Advice on adding herb species to a grazing reseed

Walking grazing fields to identify plant species when they are in growing and flowering mode will establish which clovers and herbs are naturally occurring on the farm.

Reseeding costs can then be reduced by only adding in those species that are missing (using a herbal seed mix), to qualify for an environmental scheme or enhance a farm’s resilience. 

This is according to agricultural consultant Luppo Diepenbroek of Straight Line Nutrition.

He suggests seeking help from a Natural England adviser to select species that are specific to a farm’s geography and soil type. 

See also: Top tips on tailoring herbal leys to upland farms

“Plantain naturally occurs on British farms; dandelions are also classed as a herb, and cows and sheep eat them – so you have got two herbs [to start with].

Other herbs I have seen on livestock farms include selfheal – found on heavy land in Devon – sorrel and comfrey,” says Luppo.

© Farlap/Alamy Stock Photo

Ploughing consequences

Learning from early adopters of the Sustainable Farming Incentive scheme in England (now closed to new applicants), he reveals that too many farms ploughed up permanent pasture to drill herbal leys.

This released carbon to the atmosphere, buried nutrients and organic matter, and probably brought up weed seeds.

It may also have added to seed costs by sowing herbs that were already growing in fields, thus losing good farm biodiversity, he says.

Luppo suggests that a pasture walk in a W-shape across a field, avoiding compacted gateways and poached areas (as for soil sampling), could help with reseeding policy.

Ideally, this should be carried out between mid-July and mid-August.

“Look for the percentage of ground cover of grasses, clovers and herbs according to leaf area. Ideally, there should be one-third of each,” he explains, pointing out that clover coverage needs to be at least 30% to fix the equivalent of 180kg N/ha a year.

Because herbs die down over winter, it is important for their distribution to be even across a grazing field.

“Patchy coverage means that when plants die back in winter, it leaves open ground for weeds to invade, such as docks and thistles,” he adds.

Pollinators and palatability

Although environmental schemes pay farmers to grow flowering herbs to attract pollinator species such as bees and butterflies, Luppo thinks farmers should also choose palatable species to improve livestock performance from grazing.

“Herbal leys make more resilient swards and a more resilient farm – droughts are getting closer together.

“By increasing plant biodiversity with more deeper rooting species, it will help you get a couple more weeks of grazing in summer, so you don’t need to make and feed more silage and could save up to 250kg/ha of nitrogen,” he says.

Establishing a herbal ley, however, requires different techniques to a grass sward. A typical autumn reseed is timed to catch rainfall to help with germination.

Clovers and herbs have very small seeds that are best established through minimal soil disturbance – overseeding, not reseeding, says Luppo – and no later than mid-August, to ensure soil temperatures are still warm enough.

Grass starts growing at soil temperatures of about 5C, but clovers and herbs need 9C.

Furthermore, newly established seedlings need to be grazed off before winter to promote tillering and ground cover.

Rotational grazing to promote herbs

Plantain ribwort © Adobe stock

Grazing management in a rotational system can be adapted to encourage herbs and clovers to flourish, flower and set seed by operating grazing rounds longer than 30 days, says Luppo.

However, he cautions that plantain and chicory can take over and make up two-thirds of the sward.

“Weather can drive herbs to overtake the grasses because, in a dry spell, a plant under stress sets seed for survival. Grasses won’t germinate in dry weather, but chicory and plantain do.”

Instead, he suggests the best method is to repair any field damage, then oversow on fields with 50% bare ground.

This counteracts allelopathy, where some plants release chemicals that hinder the growth of other species, effectively stealing nutrients from new seedlings.

Best conditions are after a silage cut when ground is open. Use a grass harrow to create a tilth and broadcast seed.

Be careful if applying via the fertiliser spreader when going over bumps or potholes in the road, as this separates out the seed.

Use a rooting compound to encourage new seeds, then ring-roll into the ground in a criss-cross manner to push the seed in and create channels for moisture to get to it, he explains.

First grazing

“You will see new herbs within two weeks if it rains after sowing. Then the first light grazing can be four weeks later.

“If you can pull out a seedling by the roots, cut it. But if it holds well into the soil, then use young [light] cattle to graze it.

“Lambs and sheep are selective grazers, eating the most palatable leaves, so if you use sheep, make sure they just have a quick walk across the field, then out.”

Patience is essential with herbs. There is little to see in the first 12 months, says Luppo.

“It takes time for establishment; after two years, you will see one-third coverage, then reassess the field and see how it is.”

Comfrey © Adobe Stock