Seed mix, seedbed quality and good weed control are key to establishing arable grass leys successfully.
Short term grass and clover leys offer many benefits to arable rotations, particularly for cultural black-grass control and improving soil quality and fertility.
But to maximise the benefits requires attention to details in five main areas, as Bob Bulmer and Stewart MacIntyre, of Hutchinsons, explain.
“A successful grass ley is primarily about choosing the right mix and sowing it into a really good quality seedbed which is consolidated well and kept weed-free,” says Mr MacIntyre.
1. Cultivations and preparation
A fine, well-structured seedbed with adequate soil moisture for germination is fundamental for grass and clover due to the small seed size.
Compaction, drainage or other issues such as weeds should be rectified before drilling and it is also worth checking soil pH and nutrient status.
Aim for pH 6-7 and phosphate and potash indices of 2.
Apply any additional fertiliser to the seedbed before or at drilling.
Livestock manures can be applied ahead of sowing to boost nitrogen, phosphorus and potassium levels, and improve organic matter.
Section 3 of the AHDB nutrient management guide (RB209) gives nutrient recommendations for grass and forage crops.
2. Selecting the right mix
Variety and mix selection depends on the purpose of he ley, for example, grazing, cutting, soil health, so use the AHDB Recommended Grass and Clover Lists to identify which are most appropriate for your situation.
Hybrid rye-grass is ideal for short to medium-term leys, while Italian rye-grass is also popular, especially where vigorous growth and large amounts of highly digestible biomass are required.
Adding nitrogen-fixing species such as red and white clover will help raise soil nitrogen. Lucerne is also of interest for its deep roots to improve soil structure.
Ideally there should be about five days’ difference in heading dates between different mixes to help ease management.
If the grass ley is sown as a mid-tier Countryside Stewardship option, follow the mix guidelines stipulated.
3. Sowing leys
Leys can be autumn or spring sown, however, the main window is mid-August to mid-September, often following winter barley. Competitive weeds such as redshank and dock can be bigger issues in spring sown leys.
For black grass control, early August drilling is preferred as black grass is less likely to germinate at this time, giving grass more chance to establish and outcompete weeds. Early September sown swards can sometimes be swamped by black grass.
Seed rates typically range from 18-35kg/hectare, with higher rates where establishment may be lower or to help outcompete weeds.
Small grass and clover seeds only need a fine covering of soil, so should be drilled just into the top 15mm. To maximise ground coverage and minimise the gaps between rows, consider splitting drilling over two passes, each at half rate seed, and at a slight angle.
Broadcasting is another option, although it may be harder to establish and even sward.
Consolidate seedbeds well after sowing to maximise seed to soil contact and retain moisture in dry conditions.
Slugs are the main threat when establishing grass leys in damp seasons, so monitor fields closely and treat where necessary.
Wireworm or leatherjackets can be a risk in reseeded leys after long term grassland (five-plus years), but there are no chemical controls available.
Weeds such as chickweed and docks should be controlled early with a suitable contact herbicide – there are no pre-emergence options. There are also very few clover safe herbicides, so consider this when planning seed mixes.
Black-grass is less likely to thrive in grassland where soil is undisturbed and where there is strong competition from the sward. Cutting or grazing regimes must be managed to avoid seed return, which could rule out growing for hay where black-grass is prevalent.
Grazing with sheep or young stock when grass reaches 7.5-10cm helps consolidate roots and promote tillering.
5. Returning land to arable
Leys established for black-grass control should ideally be desiccated using glyphosate before direct drilling the next crop to avoid bringing viable black-grass seed back to the surface. Timing depends on individual circumstances but good reduction in black-grass have been found form three to four-year grass leys.
Elsewhere, ploughing and cultivating in August or early September is often preferred ahead of following crops such as winter wheat.
Assess for shallow compaction caused by animal grazing and remove with shallow, low disturbance subsoiling if necessary.
There can be a 12-month delay before nitrogen sequestered in the sward becomes available to following crops, so consider following with a nitrogen fixing crop (for example, beans) rather than winter wheat.
Rye-grass volunteers may be an issue in cereals following grass leys, while couch can be problematic after long-term leys. There are no in-crop chemical options for couch, so this must be controlled with glyphosate prior to a crop being drilled.