Pasture management is a delicate balance of knowing when to graze, when to rest the grass, hoping for the sun, and then hoping for rain. Dearth is that frustrating point during the summer when your once green acres seem to suddenly dry out and fail to provide enough forage for your animals. No one likes to feed hay in the summer, but unfortunately that is exactly what many of us end up having to do. Perhaps you have noticed how the grass in the cool shade of a large tree stays green the longest, and is always more lush? Trees seem to stabilize their surroundings, mitigating the effects of sun and wind, and buffering the grass from the harshness of summer. Intentionally inter-planting pasture land with trees has come to be known as silvopasture, though there are many ways and degrees to which you can execute this strategy. The effect we see from this method is a combination of many factors; the most obvious and important being shade.
Here in Oregon it’s easy to think that the grass couldn’t possibly get too much sun; for heaven’s sake, 9 months out of the year we are wishing for sun with every fiber of our beings! But as it turns out, grass has a limited capacity for how much sunlight it can process every day. At a certain point, the plant cannot photosynthesize anymore, and the sun begins to stress and dry out the plant. Inter-planting your pasture with beneficial species of trees, spaced widely apart allows the grass to receive plenty of summer sun for part of the day, but protects it from overexposure. The potential delay of spring flush in these shady areas is more than outweighed by extension of the grazing season into the heat of the summer.
While most trees are beneficial to grazing systems to some extent, (excluding allelopathic species) deciduous trees allow vital winter and early spring sun to reach the grass, and should make up the majority of plantings. Deciduous trees provide seasonally appropriate shade, potential fodder, and added biomass to a pasture system, however, the occasional coniferous tree has its place. In spite of the more intense shelter requirements of some individuals in the winter, many animals do quite well under a mature dough fir or hemlock, especially in more mild climates. Having these islands of respite from winter weather, or intense summer sun greatly reduces stress on livestock and improves their quality of life.
Wind can also be a factor in maintaining soil moisture depending on your unique location, and while widely spaced trees may not exactly stop the wind, it can break up rushing winds and provide some protection for the pasture and livestock alike. In very windy areas dense hedgerows surrounding or bisecting a pasture can be much more effective at preventing drying out.
Another contributing factor to summer dearth is compacted soil, which prevents sufficient rainwater penetration and retention. Here again the root system of the tree works to break apart deeply compacted soils and create inlets for moisture, and biological interaction. Through transpiration, trees actually draw up moisture from deep within the soil below the reach of many grasses, and release moisture into their surroundings. Check out this article to learn more about how trees are able to bring moisture into their surroundings. The ‘edges’ created by breaking up a sea of grass with trees also increases plant diversity and microscopic biology, which promotes soil health and structure, all of which improves water retention.
Trees can be somewhat of an inconvenience to work around, and getting them established is extremely challenging with livestock continually trying to browse or molest them to death. Once a tree system is established however, it takes virtually no work to maintain mature trees. Ideally if you are clearing land for pasture you can leave strategically located mature trees in place which would prevent you from having to try to establish young trees, particularly in a pasture that tends to dry out without irrigation anyway.
A good starting place for planting trees where livestock can’t maul them to death is to plant along the outside of fence lines, or in corners where it is simple to put a small stretch of fence to protect the corner. For interior planting, running electric lines along each side of a row of seedlings and directly above can help keep cattle from trying to rub on and trample the trees. If goats are on your agenda, using t-posts and a ring of mesh fencing can work to prevent them from peeling bark, though this option is quite expensive and a lot of work if you are planting more that a few trees.
Another planting strategy is to select trees that provide a useful fodder crop to be harvested during summer dearth. Species that tolerate pollarding or coppicing are best. Planting these trees more densely allows the farmer to pollard (or ‘top’) every other tree on alternating years, so that a singe stand of trees provides both fodder and shade continuously. Dense plantings also make it less critical to protect the trees from livestock, if you just assume they will eventually kill a percentage and plant accordingly.
Though the concept of silvopasture has become fairly mainstream in recent years, I’m sure like many things us young farmers are just learning about, it was likely understood by mankind long before anyone ever thought to give it a name. Extending summer grazing, improving pasture health, and providing shelter for one’s stock are all incredibly valuable assets that in my opinion are worth the hassle of establishing a silvopasture system on your farm.
Check back for recommended species for your silvopasture system!