COVER CROPS TECHNICAL GUIDE - Agrii
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COVER CROPS TECHNICAL GUIDE
WHAT COVER CROPS CAN DO
Cover crops used correctly as part of your soil management strategy can deliver the following benefits:
✚ Capture and recycle nutrients left over ✚ Increase the quantity of the biota
from the previous crop, rather than being (bacteria, earthworms, fungi, insects) ✚ In the longer term, cover crops used
leached away. in the soil over time by having a as an integral part of the farming
✚ Fix nutrients from the atmosphere in growing crop and increased organic strategy will improve farm incomes
association with soil bacteria. matter available for more of the year and sustainability by increasing
to feed them consistently. The increase soil fertility and productivity whilst
✚ Improve soil structure through root in soil biota will then speed up the reducing input costs.
penetration at different depths – subject breakdown of organic matter, bring the
to the species used. Channels created by ✚ In our own trials work we have
carbon:nitrogen ratio into balance and already seen some of these
the roots open up the soil allowing free make nutrients readily available to the
movement of air and water through the benefits from the use of cover crops
cash crop. compared to fallowing land between
soil profile, even breaking up compacted
layers at depth. ✚ Growing the appropriate species and cash crops.
varieties of cover and companion crops ✚ The key element in improving soil
✚ Protect the soil from erosion by water for your farm rotation can help reduce
and wind, by holding soil in place with health and productivity in the long
pest problems, particularly soil nematodes term, is to increase its organic matter
root and foliage growth. and cabbage stem flea beetle. content and maintain living roots
✚ Help to suppress weed growth either ✚ Potential to save on cultivation costs by in the soil for as much of the year
by direct competition and/or by direct drilling following a cover crop that as possible. This can be done by
allelopathic effect. has improved or maintained soil structure. selecting the correct cover crops for
✚ Create a large biomass of fresh organic ✚ Encourage farmland wildlife and your farming operation.
matter which, when returned to the soil, beneficial insects by creating cover and
will release nutrients over time to the a food source over an extended period.
following crops through the action of the
soil biota. This helps to build organic ✚ Improve overall soil health, which is the
matter levels and improve soil structure, foundation for helping to promote good
particularly in low soil disturbance crop health, enhancing crop yields and
establishment systems. farm sustainability.
2 Cover Crops Technical Guide
WHY SOIL HEALTH IS IMPORTANT
Soil is fundamental for crop production, supporting delivery of 95% of
the UK’s food, and storing around 80 years’ worth of GHG emissions The ‘One Health’ concept
in the form of carbon.# Soil health can be defined as the continued Shows the relationship between ecosystems – soils, plants, animals
capacity of a soil to function as a vital living ecosystem that sustains and human health as being closely intertwined. (Adapted from:
plants, animals and humans. Healthy soils grow healthy crops that The soil- human health nexus. Edited by Rattan Lal, 2021.)
are better able to withstand disease and compete against grassweeds.
Agrii was one of founding partners Soil Plant Animal Human Environment Planet
of the Harper Adams Soil and Water Health Health Health Health Health Health
Management Centre.
Soil is an ecosystem that can be managed:
✚ A healthy soil provides a habitat for ✚ The carbon contained within soil ✚ A well structured soil anchors ✚ Soil isn’t an inert growing
soil microbes to flourish and diversify organic matter represents one crops and plants – allowing root medium. Rather, a healthy soil
– providing the nutrients that crops of the largest carbon stocks on systems to extend downward is home for billions of organisms,
need to grow and prosper. Earth and plays a major role in through the soil and in turn including bacteria, fungi, insect
✚ Soils store two thirds of the fresh mitigating climate change. In the stabilise plants so that they larvae and earthworms that are
water on the planet* and this UK our soils hold an estimated can grow efficiently. the foundation of an intricate
function is determined by the level 9.8 billion tonnes of carbon.** ✚ A well structured soil allows below-ground ecosystem.
of organic matter in the soil. The When soil is eroded, the carbon less erosion by wind or rain and ✚ Most of these organisms – big
loss of soil biodiversity reduces stored in soils is lost in the form of reduces the likelihood of flooding and small – are an essential part
its water infiltration capacity, as greenhouse gases. Globally it is due to improved porosity. of enhancing the nutrients that
well as its capacity to store water, estimated that 26% of the carbon stimulate plant growth.
