Farmers with overwinter stubble as part of an ELS agreement may be wondering if these can be sown with a cover crop.

Unfortunately the ELS rules do not allow cover crops to be sown on most ELS overwinter stubble. The only exception is v.4 agreement holders who can sow cover on up to 5% of the stubble.

Derogations could be registered but

should be for one-off situations, not used routinely.

A well managed overwinter stubble, with lots of green material, as well as providing food and cover for birds in winter, will act as a cover crop. To ensure the stubble is rich in green cover, do not use a pre-harvest desiccant (ELS rules require this).

A very light surface cultivation, e.g.

stubble rake, may be necessary to break up surface capping/compaction and improve rain infiltration or to encourage weed germination in a bare stubble. This may stimulate some autumn mineralisation of nitrogen, and therefore increase the amount available to be leached, although some will be taken up by the growth of weed cover.

As part of the new requirements for Basic Farm Payment claimants from 1 January 2015, farmers with 30ha or more arable land need to have the equivalent of 5% of this land in Ecological Focus Areas (EFAs).

Cover and catch crops are one of the 5 EFA options available.

For this option farmers must use a sown mix of at least 2 different crops,

one a cereal and one a non-cereal. The current list of crops that can be grown are:

Mustard Oats Vetch Barley Phacelia Rye Lucerne

Alternatively, grass can be undersown in to the previous crop, particularly useful for late harvested crops such as

maize where it may not be possible to establish a sown mix after harvest.

Cover crops have to be established by the 1st October and retained until the 15th January. Catch crops have to be established by 31st August and retained until 1st October.

Catch and cover crops have an equivalence applied to them, so 1 ha of the crop = 0.3 ha of EFA.

Planning for Cover Crops: If you are thinking of including cover crops in the rotation it is important to

decide what you want them to achieve and plan accordingly.

1. Identify the beneficial properties you want to harness

2. Identify the cover crops that can do this

3. Based on the crops being sown identify the earliest possible sowing date,

seed rate, sowing depth and establishment method

4. Undertake early removal of grass weeds including cereal volunteers if

needed, and then let competition from the cover crop take over

5. Consider how cover crops sit with your rotation and whether they could

affect your disease management i.e. clubroot in oilseed rape

6. Check if the cover crops are eligible for greening

Winter Cover Crops and Greening

Cover Crops and ELS Overwinter Stubbles

Useful Contacts: Catchment Sensitive Farming: Poole Harbour: Charlotte Woodford: 07824 498959 Dorset Stour: Tim Stoner: 07500 071932 Hampshire Avon: Andrew Russell: 07901 512398

FWAG SouthWest: 01823 355427

NFU County Advisers: Dorset: Louise Stratton: 01305 231000 Wilts: Andrea Witcombe: 01722 441133

Wessex Water Catchment Advisers: Adrian Moore: 07500 033498 Louise Moderski-Rush: 07854 580910 Tim Stephens: 07823 370048

Winter Cover Crops—Advice Note This guidance note contains management advice on winter cover crops enabling you to

decide how they can benefit your farm business and where they can fit into your rotation.

Cover crops on bare land over winter offer benefits for soils, water quality, wildlife and the farm business. In groundwater catchments they are a crucial management option to help reduce nitrate losses, protecting drinking water supplies and our rivers and seas. They can also open up other beneficial management techniques such as minimum cultivation on heavier soils.

Benefits of Cover Crops:

For Soil:

Cover crops help to prevent soil erosion and run-off, keeping soil in the field

Deep-rooting crops will help to improve soil structure in compacted soils Cover crops build soil organic matter which improves soil structure and

water holding capacity helping to protect against extreme and prolonged rainfall and drought conditions

Reduce water-logging, and increase workability of heavy soils The presence of crops over winter sustains mychorrhizal fungi, and

maintains soil biota which promotes healthy soil biodiversity

For water quality:

Cover crops established early will put on a lot of growth, taking up nutrients, particularly nitrates, from the soil and prevent them from leaching through the soil profile, out of the rooting zone and into groundwater

The green cover intercepts rainfall, reducing surface capping, and taking up water which can prevent soil erosion and run-off over winter and reduce sediment and phosphate pollution to surface water

For wildlife:

The ground cover provided by the crops will provide shelter for wildlife over the winter months

The soil is likely to be richer in soil invertebrates, feeding birds and other wildlife over winter

Some early-sown cover crops can provide a late nectar source in mild autumns

Other agronomic benefits:

