Catch crops and cover crops guide

In recent years, we have seen renewed interest in the use of catch crops in Ireland. Also known as cover crops or green manure, catch crops have a role to play in the regulatory requirements for green cover under the GLAS (Green Low-Carbon Agri-Environment Scheme) rules.

However, the increased interest is more about farmers’ desire to use them to improve crop productivity and soil structure.

There are different options available in terms of the species or mixtures that can be used as catch crops. In this guide, we aim to explain the requirements under GLAS and examine the benefits of growing catch crops.

We also explore the suitability of various GLAS cover crops and mixture options for different requirements. We hope you will find this guide useful for discovering the different types of catch crops when planning an effective programme for GLAS.

Contents

1. The benefits of catch crops
2. GLAS Payment
3. Greening Payment
4. Mixture options
5. Catch crops examples
6. Management of catch crops

The benefits of catch crops

Catch crops are planted to reduce nutrient leaching from the soil following the main crop. The crop then scavenges available nitrogen and other nutrients.

Cover crops are grown to provide “green” cover to the soil. Cover crops will help prevent soil erosion while also suppressing weeds. Some cover crops can also reduce the incidence of pests and diseases.

Green manure crops are those that are sown into the soil to improve and condition it, while also releasing nutrients. In this guide, we will refer to all of these as catch crops.

GLAS Payment

Catch crops are an important part of both the GLAS Payment and Greening Payment schemes. If participating in either, it is important to comply with the rules – please click on the links for further information.

The objective of the GLAS scheme is to establish a catch crop that will absorb nutrients and prevent leaching in the autumn/winter period.

• Catch crops must be sown annually by 15 September
• Use a mixture of at least two crops from the list of prescribed crops
• Light cultivation techniques must be used for sowing – ploughing not permitted
• Must remain in place until 1 December
• Grazing of not permitted before 1 December

The following is the list of prescribed crops permitted in the GLAS scheme and the sowing rates:

Greening Payment

Catch crops can play a very important role in fulfilling Greening Payment obligations.

1. As an Ecological Focus Area (EFA)
2. When grown in GLAS under equivalence, they negate the necessity for crop diversification (there is a reduction in the GLAS catch crops payment in this case)

The catch crop mixture must contain at least two species from the list of prescribed crops. The list is the same as those prescribed under GLAS.

However, the seed rates are not specified but should be similar to the seeding rates within GLAS.

Mixture options

Regardless of whether or not you are participating in the GLAS or Greening schemes, catch crops offer multiple benefits to improve soil condition in arable situations.

At Germinal, we have designed a range of catch and cover crop mixtures to comply with GLAS and Greening rules, while also bringing multiple benefits to your soil.

When sowing catch or cover crops, it is important to remember:

• Sow as early as possible (prior to 15 September for GLAS/Greening requirements)
• Ensure you select from the list of prescribed crops
• If you have a brassica in your arable rotation (e.g. oilseed rape), do not use a mixture containing a brassica
• Do not allow crops to set seed (weeds in future crops)

We recommend you select one of the following mixtures when sowing your crop:

Soil Booster Pro (1.5 ha pack)

21 kg: Vetch 18 kg, Phacelia 3kg

Vetch is a popular option to quickly provide green cover and fix Nitrogen. It is particularly good at competing against weeds. With good frost tolerance, it can maintain a canopy over the winter.

Phacelia is very quick to establish and produces a large root that helps improve soil structure. Soil Booster Pro is an ideal option where oilseed rape is in the mixture as radish or brassicas could be problematic.

Key benefits

• Fast establishment
• Nitrogen-fixing
• Improves soil structure
• Suited to rotations containing oilseed rape
• Suppress weeds

Soil Booster Max (1 ha pack)

25 kg: Vetch 19 kg, Tillage radish 5 kg, Phacelia 1kg

Soil Booster Max provides rapidly growing green cover that will help condition the soil and reduce erosion. The vetch will fix atmospheric nitrogen and boost the overall performance of the cover crop mixture.

Meanwhile, the Phacelia will grow rapidly and quickly provide green cover while helping to reduce nutrient loss from the soil. Phacelia is a good example of a cover crop that will condition the soil and improve soil structure by helping to increase air movement and improve drainage.

Tillage radish will scavenge nutrients from lower down in the soil and bring them to the upper layers, where the next cash crop can utilise them.

Key benefits

• Quick establishment
• Nitrogen-fixing
• Nutrient scavenging & reduced nutrient leaching
• Soil conditioning
• Reduces erosion
• Suppress weeds

Soil Booster Plus (2 ha pack)

20 kg: Tillage radish 10 kg, Forage rape 6 kg, Phacelia 4 kg

Soil Booster Plus provides rapidly grown green cover to condition the soil and reduce erosion. Phacelia will swiftly offer green cover while helping reduce nutrient loss from the soil.

Tillage radish will condition the soil and improve soil structure by helping to increase air movement and improve drainage. The taproot will also help scavenge nutrients from lower down in the soil and bring them to the upper layers where the next cash crop can utilise them.