stored in the top one metre of soil ✚ The minerals and microbes in
lowering food production and soils help to filter, buffer, degrade
worsening the impact of drought. has been lost since pre-historic #
Environment Agency 2019
times (FAO 2015). and detoxify potential pollutants * IUCN - www.iucn.org/resources/issues-
– including industrial by-products briefs/conserving-healthy-soils
INSIGHT REPORT:1
and atmospheric pollution. **Soil Association figures
IMPROVING
SOIL RESILIENCE
More information on the potential benefits of cover crops to soil health and organic matter
levels can be found in Green Horizons Insight Report 1: Improving Soil Resilience.
GREEN HORIZ NS
www.agrii.co.uk
Please go to www.agrii.co.uk/greenhorizons to view, or ask your agronomist for a copy.
Cover Crops Technical Guide 3
COVER CROP VARIETIES IN DETAIL
BRACO – WHITE MUSTARD STALA – PHACELIA
USE NCAP EB NCAP EB
Late summer, mid September latest. Late summer drilled crops need to go in before the end of
DRILLING Full seed rate drilled at 12kg/ha. Typical TGW 8g. August. Full seed rate drilled at 10kg/ha. Typical TGW 2g.
If late summer sown, a strong frost should destroy the crop, If late summer sown, the frost will destroy the crop
HOW TO
although root and stems will remain. In the south it may leaving very little residue. In a mild autumn it may
DESTROY need spraying off or rolling before it sets seed. need spraying to stop seed set.
✚ C:N ratio 30. ✚ C:N ratio 20.
✚ Reliable, very fast establishment. ✚ Reliable, fast establishment.
OTHER ✚ Good at extracting moisture and nutrients from ✚ Very fibrous root system down to 8cm creating a very
INFORMATION the upper soil profile. good soil structure in drilling zone.
✚ Beet cyst nematode reducing variety. ✚ Good surface nutrient capture and weed suppression
✚ Lower seed cost. when growing.
4 Cover Crops Technical Guide
Soil Nutrient Nutrient Frost Grazing/ Environmental
KEY:
Nematode Weed N
Structure Reduction Control
NCAP
Capture PROD Production Susceptible Silage EB Benefits
CADENCE/LUXURIAL – BLACK OATS FORAGE RYE
USE NCAP NCAP
Best sown late summer, before end of August. Best sown from mid August until early October.
DRILLING Full seed rate drilled at 30kg/ha. Typical TGW 20g. Full seed rate drilled at 160kg/ha. Typical TGW 38g.
HOW TO Black oats are frost sensitive and can die back naturally
Spray off in the spring or graze or silage.
DESTROY during prolonged cold periods.
✚ C:N ratio 25.
✚ Good establishment. ✚ C:N ratio 35.
OTHER ✚ Large fibrous root system creates good soil structure. ✚ Reliable, quick ground cover.
INFORMATION ✚ Resistant to diseases, take all and good tolerance ✚ Extensive root system, good scavenger of nutrients,
to BYDV. will continue to grow even in cold conditions.
✚ Reduction of root knot and root lesion nematodes.
Cover Crops Technical Guide 5
COVER CROP VARIETIES IN DETAIL
BINGO/TITANE – PURPLE SPRING VETCH TABOR – BERSEEM CLOVER
N N
USE NCAP PROD EB NCAP PROD
Drill before the end of August. Drill before the end of August at 10-15kg/ha.
DRILLING Full seed rate 30kg/ha. Typical TGW 39g. Typical TGW 3g.
HOW TO
Late summer sown, a strong frost should destroy the crop. Late summer sown, a strong frost should destroy the crop.
DESTROY
✚ C:N ratio 14.
✚ C:N ratio 12.
✚ Tabor is a single cut variety that will not regrow
OTHER ✚ Purple vetch are the fastest growing of the vetch species,
if topped.
INFORMATION which enables them to catch and fix the maximum
✚ Very quick growing with a long tap root.
amount of nitrogen in the limited time available.
✚ Useful as a companion crop for OSR.