Can result in more friable soils, reducing the need for spring cultivations Cover crops that establish well provide competition to weeds, helping to

suppress them and reducing herbicide bills Cover crops also take up P and K therefore helping to maintain soil indices Mustard (in particular) contains glucosinolates which are released when

the crops are rolled, cut or incorporated, which mixes with a naturally occurring enzyme and water to produce a fumigant that can be deadly to weeds, soil-borne pathogens and nematodes

Can enable direct drilling on heavy soils where over-winter ploughing is current normal practice

Deep rooting crops can bring up trace elements from deep in the soil profile

Can result in healthier plants as a result of many of the factors above

Cover crops have wider benefits to the farm business:

Recycle nutrients making them available to the following spring crop, reducing the amount of fertiliser required, and/or increasing yields

Can reduce fuel use / draft requirement

Requires less machinery as enables wider use of minimum tillage

Can provide winter grazing More sustainable management of

soils protects the key asset on any farm, and looks after the foundation of the business

Prepared by FWAG SW and Catchment Sensitive Farming on behalf of the Environment Agency

Understanding What Cover Crops Can Do Why is nitrogen leached? Only some of the nitrogen applied to a crop is taken up and used. RB209 states that the average nitrogen use efficiency by crops by soil type is:

Light sand: 70% Medium and clay soils: 60% Shallow soil over chalk: 55%

This means that 30-45% of applied nitrogen is not used by the crop; and because nitrate is readily soluble and not strongly attracted to soil particles, it is vulnerable to leaching in the autumn and winter months when soil drainage occurs. The quantity of nitrate at risk of leaching is influenced by crop type, crop management, and crop N uptake during the autumn which reduces the soil nitrate content.

How much nitrogen do cover crops take up? Sowing date, variety of cover crop, weather and destruction date all affect the amount of nitrogen that is taken up by the cover crop. However, sowing date is key. August-sown cover crops take advantage of longer, warmer days to put on rapid early growth and develop an effective root system. Therefore they are much better than later sown crops at taking up lots of nitrogen before the leaching period begins. In addition, cover crops have more effect in mild, wet winters than in cold, dry winters, as in dry weather the nitrate is less likely to move out of the rooting zone by the spring. Therefore in light of climate change predictions of warmer, wetter winters, the need for cover crops increases.

What happens to the nitrogen taken up by cover crops? Some of the nitrogen will become available. Just how much depends on the rate of mineralisation, which is where the nitrogen in the plant material is converted to ammonium and nitrate. This happens fastest when the soil is warm and moist. Mineralisation takes place gradually between February and May and soil available N is greatest in April. The Carbon: Nitrogen ratio and the type of plant material also affects the rate at which mineralisation can take place. Nitrogen levels in cover crops that start to go to seed will reduce, so destruction date is important. Various studies suggest 10 - 50% of the nitrogen taken up by a cover crop will be available to the subsequent crop. The rest has a crucial role helping to build up soil organic matter, improving soil structure, water holding capacity and fertility, so essential to soil health.

How do I plan N fertiliser rates after cover crops? There is limited evidence currently available on how much N from cover crops should be taken into account when planning nitrogen fertiliser applications the following spring. Research shows that there is a yield benefit from cover crops which can help to offset establishment costs. Further work is underway and consider experimenting with a few tramlines to see for yourself the effects of modest nitrogen fertiliser reductions. ADAS trials indicate that many cover crops can provide 50 kg N/ha in the spring. This is worth approximately £38/ha

(based on Jan/Feb 2015 fertiliser prices) Agrii research shows that there is a yield benefit from cover crops in light soils at all fertiliser application rates Anecdotal reports are that on heavy soils there is no yield benefit but establishment costs can be reduced

David Johnson, Robin Hodgkinson, Eunice Lord, Martyn Silgram, Bruce Cottrill, Richard Gooday, Katrina Morrow, Sarah Smith and Adele Hulin. Nitrates Directive Consultation Document: The evidence base for assessing the impacts of the NVZ Action Programme on water quality across England and Wales. Source NIT18 Project

Average nitrate concentrations in winter leachate following different previous crops.

