Soil & Water 2018 conference: Getting cover crops to pay their way
With soil health and water quality likely to be at the heart of Government policy going forward, the Allerton Project, a pioneer in farm-based research in these areas, reviewed trial results at its recent conference, Soil and Water 2018.
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Marianne Curtis
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A three-year programme of research into cover crops, aiming to investigate how cover crops impacted soil biology, physics, chemistry, weeds and following crop performance, has been conducted at the Allerton Project as part of Defra’s Sustainable Intensification Research Platform (SIP).
Allerton Project soil scientist Dr Felicity Crotty said part of the project involved studying three cover crop mixes – oats + phacelia C + P; oats + rye + phacelia + tillage and oil radish (C + P + R); oats + phacelia + oil radish + crimson and berseem clover + vetch (C + P + R + L) and a bare stubble control treatment.
In autumn 2015 winter wheat was harvested on September 7 and cover crops sown on September 8. They were sprayed off on April 5, 2016, and spring oats sown on April 20.
There were significantly more surface dwelling earthworms in the two cover crop treatments which had radish in them (C + P + R = 133 worms/sq.m and C + P + R + L = 113 worms/sq.m) compared with the oats and phacelia only treatment (C + P = 13 worms/sq.m) and the bare stubble control (42 worms/sq.m), said Dr Crotty.
Fewer weeds
Weed biomass dry matter levels were measured in February 2016. The C + P + R (oats, phacelia and radish) mix had significantly fewer weeds (1.3g/sq.m) compared with all other treatments. C + P and C + P + R + L were intermediate (4.9g/sq.m and 10.7g/sq.m, respectively); while the bare stubble control had a significantly greater amount of weed material than all other treatments (30.6g/sq.m), said Dr Crotty.
The mix containing legumes gave the biggest yield boost in the following spring oat crop, which yielded just over four tonnes/hectare compared with just over 2.5t/ha for the control.
Further cover crop studies are continuing at Loddington as part of a partnership between King’s, Frontier and GWCT looking at the effect of different cultivation methods on a range of factors, including subsequent cereal crop yield. The methods include ploughing, no cover crop; ploughing plus cover crop; min till plus cover crop; low disturbance sub-soiler plus cover crop; and stubble plus spring cultivation.
King’s sales manager Richard Barnes said: “We envisage them continuing for at least three years.”
Loddington farm manager Phil Jarvis is keen for cover crops to deliver tangible economic benefits.
“We are getting the worms and soil structure but we need to make it more economic. There is no point in saving £50 on cultivation and losing £150 on yield.”
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Establishment methods
To try to gain a better understanding of why some establishment methods seem to work better than others, this year the research includes taking measurements of soil temperature and moisture in the top couple of inches of soil for each of the treatments from before cover crop destruction in early February up to grain fill.
Tackling run-off from tramlines
Reducing surface run-off from fields has been the subject of substantial research over the last decade at the Allerton Project, Loddington, Leicestershire, with the aim of developing advice to farmers on how to cut it. Promotion of catchment sensitive farming is also mentioned in the Government’s recently published 25-year Environment Plan.
Surface run-off can lead to washing of sediment and nutrients such as phosphorous and nitrogen into watercourses. This can reduce soil quality in the field and also have an adverse effect on water quality.
Management tool
While tramlines are an important management tool, they can increase risk of compaction, erosion, nutrient and sediment loss in run-off. Work done by ADAS showed 5-17% of surface run-off where tramlines were used compared with less than 0.6% where they were not.
ADAS research, reviewed by Prof Martyn Silgram and presented by Prof John Quinton, looked at the effect of different tramline management options over four UK sites, including Loddington, over four years.
Treatments included undrilled tramline wheelings; drilling the wheeling area; optimally-inflated ’very flexible’ (VF) tyres; tyres at road pressure (conventional control tyres – CT); a novel rotary harrow unit on a hydraulic toolbar attached to the back of the sprayer; a novel surface profiler roller-tine roller unit; CT plus rotary harrow; and optimally-inflated VF low ground pressure tyre plus rotary harrow.
Tyre pressure
There was no significant effect of drilling the tramline area on run-off or associated losses as the autumn spray operation still causes compaction and there was less topsoil compaction from VF tyres compared with CT tyres, according to the research.
VF tyres, rotary harrow and surface profiler units reduced run-off by up to 75%, 85% and 95%, respectively, compared to CT tyres and there was no effect of management treatment on crop yield.
In terms of cost effectiveness, VF tyres cost the least at £2/ha whereas the harrow (£12/ha) and profiler (£31/ha) require an incentive such as a Countryside Stewardship Scheme Capital Grant, according to the research.
Tramline management tips
- Consider using tramline management tools on high risk fields, i.e. moderate slopes near watercourses
- Re-orientate crop drilling and spraying so tramlines do not follow the steepest slope
- Increase tramline spacing, moving from, for example 18m to 24m
- Avoid over-inflating tyres
- Avoid using tramlines for spraying on loose, ’fluffy’ seedbeds or when soils are very moist
- Use an extra headland tramline disconnected from other tramlines at the lowest end of the field
- Consider re-orientating crop drilling and hence spraying direction so tramlines do not follow line of steepest slope
Source: Prof Martyn Silgram, RSK ADAS who had been due to present the paper on tramline run-off, but sadly died a few days before the Soil and Water 2018 conference.
Boosting organic matter
Suffolk-based arable organic farmer John Pawsey outlined soil health management strategies he employs at Shimpling Farms, Suffolk.
Mr Pawsey operates a 9m controlled traffic system to reduce compaction. He also uses intra-cropping.
“This keeps something growing all the time, smothering weeds or providing more organic matter; as one crop is senescing, the other is coming up.”
Mr Pawsey soil tests every four years using the loss on ignition (LOI) method for measuring organic matter.
“In 1999 our organic matter was 2.9 per cent and the latest 2016 test shows it is 5.5 per cent now.”
He spreads clean sugar beet pulp on fields to help boost organic matter from a British Sugar biodigester.
Where next for research?
A healthy debate took place at the Soil and Water 2018 conference about the value of academic and farmer-led research. Here are a few of the comments.
“There is a disconnect between academic research and what farmers are doing. The questions academics are asking are not the questions farmers want answering.”
Prof Jonathan Leake, University of Sheffield
“My farmers’ dairy discussion group has led me far further than anything from academia.”
Wil Armitage, Nuffield Scholar and dairy/mixed farmer
“There is so much form filling, ‘speak’ and ‘text’ – it is tortuous and needs to be easier to access.”
Richard Barnes, King’s on accessing BBSRC research funding
The Allerton Project
- The Allerton Project celebrated 25 years in 2017
- Investigates effects different farming methods have on the environment
- Evaluates and demonstrates farming practice designed to enhance wildlife and environmental quality
- Involved in many collaborative projects concerning soil health and water quality
- Appointed a soil scientist in 2015
318ha comprising 250ha arable, 29ha pasture and 18ha mature woodland in Loddington, Leicestershire, producing wheat, oats, oilseed rape and beans. Wheat and oats grown to Conservation Grade standards. Clay soils
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