6 Cover Crops Technical Guide
Soil Nutrient Nutrient Frost Grazing/ Environmental
KEY:
Nematode Weed N
Structure Reduction Control
NCAP
Capture PROD Production Susceptible Silage EB Benefits
CEGALO – CRIMSON CLOVER ASIAN/DAIKON RADISH
N
USE NCAP PROD EB NCAP
Full drill rate 15kg/ha before the end of August. Best sown before the end of August.
DRILLING Typical TGW 5g. Full seed rate 12kg/ha. Typical TGW 20g.
HOW TO
Spray off, if not killed by frost. Will be destroyed by a hard frost.
DESTROY
✚ C:N ratio 16. ✚ C:N ratio 35.
OTHER ✚ Faster establishment and good biomass. ✚ Very large, strong tap root, good for soil
INFORMATION ✚ Strong tap root and lateral roots. structure improvement.
✚ Large root scavenges and holds more nutrients.
Cover Crops Technical Guide 7
COVER CROP VARIETIES IN DETAIL
OILSEED RADISH NEMATODE REDUCING VARIETIES
Group 1: Reduction of Beet Cyst Nematodes by over 90%
KWS REBELLION
✚ Very high levels of BCN reduction.
✚ Good early vigour.
✚ Medium biomass.
✚ Extensive strong root system.
✚ Very late maturity.
✚ Frost hardy to -5ºC.
Group 2: Reduction of Beet Cyst Nematode of 70-90%
USE NCAP
COBRA
✚ Multi resistance to beet cyst and root knot nematode.
Sow from late July to mid September. Full seed rate (Meloidogyne chitwoodi).
DRILLING 12-20kg/ha depending on use. Typical TGW 11g. ✚ Very vigorous early growth.
✚ Large biomass.
HOW TO Spray off in early spring, unless destroyed by several ✚ Extensive strong root system.
DESTROY hard frosts (-5ºC). ✚ Late maturity.
✚ Frost hardy to -5ºC.
✚ C:N ratio 30.
✚ Very strong tap root will break through compacted soil. EVERGREEN
✚ Good scavenging and holding of nutrients within ✚ High biomass and dry matter
OTHER ✚ High resistance to BCN.
high biomass crop.
INFORMATION ✚ Very fast early growth, late maturity.
✚ Effective nematode reduction, variety dependant.
✚ Strong extensive root system.
✚ Non-host to clubroot. ✚ Frost hardy to -5ºC.
✚ Nematode reducing varieties.
8 Cover Crops Technical Guide
WHICH COVER CROP MIXTURE TO GROW?
Which soil issue is most important to resolve? What positive effects are you looking to achieve?
Poor soil structure, low organic matter/carbon levels, Reduce cultivation costs, boost soil fertility, help manage
high levels of blackgrass, high populations of harmful blackgrass levels, reduce pest pressure, long term soil
nematodes, risk of nutrient leaching and soil erosion. health improvements and farming sustainability.
Key considerations:
✚ What is your crop rotation? Avoid cover ✚ Will the catch/cover crop be used High C:N ratio covers crops will take
crops that may increase disease and pest for livestock grazing to produce nitrogen from the soil reserves as the
pressure in close rotations. additional income? soil biota starts the process of breaking
✚ When will you be able to drill the cover ✚ What type of drill will you use to establish down the carbon in the cover crop,
crop? Generally best growth/results come the following crop? which can restrict the amount of nitrogen
from early August sowings, choice of freely available in the early stages of the
✚ What is the likely Carbon:Nitrogen following crop.
species should change if September sown. ratio of the cover crop? The C:N ratio of
✚ How long do you want the cover to last? a species/mixture gives an indication of Low C:N ratio cover crops will conversely
Do you require a short term cover prior the speed of breakdown and release of break down much more quickly, making
to late autumn sowing, a longer term nutrients. This is important to understand nutrients available earlier, and returning
frost-susceptible mix which may save on as you may need to adjust your nutritional a greater percentage of the total within
destruction costs, or a full cover until the inputs to the following crop depending on the life-cycle of the following crop.
spring to maintain soil protection? when this occurs.
