Silvopasture is a technique that falls under the Agroforestry umbrella. It is a system of managing for two products from the same piece of land – forage (pasture) and trees. The trees may be primarily meant to provide fruits, biomass, or lumber – or, in some cases, additional forage. It can be accomplished in one of two ways – thinning woodland to encourage better light penetration and thus better growth of pasture species OR planting trees into established pasture.
The benefits are numerous. The combination improves conditions for both products. The light/dappled shade reduces evapotranspiration, heat stress, and drought for the forage species. The ground cover of forage species reduces soil temperatures, reduces compaction, and increases organic matter in the soil. Organic matter increases water holding capacity and is a slow-release source of nutrients. Studies have also shown the combination of the two sequesters a greater amount of carbon than either does alone. A third benefit is for animal health. Especially with increasing temperatures due to climate change, the shade and the evaporative cooling reduces heat stress on the grazers.
I am using the second approach and planting black walnut (lumber), bur oak (biomass/firewood), black cherry (lumber), hickory x pecan hybrids (fruits), and elms (forage). The first 4 are pretty straight forward but the last – the elms, may require some explanation. During my dissertation research I learned that in many parts of the world elm leaves/branches are used to feed livestock during winter or periods of drought where herbaceous plants dry up or are fully consumed. Elms do not have toxins in their leaves like some oaks and cherries do. There are some folks that claim black walnut leaves and nut hulls help control intestinal worms in livestock, which would be a bonus.
One challenge of combining the two is that brome grasses, common forage species – exude compounds that inhibit tree germination and growth, a process called allelopathy by biologists. I’ve experienced some VERY slow growth and high mortality – especially from the hickories.
A second challenge in managing the system is to get the trees large enough not to be endangered by browsing by the animals pasturing in the area. I am using tree tubes to protect the saplings until they get a sizable crown above nose level. The tree tubes I use have been designed to have ventilation to ensure trees go dormant as appropriate with falling temperatures, summertime heat stress is minimized, and humidity that can encourage fungal proliferation is not elevated. I will also be caging the young trees, probably with welded wire fence cylinders stabilized by t-posts until the trees produce mature bark.
