Conservation Grazing On Wilden Marsh
For many years I’ve watched Wilden Marsh flora growth and dieback cycles with increasing interest. I’ve seen lush green vegetation rise to heights of 3 metres and more, before the desiccating effects of winter sun and wind turn fibrous stalks and stems to dry, bleached and brittle standing skeletons that break from the host plant ending up on the ground as large-scale slow rotting litter – wind dried Himalayan balsam tubes and bulrush stalks are good examples of this. A small amount of organic ground littler can be beneficial on dry grassland because it will slow down moisture evaporation in times of prolonged drought and general short term dry weather, and it offers protection to invertebrates, but on the wet grasslands of the marsh we want organic matter decomposing deep within the wet soil and mud. On the marsh, unlike in dry ground, water moves up to the surface, or stays pooled in compartments for long periods, all year round in some cases, with many nutrients dissolved within it. Vegetation naturally dies back during autumn and winter, to regenerate in spring with the arrival of warmer weather and increased daylight. So when spring arrives, Wilden Marsh wakes up, seeds germinate and plants begin absorbing nutrients from the soil and their leaves combine sunlight with sugars to provide energy to fuel growth and reproduction cycles. Plants compete for as much life-giving sunlight as they can get. Ideally, to give new plant growth an early start, it’s beneficial to minimise ground litter – most of a plant’s energy is concentrated in the tips of its growth, so it needs to see the spring sunlight as soon as possible. Animals graze a plant’s tips first because of their sweet taste, and of course they are the most nutritious part of the plant. Even if we wanted to, it’s often not practical to mechanically scarify or rake marsh grassland to remove organic litter; however, we can minimise the amount of vegetation likely to fall on the ground to end up as litter by grazing it more effectively during and after the growing season.
On Wilden Marsh we have 92 acres, comprising of a 16.5 acres island and fifteen fenced and gated wet and dry compartments, requiring grazing throughout the year. The nutritional value of ground vegetation reduces as autumn and winter progresses. The cattle continue to eat old grass, reducing its height and bulk, enabling the ground to warm faster and new growth to receive early exposure to spring sunshine as soon as it arrives. The low nutritional value and scarcity of winter grazing results in the cattle loosing significant body mass.
When we put our nine cattle into a compartment and allow them to graze as they see fit, the first thing they do is eat the tastiest plant tips: the top 75 – 100mm. If there is Himalayan balsam in the compartment, they might eat this first, otherwise they will progressively reduce the height of lower succulent vegetation with successive passes. They might then become less interested in low vegetation and move on to taller and tougher plants like bulrushes, reeds, and willow; they pull individual stalks, leaves and branches down to get at the tastiest bits. In so doing they break the stems and trample them, which assists in their faster decomposition. It’s not a good idea to trample willow branches into the ground, though, because they will root and become saplings next growing season and trees within four to five years, but cattle don’t care about this.
The system we should use to greater effect is “mob grazing”: arguably similar to the way open range cattle grazed before intensive farming practices became the norm. Cattle progressively grazed, as a herd, continuously eating what’s in front of them, and they would probably not return to where they had started from until the following year – giving the grass plenty of time to recover. So we allow the cattle to graze a compartment just long enough to achieve the requirements of the plan, and then move them to another compartment. This system consistently puts vegetation in the front end of the cattle and evenly deposits four fifths of it as manure from their rear – if all goes well. The cattle are often well spaced when grazing a compartment and their small hooves are continually pushing organic matter deep into the mud; sometimes they graze as a tightly formed mob, which can cause a little poaching, but from a nature conservation point of view and the long time a compartment will be resting, poaching is not really a problem. The biggest risk from a bit of poaching is the potential for weed infestation. It is often not as simple and straightforward as it might at first appear, though: cattle might not want to eat certain plants, or they are grazing certain sections of the ground cover too low, and this is where polylines (electric fences) are useful.
We have a few very wet fields on the marsh where it might only be possible, because of seasonally high water levels, to graze a compartment once in a year for a two or three-week period, and these should be harder grazed than the drier and more accessible fields which might be grazed two or three times each year.
The grazing plan should depend on achievable goals and clear objectives, which in the case of Wilden Marsh are based around nature conservation needs. One of our aims is to attract breeding wading birds. Wading birds like muddy areas to feed in, and to breed they like very particular ground conditions. We have lapwing, snipe, curlew and red shank on the marsh, and these breed between mid March and mid July. Raised water levels are preferred between November through to mid February and low water levels from mid July until end of August. Grazing should be minimal between March and July inclusive, and intensive grazing from August to December inclusive. There should also be minimal interruption of the breeding grounds between March and July inclusive. It would also be a good idea to reduce rush cover between August and October inclusive. Any work associated with sluices, bunds and scrapes should be carried our during August to December inclusive.
As well as attracting waders, we have marsh flora requirements to consider, which also depend on reduced water levels during the growing season, so the requirements for waders and flora appear to be broadly compatible.
During June, July and August we keep the cattle away from compartments containing rare flora, because the cattle will eat them, so the herd is switched to weed control in less sensitive pastures. They spend their time eating Himalayan balsam, nettles, thistle and other low value plants that grow like wild-fire in the new pastures.
At the moment, the cattle are eating whatever takes their fancy in the Flooded Wood Pasture.