years of very low seed return at this site, we still haven’t depleted the weed seed bank sufficiently to be able to rely on chemistry.
“Blackgrass is a numbers game and we started off with a huge population. In the past, second wheats here have yielded 5-6t/ha rather than 10-12t/ha, after spending a fortune on chemistry. It doesn’t pay the bills.
“Returning to the cover crop/spring crop sequence will pay better in the long run, doing a fantastic job on both soil health and blackgrass.”
The modified AB15 is not allowed under mid-tier rules, but could be under the Sustainable Farming Incentive two-year legume fallow, which can be planted in the spring.
But further clarification will be needed, as it appears the legume mix has to be left in the ground for two calendar years, which could mean having to follow with a spring crop rather than returning to winter wheat.
Winter wheat – Lamport system
A further method tested under extreme conditions looks more promising for growers who want to return to winter wheat without sacrificing one or two years of cash cropping.
It is being carried out on a plot where in 2019, a third winter wheat crop failed after being overwhelmed by blackgrass, despite a £150/ha herbicide spend.
The plot was divided, with the front half earmarked for ploughing and the rear half a cover crop/spring crop sequence.
“We carried out two to three shallow stale seedbeds in autumn 2019 on the front half, with the intention of ploughing in mid October,” says Niall. “We achieved a great chit of blackgrass, but got to mid-October and the heavens opened. We couldn’t get near it with a tractor, so it never was ploughed.”
Blackgrass thrived in the wet spongy conditions, and nothing could be done until spring 2020 by which time ploughing was out of the question. Thoughts of a cash crop were abandoned and a summer cover crop was established.
In the other half of the plot, the cover crop was drilled on 5 September 2019 after light cultivation. “The value of shallow soil movement in the autumn really showed this year in terms of blackgrass control and benefiting the following cash crop,” says Mark.
The cover grew away well, trapping blackgrass and conditioning and draining the soil. The cover was desiccated early January and spring oats were direct-drilled on 27 March 2020 and went on to yield just under 8t/ha.
“We then direct-drilled winter wheat in mid-October when conditions were on the limit,” says Niall. “Despite that, two years after what had been a disaster, the plot is carrying a very promising first wheat with low blackgrass levels.
“Conventional wisdom says we should have pressed the reset button and ploughed, but we have shown an alternative that lets nature deal with what lies underneath.
“The wheat looks almost as good as that following our modified AB15, perhaps heading for 9-10t/ha, but we’ve also had an 8t crop of spring oats in the meantime and have ended up with very little blackgrass.”
The plot will return to an autumn cover crop/spring crop sequence. “We know the weed seedbank is awful here – there is no way we have flushed all the blackgrass, so we have to stick to the principle of rotations,” says Mark.
Early cover crop destruction vital
Spraying off an autumn-sown cover crop around Christmas is the key to successful spring cash crop establishment.
“Early destruction has consistently shown 0.5-0.7t/ha yield advantage over leaving the fields fallow during the autumn and winter,” says Mark. “The cover crop still has time to deliver all the soil health benefits and the spring crop tends to grow away more vigorously.”
Chris Martin, head of soil health at Agrovista, says: “Decomposition starts when earthworms start taking trash down. If you drill the cash crop in to a green cover, the benefits of this will not be seen for several weeks.
“Early decomposition will increase soil microbiology at the time of drilling. This might be a bit counterintuitive to what we might think, but work shows this is the case – microbes benefit from the cover crop decomposition process.”
Breaking down high carbon:nitrogen ratio material like plant debris also comes at a nitrogen cost. “If this process has happened by the time the cash crop is drilled, the resulting material will be releasing nutrients, including nitrogen, which will be available to the cash crop.”
Early destruction also reduces the amount of organic acids in the soil at drilling. These compounds, products of plant material breakdown, can potentially inhibit seedling growth. “Recycling and removing them from the system will benefit the following crop,” says Chris.
Regenerative principles on test
A further study at Lamport is assessing the prospects of reducing reliance on conventional agrochemicals. A plot of spring wheat was sown in late March, along with sweet allyssum to encourage beneficials and berseem clover to condition soil and fix nitrogen.
