Getting started with plant diversity

We know grasslands are important for producing quality forage, alongside carbon sequestration and supporting biodiversity, with choices to make which impact their performance from both economic and environmental perspectives, with one important choice the diversity of species.

Research has shown fields with a higher level of diversity can outperform ryegrass monocultures, but forage mixtures need not be complex. The benefits of increasing grassland diversity can be seen through enhanced animal performance and improved farm resilience and achieved by adding just one or two species to ryegrass.

The benefits of plant diversity

Greater grassland diversity supports increased soil health. This is primarily down to the different rooting activity diversity brings. Some species are deep rooting with a large tap root, while other species have fine root systems which explore a different area of the soil profile to the relatively shallow roots of ryegrass.

By having clovers in the mix, nitrogen is provided to the grass, allowing for a reduction in mineral nitrogen application particularly in the middle and the end of the season. And including herbs such as plantain supports better soil health by reducing soil compaction, and in particular surface poaching.

Herbs may also complement grass and legumes in the supply of minerals to livestock and work alongside wormers to reduce intestinal worms and the risk of wormer resistance, alongside benefits to dung beetle populations.

Soil organic matter can increase at a 30% higher rate in a multi-species ley compared to an equivalent ryegrass sward.

More organic matter increases soil health by allowing soils to hold more water, be more freely draining, and hold on to nutrients better alongside enhanced carbon sequestration.

Higher organic matter also supports a larger number of earthworms, which again allows for improved soil function and nutrient availability.

Grazing management

When species are added to fields, it is important grazing is managed to ensure the diversity persists. This involves grazing rotationally with stock moving every three days or less. This avoids overgrazing individual species and ensures the ley persists and performs over the long term. Diversity also enhances the cow’s diet, and if grazing isn’t managed, some species may be grazed in preference to others.

First Steps: Understand your farm system

• What is your soil type? Are you on light, medium or heavy soils? What is the pH? Not all species will grow on all soil types or climates. For example, there is a range of forage legumes which all capture atmospheric nitrogen, but some thrive in high pH soils (pH 7-8) such as lucerne and sainfoin, while others favour more acid soils (pH 5.5 – 7) including red and white clover, and birdsfoot trefoil. If you have a variety of soil types across the farm, you may need different mixtures for different fields.
• Decide what additional features you would like to gain from your grassland as this influences which species you select:
  • Are you trying to reduce mineral nitrogen inputs?
  • Do you need increased drought resilience?
  • How are your soils performing in terms of management?
  • Is the forage going to be cut, grazed or both? Some species are better suited to a cutting regime rather than grazing, so defining how the field will be managed is an important first step.
  • What age and grade of stock will be grazing the swards? The energy and performance requirements of the grazing stock need to be met by the species being introduced.

Phase 1: Field selection

Select a field where the ryegrass sward is not performing well as these are likely to be the conditions where different forage species will provide the most benefit. If you are unsure which species are right for that field, divide it in two and compare different options to your usual sward mixture. By starting with one field, it is possible to see how different species perform under your farm conditions and helps build confidence in how the swards suit your farm.

Phase 2: Weed management

Weed management can be a major hurdle to overcome when diversifying from a simple ryegrass sward although once established weed burden is often lower than expected in a multi-species sward because the mix of species is more competitive against weeds.

This effect occurs both above ground due to the various leaf types and below, due to the diversity of rooting habits. Because diverse swards improve soil health and reduce soil compaction, some weed species lose their competitive advantage.

In establishing a new sward, you may reseed with the diverse seed mix, but it is also possible to just sow grass initially to allow time for treating the weeds before stitching in the herbs and legumes once weeds are under control.

Many farmers find by using paddock grazing, livestock has a greater tendency to graze weed species, including docks. In a paddock system, topping any remaining weeds after grazing can reduce their vigour over the short and medium term.

Phase 3: Species selection

Each species provides a specific set of benefits to grassland:

And different species are suited to different types of management:

The two options for selecting multi-species seed mixtures are to add individual species to your existing ryegrass mixtures or trial an off-the-shelf mix and monitor what grows. It’s important to look at the range of species available and select for your specific conditions. See www.multispeciessward.co.uk for guidance on each species.

Phase 4: Establishment

WHEN: Some of the additional species need warmer soils to germinate than a ryegrass sward. Aim for establishment in late summer or late spring when soils are moist and warm, and just prior to further rainfall. Late summer establishment can be more reliable when avoiding drought conditions.

HOW: The seedbed needs to be fine and firm. Multi-species mixtures contain some very fine seeds, so good soil-to-seed contact is essential. To ensure good establishment, take particular care to sow at 5mm and to roll the seedbed twice prior to sowing and again afterwards.

GRAZING: A young multi-species sward benefits from a light graze for half a day 2 to 3 months after establishment to encourage tillering.

Set up a paddock system after the initial grazing: see Getting started with rotational grazing or ask your Area Manager for a copy of the ‘Getting started with rotational grazing’ guide.

Final point

Once you start testing different species in your swards you are likely to continue fine-tuning the contribution of individual species, adding or removing species based on your own observations and the livestock preferences.

For more on increasing the diversity of your grasslands, ask your Area Manager for a copy of ‘Getting started with plant diversity’ written by Farm Carbon Toolkit, the second of our Getting started guides.