Cover Crops Technical Guide 9
AGRII SPECIALIST COVER CROP MIXTURES
STRUCTURATOR 1 N CAPTURE & FIX
Use in OSR-free or extended rotations. Use in all rotations. % Kgs/ha Seeds/m2
✚ Strong, diverse % Kgs/ha Seeds/m2 ✚ Brassica-free mix Black oats 50 9 45
rooting system Black oats 65 13 65 ✚ Diverse root types Spring vetch 20 3.6 6
✚ Creates a friable Oil radish 20 4 34 Crimson clover 12 2.16 43
✚ Captures and fixes
soil structure Phacelia 10 2 100 Berseem clover 10 1.8 60
nutrients
✚ Non-host for Asian radish 5 1 5 Phacelia 8 1.44 72
cereal diseases ✚ Medium biomass
Seed rate 20kg/ha 204 Seed rate 18kg/ha 226
✚ Medium/high biomass
Cover crop C:N ratio 35 Cover crop C:N ratio 24
STRUCTURATOR 2 ECO SOIL PROTECTOR
Use in rotations including OSR. Economic cover for all rotations.
✚ Strong, diverse % Kgs/ha Seeds/m2 ✚ Fast establishment, % Kgs/ha Seeds/m2
rooting system Winter rye 70 17.5 48 nutrient capture and Winter rye 80 28 76
✚ Creates a friable Oil radish 15 3.75 38 fix Vetch 20 7 12
soil structure Phacelia 10 2.5 125 ✚ Full season cover Seed rate 35kg/ha 88
✚ Clubroot resistant Linseed 5 1.25 18 ✚ Medium biomass Cover crop C:N ratio 35
oil radish
Seed rate 25kg/ha 229
✚ Medium biomass,
Cover crop C:N ratio 38
cold tolerant
All of the cover ✚ Mop up, hold and ✚ Suppress weeds The species and varieties used within the mixtures have been
crop mixtures fix nutrients ✚ Provide habitat specially selected to meet UK conditions, with particular emphasis
on these pages ✚ Reduce leaching for farmland on speed of establishment, maturity date and field performance.
should provide the ✚ Increase levels wildlife and
following benefits Seed size – thousand grain weight (TGW) is also an important
of organic matter improve farm consideration in species/variety selection, with the aim to reduce
to the grower, in and soil biota sustainability
addition to their variability which aids drilling and helps target the optimum plant
✚ Improve soil and income numbers per square metre.
specific uses:
structure
10 Cover Crops Technical GuideAGRII SPECIALIST COVER CROP MIXTURES
Solar Mixtures Designed to intercept the maximum amount of sunlight in order to increase carbon sequestration potential.
REGENERATIVE MIX CONSERVATION MIX
✚ Multi-species mix % Kgs/ha Seeds/m2 ✚ Multi-species mix % Kgs/ha Seeds/m2
✚ Diverse leaf canopy Spring vetch 30 7.5 13 ✚ Diverse leaf canopy Winter rye 30 7.5 20
to intercept maximum Black oats 24 6 27 to intercept maximum Spring vetch 30 7.5 13
solar energy Berseem clover 10 2.5 70 solar energy Oil radish 15 3.75 38
✚ Brassica-free Linseed 10 2.5 41 ✚ Nutrient capture Crimson clover 8 2 40
✚ Nutrient capture Sunflower 9 2.25 4 and fix Buckwheat 5 1.25 7
and fix Crimson clover 8 2 40 ✚ Varied root types to Linseed 4 1 16
✚ Varied root types to Buckwheat 5 1.25 7 stimulate soil biology Phacelia 4 1 50
stimulate soil biology Phacelia 4 1 50 and improve structure Berseem clover 4 1 28
and improve structure Seed rate 25kg/ha 252 ✚ Higher biomass and Seed rate 25kg/ha 212
Cover crop C:N ratio 22 carbon content Cover crop C:N ratio 30
SPRING CEREAL SOIL FERTILITY BUILDER FORAGE COVER CROP MIX
Non-cereal cover mix pre spring cereals on medium/light soils. ✚ Dual purpose mix % Kgs/ha Seeds/m2
✚ Cereal-free mix % Kgs/ha Seeds/m2
for arable and Winter rye 55 13.75 37
for light/medium livestock farms Spring vetch 20 5 9
Spring vetch 42 8.4 14
soil types Oil radish 20 4 40 ✚ Soil conditioning Stubble turnips 10 2.5 65
✚ Nutrient capture and forage Smart radish 10 2.5 20
Crimson clover 15 3 60
and fix production
Buckwheat 15 3 17 Phacelia 5 1.25 63
✚ Lower C:N ratio ✚ High biomass Seed rate 25kg/ha 194
Phacelia 8 1.6 80
✚ Medium/high Seed rate 20kg/ha 211 ✚ Nutrient capture Cover crop C:N ratio 38
biomass and fix
Cover crop C:N ratio 20
Seed should be drilled before the end of August to ensure good Bespoke custom mixtures are available from our
establishment and maximise biomass. Agrii Lincoln seed production facility, please enquire.