“We’ve basically taken away conventional chemical inputs,” says Mark. We’ve used no fungicide seed treatments, no herbicides and minimal foliar fungicide use.”
The plot received 20kg/ha of controlled release foliar N, replacing 100kg/ha of conventional N to reduce the amount of free nitrogen in the soil and to help cut the carbon footprint. The reduced early nutrition appeared to cut blackgrass numbers.
A comprehensive biostimulants programme was also adopted, including NUELLO® iN seed treatment to fix N and, with seedbed-applied Phosphorus Liberator, to release soil phosphate. Amino acid products Klorofill and T6P were applied at conventional fungicide timings, along with L-CBF Boost, a food source for soil microbes and fungi.
“This approach seems to have worked well,” says Mark. “There was very little disease in the plot – a little more Septoria than some of the others, and a small amount of late rust, which we controlled with a low rate of tebuconazole.
“It’s a really interesting concept, and the interaction between the various elements is really exciting. Often trials only look at one thing in isolation and suggest it doesn’t work – but it might in combination with something else.
“If we can adopt areas of regenerative farming and fit them into a conventional system to make it more sustainable, that has to be a good thing.”
Direct-drilled spring beans
Spring beans are being trialled at Lamport AgX to introduce a true cereal break.
Given the lessons learned over the past eight years, establishment was the key issue.
“I was always told that good autumn ploughing was crucial for spring beans,” says Mark. “But last thing we want to do here is plough. Instead, we carried out a low-disturbance shallow soil loosening when we established the cover crop to aerate the soil without mixing blackgrass seed through the soil profile.
“We direct drilled the beans in spring. We had twice as much biomass at the beginning of June than another plot where we didn’t move any soil, and there is very little blackgrass.
“This could be a valuable way of introducing beans in to the system – the crop is low carbon, provides a nitrogen benefit to the following crop and is good for soil heath, as well as being a good introduction for first wheat.”
De-risking oilseed rape
Work examining the potential of broadcasting cover crops into the previous standing continues this coming season, but with a twist.
“We think the process will work best with small-seeded species, so we’ve been trying phacelia, linseed, buckwheat and berseem clover to provide a range of rooting profiles,” says Mark.
“This season we are adding oilseed rape at 5-6kg/ha and fenugreek, which apparently can act as a flea beetle deterrent.
“If the oilseed rape establishes well, then we will spray off the cover crop. If not, we’ll be left with a cover crop with a bit of rape in it and we can revert to spring cash cropping.
“This has really captured the imagination of visitors. This could be an excellent way and low-cost way of de-risking the crop when using farm-saved seed.”
Soil heath – key tests
Soil health has become a buzzword in arable circles, but how it should be effectively measured remains a keen discussion point.
Chris Martin, head of soil health at Agrovista, says: “Everyone is trying to find the best way to measure soil health. The truth is, there is no black and white method – at Agrovista we’ve tried to create something that is useful and ticks all the boxes for ELMS and Farming Rules for Water and provides measurements growers can use.
“Agrovista’s Gold Soil Heath Report analyses the most significant chemical, biological and physical aspects, producing key indicators to help farmers drive things forward, painting a picture of how soil will behave, and ¬what sort of machinery, fertiliser and timings we need before we even put a spade in the ground.
“This is really transforming the way we look at soils, particularly with drive to min-till and direct drilling.”
Chemical aspects
The soils at Lamport are typical of many heavy, high PH soils with elevated levels of calcium and magnesium that are tricky to farm.
The very high pH, around 7.7, is key when it comes to nutritional decisions. Using a standard fertiliser regime won’t produce the full benefits as traditional phosphate fertilisers will get locked up very quickly, within a matter of weeks.
“Farmers have wasted millions of pounds over the years on these sorts of soils,” says Chris. “Phosphorus has ended up in a huge immobile pool and soils like these are full of insoluble phosphate, but we keep adding more and more. Rather than adding it we need to release it.”
Trials are examining technologies to do just that. Phosphorus Liberator, a carboxylic acid salt that breaks down calcium phosphate, is showing particular promise – replicated results show a 0.5t/ha yield benefit on spring wheat when using the product.
“This shows we are better off using what we have in the soil. It is cheaper and environmentally beneficial – P is a finite resource and can also find its way into watercourses.”
