Grassland Restoration – Gardening Backwards?

If we just do nothing to a field, a slowly changing mix of rank, dominant grasses with a matted under-layer of old dead plants will develop and, if left indefinitely, will develop as scrub and woodland. This may be fine in some areas, but we are assuming that we want diverse grassland habitats as well.

In a garden, if we want a range of different plants we try and provide the soil and other conditions which make for the most exuberant growth. A quick look at a gardening book or seed catalogue reveals that a depressing majority of plants seem to demand a sunny position with free-draining, nutrient-rich soils.

There are of course exceptions to this, but most gardeners struggle to give chosen plants the best of everything and, should they succeed, they then have to go out and attack the strongest to prevent them dominating the garden. Paradoxically, we might also fertilise a lawn and then mow it hard to preserve its uniformity and suppress 'unwanted' plants such as dock.

This is similar to intensive farming where grass is the crop. The farmer will kill off as many species as possible by ploughing, and then sow grass varieties that are particularly able to exploit high nutrient (fertiliser) levels. These varieties will dominate any other plants by their rapid growth and will be the first to recover after cutting.

So how should we proceed? Gardening tells us that most (but not all) plants will do really well given sufficient water and rich and well structured soil which is not too acid or alkaline. This is also true of many grassland plants seen in herb-rich traditional meadows and pastures and would suggest that if we increase nutrient levels and improve drainage we should see more flowers and a greater diversity of species on our land. But this is part of what the intensive farmer does to produce the green deserts that are so familiar!

In fact, restoration of grassland is almost conventional gardening in reverse. The first thing we try to do is reduce the soil's nutrient levels. This may seem illogical – we have already said that many of the plants we want to encourage can do well on rich soils. The factor missing from this equation is competition. Whilst most species that we want to encourage will do very nicely if on their own in rich soil, others, such as agricultural rye-grass, can do even better, tending to swamp the rest and preventing establishment in the first place. Yet the species we want to encourage will grow perfectly well under much poorer conditions and have an edge over the greedy agricultural types! (It should be pointed out, however, that many 'traditional' grass species such as cocksfoot can dominate fields on rich soils and there is nothing intrinsically wrong with rye-grass; it's lack of variety that is the villain of the piece.)

Thus we must change the soil conditions to give less vigorous species a chance. We must also enable seed to get to the soil and to germinate and can encourage additional species if we allow or create wetter areas by impeding drainage.

Fortunately, there is a simple way of both reducing nutrients and encouraging seed to germinate. This is by making hay fairly late in the season and not putting on fertiliser or manure to replenish the nutrients we remove. By late July and August, many wild plants will have set seed. For many, the ripening process can be finished by cutting and drying in the field. During this period the hay is repeatedly kicked about by machinery and much of the seed present will be shed. In contrast, silage making usually involves several cuts from early in the season, before little or no seed has set, and most modern silage harvesting machines effectively sweep the field clean of plant material and much other wildlife.

Hay cutting may be followed by 'aftermath grazing' later in the year in order to remove some more nutrients and open and tread the sward (turf) to help new plants establish from seed. If the land is too rough or wet to permit hay making, grazing stock may be the only way to remove nutrients, but this will be a relatively slow process.

The nutrient levels will continue to fall in succeeding years and the dominance of the more vigorous grasses will become reduced. There will be a few more species established from seed each year and these plants will in their turn set seed. And so the process can continue year by year as seed is introduced from other areas by wind, birds or small mammals. If the land is suitable, drainage can be impeded to further suppress agricultural grasses and provide opportunities for more wetland species to become established and increase overall diversity.

There has been no use of 'wildflower seed' at Denmark Farm. It has become increasingly clear that this was probably a wise decision by the Taylors in the 1980s since not only have most of the more desirable species arrived of their own accord, but the communities seem better balanced than many of the sown fields found elsewhere. There have been successes on other sites where locally gathered old meadow seed has been available, but in all too many instances unbalanced communities of plants with alien strains from abroad have resulted from sowing of commercial seed mixes.

After about five years of this treatment, the greedy rye-grass will usually have been reduced to a minor role with some combination of bent-grasses, fescues, sweet vernal-grass and crested dogstail dominating the sward. The yellow flowers of cat's ears and hawkbits should have appeared and as time passes and fertility falls still further, legumes such as trefoils and red clover become apparent. Plants which partly feed off the grasses (hemi-parasites) can also invade and help reduce grass dominance still further. Yellow rattle and eyebrights are the most familiar of the latter and their spread can be spectacular.

Over perhaps ten years of persistent nutrient depletion, the hay yield will fall to about a third or less of previous levels. However, the removal of fertiliser bills and re-seed costs from the equation can help offset reduced productivity.

Just how long should this process be continued? At some point it will be sensible to re-introduce grazing as a significant part of the management cycle. This will help diversify the vegetation structure which will benefit many invertebrates and vertebrates. The breed(s) used for grazing together with stocking rates and timing will all affect the sward development and this is a whole subject in itself. However, as a rather sweeping generalisation, cattle and horses will usually produce a more diverse sward than sheep, but the choice of breed and local conditions are always significant.

As with almost anything in agriculture and conservation, fixed rules cannot be defined for grassland restoration. The 'best' course of action will always be the product of basic principles applied in the context of conflicting demands and local conditions. However, it is amazing what can be achieved by simply stopping the more obviously destructive activities. As has been shown at Denmark Farm, this can rapidly result in enriched grassland ecosystems, and supporting these by creating other diverse habitats can multiply its effectiveness.