Nitrate concentrations in leachate with different cover crop sowing dates (SMN was similar for all sowing dates)

David Johnson, Robin Hodgkinson, Eunice Lord, Martyn Silgram, Bruce Cottrill, Richard Gooday, Katrina Morrow, Sarah Smith and Adele Hulin. Nitrates Directive Consultation Document: The evidence base for assessing the impacts of the NVZ Action Programme on water quality across England and Wales. Source NIT18 Project

Seed £/ha Fresh ton/

ha

Ton Dry

Matter/ha

% N

content

Kg N/ha

W. Turnip Rape 35 27.5 3.2 3.15 123

Oil radish top 45 29 2.9 4.76 140

Forage rye 97 17.9 2.3 4.6 105

Mustard 70 14.5 2.2 3.18 69

Stubble turnips 30 28.2 1.37 3.42 108

Catchment Sensitive Farming trials winter 2013/14 show the amount of nitrogen that different cover crop varieties took up.

Choosing the Right Crops - Why Grow Them? Choose crops providing the properties that are needed and suit local conditions:

Deep rooting crops such as radish will be beneficial where soil structural problems or drainage are an issue

Some crops, particularly mixes from continental companies, have low frost resistance so should be avoided in ‘frost pockets’

Some sensitivity to frost is useful to reduce biomass towards the end of the crops life and will aid incorporation

Legumes are not well suited to areas at high risk of nitrate leaching as the root nodules can break down over winter releasing N

Cereals could provide a green bridge for pests and diseases so think about whether this might impact on the subsequent spring crop

Forage rye grows quickly and provides an excellent root mass to bind soil together

Some varieties of mustard, radish and oats can help with nematode reduction

If growing oil seed rape, clubroot resistant varieties of oil radish are available

Fast growing cover crops that produce a lot of biomass such as fodder radish can be used to build soil organic matter

Buckwheat is effective at solubilising P and can help to build P levels in the soil

It is important to look at all of the establishment and management costs of growing cover crops, however once you place a value on the benefits they offer, most are cost-neutral.

Once the crop mixture has been selected, that will achieve the benefits required, see if they are eligible as an Ecological Focus Area as part of your Greening requirement.

If Greening is the driver for cover crops a simple mix including farm saved seed could suit many situations, but take advice from an agronomist on the best mix to suit the farm, its soils, and rotation. Under the Plant Varieties Act 1997, if using farm saved seed, ensure that all eligible varieties are declared to the British Society of Plant Breeders.

How to Grow Cover Crops To maximise the beneficial effects of your chosen cover crops it is essential to grow them well, sowing at the optimum time for the selected crops.

Seed rate: Sowing rate will vary considerably depending on seed size/TGW, sowing date and other crops in the mixture. Overall, the aim is for a thick crop and a high density of roots. Indicative seed rates: Mustard: 10 kg/ha Radish: 10-20 kg/ha Vetch: 40 kg/ha

Establishment: Most crops require sowing as early as possible, immediately after harvesting the previous crop, so August or September in most areas. This ensures that crops have at least 8 weeks of good growing conditions, which they need to establish well for the winter, and it also helps to minimise nutrient loss.

The appropriate sowing method depends on soil type and seed species to be sown. Aim to use a method that conserves moisture, and is quick and cost effective. Consider seed size and ensure mixes do not separate in the hopper.

Methods include: Direct drilling into the stubble Broadcasting and ring rolling Broadcasting into standing cereal crop Auto-casting from the combine Seeder unit on a cultivator

Depending on the crop grown and the

current season it may be appropriate to

apply a small amount (no more than 20

kg N/ha) of starter N at drilling. This will

ensure rapid development of roots that

will then be capable of accessing the

nutrients at the full depth of the rooting

zone. This could be an appropriate crop

to target with autumn applied manures

and slurries. Contact a FACT’s qualified

adviser for detailed advice.

Maintenance:

Most crops are problem-free but some potential management issues to watch out for are: Slugs Pests including flea-beetle and

sawfly larvae at the cotyledon stage Cereal volunteers acting as a green bridge

Destruction: Retain the cover crop until at least the end of January unless sowing a late-

drilled crop such as maize, when it can be left for longer.

Options for crop destruction are to graze, spray, flail or do nothing. The best option depends on crop, soil type and whether using the cover crop towards Greening.

Grazing or topping the crop in early January if ground conditions are suitable can help to reduce the volume of biomass to incorporate. Grazing also converts the nitrogen to a more available form as animal manure. Be aware cover crops used for Greening cannot be grazed until the cover crop period is over.

Winter cold will help to kill off cover crops, reducing the work needed in the spring. You can direct drill in to cover crops, typically after spraying off.

Calibrate seed drill to get correct seed rate

What’s growing below ground is as important as above