The gold report assesses all key nutrient statuses in similar detail, so that growers will know what to apply and when to match nutrition to need. This is backed up with leaf tissue and sap testing as required, and reviewed with a grain test says Chris.
Physical aspects
The physical properties of a soil indicates how it is going to behave. At Lamport, the high Ca/Mg ratio of around 25:1 shows the soil will tend to flocculate.
However, the soil also has a very high silt content, above 50%, says Chris. “When it flocculates, it opens up, but the fines then run together when it rains. If there is no crop in the ground over winter, the surface gets incredibly hard and tight and potentially anaerobic.
“It’s like a vertical river – all the fines run together until they hit a dam and build up. Where there is blackgrass this occurs at around 5cm depth where most of the root mass occurs – they don’t go much deeper. Compaction can be significant – a penetrometer reading of 200lbs/sq in is not unusual.
“At some point we need to get a tine in. We could use a tine drill to drill the cover crop to get biology to breathe and stir the soil, then use a disc drill for the cash crop to minimise soil movement and blackgrass germination. It might be worth considering two drills, and selling some cultivation machinery.”
Some people believe soil should not be moved at all, to protect soil biology and to avoid CO2 loss. But with tight soils, a little movement to introduce air and help soil biology flourish will pay dividends.
“Light cultivations will mineralise some organic matter, but this short-term loss of carbon will be offset by an increase in microbes and the resulting increase in high quality OM,” says Chris.
A deeper pan due to historical cultivation strategies often occurs at 10-15cm that biology won’t penetrate, but at this depth it is usually too wet usually for metal to work alone.
“A deep subsoiling will denature the soil even more. You need a combination of roots and just enough metal, such as a low-disturbance leg, as well as earthworms, to do the job,” says Chris.
Biological aspects
At Lamport, organic matter (OM) levels are low. The actual figure is 3.9%, but every field has a different capability. “Dividing clay content by organic carbon shows us there is huge potential to build OM on this soil – we need to get to 5 to 6%,” says Chris.
How to do that most effectively depends on several factors. “The C:N ratio is balanced here, which demonstrates that carbon is working after eight years of work on this site. Most farms have a lower C:N ratio due to lots of cultivations and bacterial-dominated soils – these are turning OM over very quickly but not building levels.
“We need to aim for a soil C:N ratio of 10 to 12 – we are then obtaining nutrient value from OM and building levels.
“Depending on a farm’s ratio we can determine how to best build OM. Do we need low carbon materials like slurries and digestate, or are we better bringing in more stable things like chopped straw, compost, or paper waste?
“Most farmers use the same inputs year on year, putting things further out of balance. It is not always a question of using the simplest most straightforward source you can. Here, though, standard FYM would be fantastic.”
Soil health measurement should really look at trends rather than precise figures, says Chris. “Biology is living medium. We are never going to get meaningful repeatable indicators, something we as an industry have been very guilty of trying to find.
“What can we use are trends. Soil respiration is a good example – it is a measure of CO2 production, a crude indication of how much biology is breathing in the soil.
“We call this the canary in the mine – it is represented as a figure, but in an arable system if it is lower than 100mg CO2/kg of soil that would tend to suggest something is wrong.
“It’s a really good indicator you need to go out with a spade to see what’s happening. More detailed tests mean nothing from practical point of view - this one is quite useful, and growers will have to adopt it as part of ELMS anyway.
However, is a high reading always necessarily good, or might it indicate too much carbon is being lost from the system? An active carbon test, newly imported from the USA, can reveal the answer.
“This measures the freshest forms of carbon, such as root exudates, providing a good correlation between active carbon and long-term OM build up,” says Chris.
“We run this alongside soil respiration – if both are high, that means there is lots of biology cycling carbon. If one or both are low, there is either not enough biology in the soil, or what is there is not capturing carbon, so you need to make managerial decision to correct it, such as a cover crop to ensure carbon is not being lost.
“Everywhere there are roots, there is biology, and where there’s biology, there are healthy soils.”
* The Gold report costs a few pence an acre per year more than the standard test now required to comply with the Farming rules for water. “The phosphorous alone we have saved at Lamport would pay for that 100 times over,” says Chris.