The Green Low-Carbon Agri-Environment Scheme (GLAS Scheme 2022) and Greening rules are driving demand for catch crops (also known as cover crops or green manure). Germinal grass and forage expert Niall Laffan sheds light on how best to use catch crops under Irish conditions.
Examples of catch crops
Niall explains: “Catch crops work by scavenging nitrogen and other nutrients available in the soil and holding them in place during the autumn and over winter. Some crops also provide cover for the soil (hence the name cover crops), helping to reduce weeds and soil erosion.
“Introducing a variety of root structures improves soil drainage, and the additional organic matter supports overall soil health. Some catch crops can also provide low-cost forage in the later winter months (from 1 December onwards), and they all contribute to pest and disease management.”
Germinal’s four catch crop mixes comply with GLAS and greening rules and offer all the soil health and nutritional benefits described above:
| Species included | Rapid establishment | Soil conditioning | Reduce nutrient leaching | Increase soil organic matter | Suppress weeds | Fix nitrogen | Control nematodes | |
| Soil Booster Pro* | Phacelia Vetch | Y | Y | Y | Y | Y | Y | |
| Soil Booster Max | Tillage radish; Vetch; Phacelia | Y | Y | Y | Y | Y | Y | Y |
| Soil Booster Plus | Tillage radish; Forage rape; Phacelia | Y | Y | Y | Y | Y | Y | |
| Soil Booster Graze** | Forage rape; Leafy turnip | Y | Y | Y | Y | Y |
* Brassica-free so ideal for use where a brassica is being used in an arable rotation
** GLAS participants can graze after 1 December
Sowing catch crops
“The sooner you can establish catch crops after harvest the better, as more sunlight and warmer ground temperatures help with establishment.
“Catch crops can be drilled directly into stubble or broadcast onto cultivated ground. The variety of seed sizes within a mix means a sowing depth of 1.5-3 cm is recommended, and rolling is crucial for good seed-to-soil contact.
“If sowing a catch crop under Greening requirements, ideally no or minimal fertiliser should be applied. Where it is intended for grazing, applications of N and P are essential to increase DM yield.
"Typically catch crops are not killed off by winter temperatures in Irish soils, so it is recommended to burn them off or cut them (after 1 December) before incorporating by discing. Don’t allow catch crops to set seed as it can cause weed problems in future crops.”
Using catch crops for GLAS Scheme 2022
The general guidance for using catch or cover crops under GLAS is:
- Catch crops must be sown by 15 September
- Use a mixture of at least two crops from the specified list – see below
- Ploughing is not permitted – use light cultivation techniques only
- Catch crops must remain in place until 1 December
- Grazing catch crops is not permitted before 1 December
The specified crops required to meet the GLAS Scheme 2022 and greening obligations are the same but there are some differences between the two schemes. For details of all the requirements, click here.
Prescribed catch crop seeds and their suitability for Irish systems
All the prescribed catch crops are available from Germinal as straights in addition to the Germinal Catch Crop Mixtures. Their individual benefits, species type and suitability to Irish conditions are outlined in the table below:
| Catch crop | Benefits | Sowing rate kg/ha | Type | Suitability for Irish systems |
| Forage rape | Fast-growing, high-energy forage for cattle and sheep | 3-5 | Brassica | 5/5 |
| Tillage radish | Deep roots improve soil structure and drainage | 5 | Brassica | 5/5 |
| Leafy turnip | Deep roots act as a good soil conditioner | 5 | Brassica | 5/5 |
| Mustard | Fast growing and suppresses weeds | 6-10 | Brassica | 3/5 |
| Common vetch | Fixes nitrogen and rapidly produces a large canopy able to suppress weeds | 12 | Legume | 4/5 |
| Hairy/Winter Vetch | Better winter hardiness than common vetch. Increases protein content of arable silage | 12 | Legume | 5/5 |
| Peas | Nitrogen-fixing crop able to be sown in an Ecological Focus Area (EFA) | 30 | Legume | 1/5 |
| Crimson and Berseem/Egyptian clovers | Nitrogen-fixing and quick to establish. Suitable as green manure | 10-15 | Legume | 2/5 |
| Beans | Nitrogen-fixing crop able to be sown in an Ecological Focus Area (EFA) | 90-100 | Legume | 1/5 |
| Oats/Black oats | Cover reduces soil erosion and suppresses weeds. Works well with hairy vetch | 75-100 | Cereal | 3/5 |
| Forage rye | Deep and extensive roots condition soil and reduce erosion. Suitable for grazing in early spring | 65-80 | Cereal | 3/5 |
| Phacelia | Fast-growing crop with a beneficial root structure. Works best within a mixture of cover crops | 2-5 | Other | 5/5 |
| Buckwheat | Quick to establish and suppress weeds. Good phosphate absorption | 30-40 | Other | 2/5 |
| Squarrose clover* | Crop producing a large amount of biomass, good for soil structure | 10-15 | Legume | 3/5 |
| Balansa clover* | Quick to establish in warm conditions, producing a deep tap root | 5-8 | Legume | 3/5 |
* Not GLAS approved
Niall concludes: “With a good range of catch crops or cover crops available under GLAS and Greening, you can pick the right one for your system. For bespoke advice, contact our grass and forage experts or learn more about the different types of catch crops by using our Catch crops guide.”