Adjust seed rates to account for soil conditions and drilling date.
Cover Crops Technical Guide 11ESTABLISHING THE COVER CROP
Key considerations:
TIME OF DRILLING PREVIOUS CROP ESTABLISHMENT
Many of the species require An important consideration TECHNIQUE
reasonable soil temperatures particularly if there are high Cover crops need good soil
and day length. Drill immediately after levels of straw residues; cover structure and a workable soil to achieve
harvest, ideally most cover/ catch crops crops could be held back and overall level maximum growth. Soil compaction needs
should be drilled by the end of August to of establishment will be disappointing. to be addressed both for the cover and also
give sufficient biomass and rooting. If following winter barley, then removal for the following crop, therefore subsoiling
of the barley straw would be useful, if not should be completed if required.
the straw and chaff residues need to be A subsoiler with a tine that stops large
SOIL MOISTURE LEVELS evenly distributed prior to drilling. amounts of surface disturbance should
Good seed/soil/moisture Very good establishment of cover crops be considered; again loss of soil moisture
contact is required to get quick has been achieved behind pea and bean is an important consideration.
emergence of the mixtures. Soil moisture crops, also after a fallow situation. Some species like mustard will grow
needs to be conserved and ideally effectively if scattered on the soil surface,
minimal soil disturbance should be however most are better drilled into the
considered during the sowing period. PESTS top 1-2cm and firmed with a roll.
Slug pressure needs to be
assessed following the previous
SOIL NUTRIENTS crop. If the pressure is high then slugs
To achieve a well grown cover need controlling before establishing the
crop, early nutrition in the form of cover crop.
nitrogen is required, depending on Pea and bean weevil can cause serious
previous cropping soil N reserves and problems for the vetches and clover
if there is a high level of straw residue, species, if the pressure is high and
approx. 20-30 kg of N/ha will be insect activity is causing damage the
required to aid establishment. appropriate insecticide should be used.
12 Cover Crops Technical GuideDRILLING THE FOLLOWING CROP
To maximise the benefit of the cover crop within the farm rotation, the following
areas need to be considered before establishing the following crop.
Key considerations:
TARGET CROP NUTRITION
DRILLING DATE The nutrient requirement of the following Cover crop residues with a
Have a target drilling date on which crop may differ to normal practice in higher C:N ratio will require more
to base your planning and operations. respect of application timing and amount N from the soil and therefore less is
used depending on the cover crop initially available to the following crop,
species within the mix. inhibiting growth.
DESTRUCTION OF The C:N ratio of a particular mix will Low C:N ratio residues including N fixing
COVER CROP determine the time it will take and how species will release excess N quickly
If the cover crop has not been much nitrogen will be required from the boosting early crop growth and reducing
destroyed by frost or grazed, you will soil N reserve to decompose the cover the overall N requirement.
need to consider the soil type and density crop residue and release nutrients to the The target is to maintain a crop residue
of the cover to determine when to spray following crop. This is because the soil covering the soil surface with a C:N ratio
off the cover in order to allow time for the micro-organisms require a C:N ratio of of between 25 and 30 to help maintain
soil surface to dry to aid drilling. 24:1 to work efficiently and maintain a a healthy living soil that will release
This could be up to 8 weeks on heavy healthy balanced soil. nutrients at a uniform rate.
soils with a dense cover crop.
