Making the best use of cover crops
Cover crops can provide nutritious winter forage for livestock as well as improving soil health. Chloe Palmer reports.
There has been increasing interest in cover crops as a method of improving soil structure, retaining nutrients between crops and adding organic matter. Now a few farmers are starting to look at whether cover crops could also provide valuable grazing.
Jake Freestone is farm manager at Overbury Enterprises on the Gloucestershire-Worcestershire border, where sheep and cereals, particularly wheat, are the main enterprises.
After completing a Nuffield Farming Scholarship in 2014, Mr Freestone looked at how livestock and arable could be more closely integrated at Overbury. He was already growing cover crops across much of the cropped land and grazing them was an obvious next step.
Species mix sown at Overbury this year
- 25kg/ha of rye
- 10kg/ha of vetch
- 3kg/ha buckwheat
- 2kg/ha berseem clover
- 1kg/ha phacelia
- Total seed rate: 41kg/ha
- Cost: £39.25/ha
In 2014, Mr Freestone drilled 14 cover crop mixes, looking at the yield data from each crop and measuring the metabolisable energy (ME) and crude protein levels. This data allowed him to develop the best mixtures to provide the ideal ration for ewes grazing the cover crops.
He says: “We now grow a mixture of vetch and rye, adding small amounts of buckwheat, berseem clover and phacelia, and we find this makes a beautifully balanced ration for ewes.
“Ideally we are aiming for an ME of 11-13MJ/kg dry matter and CP of 20 per cent.”
Drilling the cover crop as early as possible is vital to ensure there is sufficient growth to allow for grazing, says Mr Freestone.
“We literally go straight in with the no-till drill after the combine to allow us to grow enough of a crop for the sheep. We may need to spray off with a little glyphosate if the stubble is weedy.”
Benefits to livestock of grazing cover crops
- Makes use of the cover crop to generate an income
Can provide highly nutritious forage at a time of year when the feed value of grassland is limited
Allows for resting of grassland over the late winter months, resulting in the availability of fresh grazing in the run-up to lambing
Provides clean grazing, reducing the worm burden
It is possible to sow a bespoke cover crop species mix to provide desired levels of metabolisable energy and crude protein content. n Some species will also contain higher levels of micro-nutrients and trace elements
Mr Freestone admits choosing the best technique when seeking to graze cover crops was a process of trial and error in the early days, but the system is now working well for both livestock and the arable operation.
“We put our mid-pregnancy ewes on to cover crops after Christmas. We mob graze them in groups of 400-500 across fields of five to six hectares (12-15 acres), grazing them for five to six days before we move them to a fresh field.
“This works for us at it means we have a smaller number of individual groups to check. The higher stocking rate for short periods means ewes will tread the plant material into the ground which helps our objective of increasing organic matter in soils.”
Mr Freestone has not experienced any issues with bloat and even when offered grassland to run back onto, he says the ewes usually choose to stay on the cover crop.
“The ewes seem quite content and they do not wander. We were surprised; even when a small amount of mustard was included in the species mix they still chose to eat it off.”
Jake Freestone’s top tips for grazing cover crops
- Choose the species mix carefully. Consider the nutritional value and palatability of the species along with the farm’s soil type, timing of sowing, climate and the subsequent crop
- Fencing should be mobile and easy to erect
- Think about how water will be made available to livestock. Bowsers should be sited so they can be moved easily without causing rutting and compaction. Where possible, locate on a track with a pipe to trough if required
- Cover crops will need to be established early if sufficient growth is to be available to graze by livestock
- Consider allowing livestock the option of running back to grassland or make straw or haylage available so animals can maintain fibre intakes
What to sow: Choosing the right species mix for the system
Ian Wilkinson, owner of Cotswolds Seeds, believes cover crops should not be thought of as ‘stand-alone crops’ but should be viewed as an integral part of the rotation.
Not grazing them is a missed opportunity, he says.
Mr Wilkinson says no one size fits all, but rather the choice of species must be carefully thought out to achieve the best outcome.
He offers the following suggestions for species commonly included in cover crops:
- Legumes will increase the protein content of a cover crop and can provide a firm base, leading to a reduced risk of poaching
- Legumes are excellent for building soil fertility and can help provide some of the nitrogen required if grown with fodder brassicas in the cover crop. They also allow cover crops to support more animals for longer, adding more manure to the soil
- Including 2.5kg/hectare (1kg/acre) of a clover species is usually sufficient and white, crimson clover or berseem clover are useful additions
- Adding a small proportion of grass is helpful as it will increase palatability and give a resilient under layer to the cover crop
- Choosing fast growing species, such as Italian rye-grass, is recommended, adding up to 7.5kg/ha (3kg/acre) to a mixture
- Avoid including too much phacelia in cover crop mixtures for grazing as it is a hairy, unpalatable plant which will be avoided by sheep, although it can provide nectar and pollen late into the season
- Brassicas provide large quantities of feed value in winter. If yielding well, they typically produce up to 4.5t DM/ha (1.8t DM/acre)
- A typical early fold root mixture containing stubble turnips and forage rape will cost just £18/ha (£7/acre). An area of 1.2 hectares (three acres) of it is capable of producing up to 45t/ha (18t/acre) with 10 per cent DM in about 10-12 weeks, which can provide 100 sheep with sufficient keep for a month
- Brassicas are hungry for nitrogen and good scavengers, but need 70kg N/ha to achieve their full yield potential. If required, this is best applied as an application of farmyard manure prior to sowing