• Key benefits
• Rapid establishment
• Nutrient scavenging
• Reduces nutrient leaching
• Soil conditioning
• Suppress weeds

Soil Booster Graze (2 ha pack)

16 kg: Leafy turnip 10 kg, Forage rape 6 kg

Soil Booster Graze will scavenge nutrients, condition the soil and can also be used as a forage option for grazing animals after 1 December.

A rapidly growing mixture that will quickly establish green cover, Soil Booster Graze reduces nutrient leaching and conditions the soil by improving the structure through drainage, aeration and reducing erosion.

Soil Booster Graze will provide a valuable high-energy feed for winter grazing of cattle and sheep. Animals will require constant access to water and a fibre source such as silage if grazing this mixture.

Key benefits

• Rapid growth
• Soil conditioning
• Improves soil structure
• Reduces nutrient leaching
• Supress weeds
• Suitable for grazing after 1 December

Catch crops examples

To simplify your selection process, we have developed a star rating to indicate the suitability of each catch crop to conventional Irish conditions.

We have taken into consideration that the crop will not be sown until late summer/autumn, the potential benefits of the crop, the price and availability of the crop and its suitability to Irish growing conditions.

In some cases, the recommended sowing rate will be higher than the rate outlined due to the method and timing of sowing. Below you can find suitable examples of catch crops.

5★ = suitable as a catch/cover crop in Ireland

1★ = less suitable as catch/cover crop in Ireland

Forage rape: 5★

This can be grazed after 1 December as a forage for cattle or sheep. Rapid growing ability with good winter hardiness, Forage rape is a high-energy feed for grazing ruminants.

• Sowing rate: 3-5 kg/ha
• Frost tolerance: Good
• Biomass: Good
• Pests and diseases: Generally, not a problem, but clubroot could become an issue if brassicas are used as a cover crop over a period of years

Tillage radish: 5★

A deep-rooting plant that extracts nutrients from down in the profile and helps open channels in the soil for subsequent crops. Tillage radish improves water movement and drainage and increases airflow through the soil.

• Sowing rate: 5 kg/ha
• Frost tolerance: Poor – frost will help decay tillage radish and thus avoid the requirement for chemical spray
• Biomass: Will generate large biomass quickly
• Pests and diseases: Generally, not a problem, but clubroot could become an issue if brassicas are used as a cover crop over a period of years

Mustard: 3★

Mustard is a rapidly growing annual that will help reduce nitrogen leaching and suppress weeds.

• Sowing rate: 6-10 kg/ha
• Frost tolerance: Low, but this helps in its incorporation as it will be largely diminished over
• the winter
• Biomass: Good
• Pests and diseases: Generally, not a problem, but clubroot might become an issue if brassicas are used as a cover crop over a period of years

Leafy turnip: 5★

Leafy turnip is a member of the brassica family with high early vigour. Their deep rooting will help condition the soil and relocate nutrients from the subsoil to the top. It will also help reduce nitrogen leaching.

• Sowing rate: 5 kg/ha
• Frost tolerance: Good
• Biomass: Yields of 3-5 t DM, suitable as a forage crop
• Pests and diseases: Generally, not a problem for a leafy turnip, but clubroot could become an issue if brassica is used as a cover crop over a period of years

Oats and Black oats: 3★

Oats and black oats can provide cover over the winter to help reduce soil erosion due to good tillering capacity. Oats have poor winter tolerance and are easily killed and worked back into the soil. Useful for weed suppression and as a nurse crop with hairy vetch.

• Sowing rate: 75-100 kg/ha
• Frost tolerance: Poor
• Biomass: Reasonable
• Pests and diseases: Generally, not a problem

Peas: 1★

Peas have good nitrogen fixation abilities and can be sown as a nitrogen-fixing crop in an area declared as an EFA. Generally, peas are not suited for sowing after a main cereal crop as it is too late in the season for them to establish.

• Sowing rate: 30 kg/ha
• Frost tolerance: Poor
• Biomass: Good if sown early in the season
• Pests and diseases: Generally, not a problem

Beans: 1★

Beans, like peas, have excellent nitrogen fixation abilities and can be sown as a nitrogen-fixing crop in an area declared as an EFA. Beans are not suited for sowing after the main cereal crop as it will be too late in the season for them to establish.

• Sowing rate: 90-100 kg/ha
• Frost tolerance: Poor
• Biomass: Good if sown early in the season
• Pests and diseases: Generally, not a problem

Hairy vetch: 5★

Hairy vetch, a forage legume also known as Winter vetch, has superior winter hardiness over Common vetch and is very suitable for sowing as a cover crop due to its ability to fix nitrogen at lower temperatures than many other legumes.

This can also be used as arable silage with grass or as a whole crop mix combined with cereals. Vetch will help increase the protein content in the mix.

• Sowing rate: 12 kg/ha
• Frost tolerance: Good winter hardiness
• Biomass: Rapidly produces a large biomass
• Pests and diseases: Generally, not a problem

Common vetch: 4★

Common vetch is suitable for sowing as a cover crop because of its ability to fix nitrogen and suppress weeds due to its ability to rapidly form a canopy.