DRILLING
PESTS Whichever type of drill you use to Excessive soil movement will
Assess the slug pest pressure establish the next crop, the aim is to move stimulate unwanted weed
before crop establishment, only the minimum amount of soil required germination and undo some of the
treat if necessary. to create good seed to soil contact. benefits gained from the cover crop.
Cover Crops Technical Guide 13OILSEED RAPE COMPANION CROPS
✚ Agrii has been trialling a range of companion crops Lifago buckwheat
for use with oilseed rape to assess their ability to reduce the
Lifago (F. Tataricum) gave the best results in field trials, although both
damage done by Cabbage Stem Flea Beetle (CSFB) and their
types were effective. Lifago has a unique combination of traits:
larvae as one part of the strategy to grow OSR successfully.
✚ Seed TGW, size and shape – allowing easier mixing, better seed flow
✚ Agrii trials have shown the use of buckwheat, when established
and lower seed rates.
well, reduced the damage to oilseed rape plants by the adult
CSFB during the establishment phase and continued to do so ✚ Plant development and structure – fast emergence, large leaf area and
through the autumn until the first cold nights when the buckwheat later flowering habit giving the OSR seedling more protection for longer.
died back. This extended period of protection reduced the number ✚ Cold susceptibility and phosphorus release – readily dies back and
of CSFB eggs laid on the OSR and importantly resulted in lower breaks down in low temperatures releasing nutrients to the
larvae numbers per plant in the spring. established OSR crop.
✚ It has also been noted in trials that OSR plots that had a
buckwheat companion crop appeared to be more vigorous Comparison of Esculentum and Tataricum buckwheat
and with an even growth habit in the spring. This may be
COMMON BUCKWHEAT LIFAGO
a consequence of reduced larvae damage or a benefit of its
phosphorus scavenging and release properties boosting the OSR.
✚ Having identified buckwheat as the best companion crop option
for OSR CSFB defence, we tested the species of buckwheat
available, Fagopyrum Esculentum and Fagopyrum Tataricum,
to identify the one with the best attributes and performance.
Lifago (Fagopyrum Tataricum) proved to be the best option (see Comparison of buckwheat seed
information opposite), although both types are effective.
F. ESCULENTUM LIFAGO (F. TATARICUM)
✚ In areas with low CSFB pressure and where soil structure and nutrient
building are more important then Tabor berseem clover and Bingo
purple vetch will help enhance establishment and crop growth.
✚ Companion crops should be used as part of the oilseed rape
establishment strategy, but not relied upon solely as the only
defence against CSFB. Please see the Agrii 8 Point Plan Typical TGW 28g Typical TGW 16g
for cultural control of cabbage stem flea beetle for more The lower TGW and shape of Lifago allows easier mixing with the
information: CLICK HERE OSR seed. Recommended sowing rate 10kg/ha with oilseed rape seed.
14 Cover Crops Technical GuideOILSEED RAPE COMPANION CROPS
Results of the oilseed rape trial at Langley, Essex. Adult flea beetle damage (scale of 1-9)
on 15th October & 8th November 2019
Assessment of the effect of using cereal stubble and 5.0
Lifago buckwheat as a companion crop, alone and in Elgar DK Exsteel
combination, in the reduction of cabbage stem flea
beetle damage in oilseed rape.
The trial shows a reduction in CSFB damage with
both treatments and the cumulative positive effect
when used in combination.
0
No buckwheat Buckwheat No buckwheat Buckwheat
Adult flea beetle damage (scale of 1-9)
on 15th October & 8th November 2019 No stubble Stubble
5.0
Elgar DK Exsteel Fresh weight (g) – 3rd April
4.0 180
160 Elgar DK Exsteel
3.0 140
120
100
2.0
80
60
1.0 40
20
0 0
No buckwheat Buckwheat No buckwheat Buckwheat No buckwheat Buckwheat No buckwheat Buckwheat No buckwheat Buckwheat No buckwheat Buckwheat
No stubble Stubble No stubble Stubble No stubble Stubble
Cover Crops Technical Guide 15Connect with Agrii
Via our At an Agrii Online at Follow us on Speak to our
Agronomy iFarm Event agrii.co.uk social media Seed Desk
and advisory We have 28 iFarm For the latest AgriiUK
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throughout the UK info@agrii.co.uk
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