• Sowing rate: 12 kg/ha
• Frost tolerance: Good winter hardiness
• Biomass: Rapidly produces a large biomass
• Pests and diseases: Generally, not a problem

Forage rye: 3★

Extensive and deep rooting, forage rye is excellent for soil conditioning. Effective at reducing nitrogen leaching and soil erosion over the winter.

Forage rye is also suitable for grazing in early spring. It provides a flexible sowing option after maize/cereals and can be grazed or zero grazed.

• Sowing rate: 65-80 kg/ha
• Frost tolerance: Good winter hardiness
• Biomass: Good
• Pests and diseases: Monitor at establishment for leatherjackets, slugs and frit-fly. Generally, not a problem once established

Crimson clover: 2★

Clovers have excellent capability to fix nitrogen at soil temperatures above 8°C but are less effective over the winter period.

Crimson clover is suited to earlier sowing in July/August to maximise warmer temperatures. Quicker to establish than longer-term clovers. Ideal for usage as green manure for soil improvement.

• Sowing rate: 10-15 kg/ha
• Frost tolerance: Good
• Biomass: Good
• Pests and diseases: Monitor at establishment for leatherjackets, slugs and frit-fly. Generally, not a problem once established

Berseem clover: 2★

This short-term annual legume is referred to as Egyptian clover. It can establish quickly and produce biomass when sown at suitable temperatures.

Berseem clover can be used as soil-improving green manure. Some work has shown that it can be used as a companion crop in oilseed rape.

• Sowing rate: 10-15 kg/ha
• Frost tolerance: Sensitive to Frost
• Biomass: High biomass potential
• Pests and diseases: Generally, not a problem

Squarosse clover: 3★ (not GLAS approved)

This annual clover can withstand temperatures of -10°C at its rosette stage. Squarosse clover grows upright with a thin taproot and many branches. It can produce a lot of organic matter and is good for soil structure.

• Sowing rate: 10-15 kg/ha
• Frost tolerance: Very winter hardy
• Biomass: High biomass potential
• Pests and diseases: Generally, not a problem

Balansa clover: 3★ (not GLAS approved)

This is an annual clover noted for its winter hardiness when compared to other annual species such as Egyptian and Persian clovers.

Balansa clover can establish quickly and produce biomass when sown in suitable warm conditions, much like the other annual clovers. Balansa clover has unique top growth along with a large taproot, making it a species option worth looking at.

• Sowing rate: 5-8 kg/ha
• Frost tolerance: Very winter hardy
• Biomass: High biomass potential
• Pests and diseases: Generally, not a problem

Phacelia: 5★

Phacelia is a rapidly growing crop, which will reduce nitrogen leaching and suppress weeds, with a beneficial root structure.

• Sowing rate: 2-5 kg/ha
• Frost tolerance: Poor
• Biomass: Lower biomass than many other cover crops, but it works extremely well as part of a mixture and the recommendation would be to sow it with other crops
• Pests and diseases: Generally, not a problem

Buckwheat: 2★

Establishing quickly and helping suppress weeds, buckwheat is a fast-growing crop which will help reduce nitrogen losses.

Buckwheat is good to scavenge phosphate in the soil, which it can make available for subsequent crops after incorporation.

• Sowing rate: 30-40 kg/ha
• Frost tolerance: Poor
• Biomass: Good
• Pests and diseases: Generally, not a problem

Management of catch crops

Rapid establishment of catch crops following harvest will ensure there is adequate moisture for germination before stubbles dry out from lack of cropping cover.

When to sow

Spring or autumn are the best times to grow catch crops. In autumn, the earlier they can be established the better, to make use of longer days and warmer ground temperatures. Every day counts once the cereal crop is harvested.

How to sow a catch crop

Drilling a catch crop as soon as possible after the cereal harvest keeps the soil active all the time. The leaching of nitrogen is minimised and the organic matter that will be incorporated into the upper soil is maximised. Crops can be drilled directly into stubble or broadcast onto cultivated ground.

Since all mixes contain a combination of small and big seeds, a sowing depth of 1.5-3 cm is recommended. Rolling is important to ensure good soil-to-seed contact and help maintain soil moisture for germination and growth.

Fertiliser

Farmyard manure/compound fertiliser could be applied prior to cultivation/drilling to provide the growing plants’ basic nutrients. This will maximise growth and subsequent biomass for grazing or cover for overwintered crops.

Nutrients applied will be taken up by the growing catch crop and released upon breakdown in the spring to the following cash crop. Where sown as a Greening requirement, minimal fertiliser if any is recommended.

However, if intending to graze the crop, applications of nitrogen and phosphate are essential to increase yield.

Incorporation of crops

Generally, temperatures over winter in Ireland are not low enough to kill the crop, so it is recommended to burn them off with herbicide or cut with a flail mower.

Incorporation can then be done by ploughing or rotavating. After burning off, the catch crop can be incorporated by discing and the cash crop can be drilled in.