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Tuesday, September 21, 2021

Silvopasture Practices and Benefits

In agroforestry, silvopasture refers to the practice of bringing together livestock, forage, and trees in a single system. This is more complex than alley cropping, another agroforestry practice, which only brings together the elements of crops and trees. This isn’t simply the colocation of animals, plants, and trees, in that there is intentionality about silvopasture (Garrett, 2021). The three components are intended to be mutually beneficial (Judy, 2018). There are advantages and points of concern around this practice as well, which I will discuss here.

Before we can discuss what silvopasture is, we have to eliminate what it is not. Fully one-fifth of forested land in the United States is used for grazing. While it is a common practice in many parts of the United States for livestock to be set to graze on wooded public or private land (Garrett, 2021), simply having animals in an area with both forage and trees does not constitute silvopasture as a practice. Woodland pasture can be woodlots, areas with windbreaks, or non-industrial forests, and unlike in silvopasture there isn’t particular concern or attention paid to the health of the soil, care of the trees, or quality of forage (Orefice & Carroll, 2017).

There is a distinction to be made between silvopastoralism and silvopasture practices. The former is a broader category that includes both silvopasture and integrated forest grazing. The latter involves livestock being used as part of a plan to manage understory growth, harvesting native plants in order to improve the environment long-term (Garrett, 2021).

Silvopasture, on the other hand, is an interdisciplinary approach which seeks to make use of woodlands, forage, and livestock with a view towards profit, while also being concerned about the quality of the environment. Efforts are made in the design and implementation of silvopasture systems to ensure that the assortment of organisms involved can work together harmoniously (Garrett, 2021). It is possible, for example, for nitrogen-fixing plants like clover to enrich the quality of the soil for itself and also for other plants (facilitation), while walnut trees in an area release allelopathic chemicals which deter many other types of plants and trees from growing nearby (competition).

Silvopasture can put to good use land that would otherwise remain unproductive, such as rocky, sandy, damp, and hilly properties that aren’t fit for commercial commodity crops. At the same time, otherwise good land can be spoiled through incorrect grazing practices, harming trees and degrading soil (Garrett, 2021) However, there can be significant advantages to implementing a well-designed and implemented silvopasture practice, resulting in better protection of soil health and a more steady source of income (Judy, 2018).

Aside from land improvement benefits, the presence of trees that can provide shade and shelter can be beneficial to livestock. In inclement weather the trees can serve as a windbreak, and in intense heat they offer shade. In both situations the overall stress on the animal is reduced, lowering calorie burn and generally keeping them in a better state (Orefice & Carroll, 2017). There can also be a benefit to forage from the presence of trees, something I’ll discuss further below.

As I indicated above, more management is required in designing and implementing a silvopasture system than in traditional woodland pasture practices. Perhaps offsetting the increased effort is the possibility of silvopasture systems needing fewer external inputs, such as fertilizer, herbicides, and pesticides. In this case costs can be lower and there will be less dependence on outside suppliers . A mostly self-sustaining system can be realized.

Having such a system in place makes it possible to have a continuous supply of marketable products. Trees can produce nuts, for example, and of course cattle are themselves of value (Garrett, 2021). With a broader portfolio of product in a more sustainable system, risk can be reduce. Instead of banking on a single crop or the sale of livestock there can be a mix of products, providing some security. Traditional commodity crops grown in a monoculture can be considerably more susceptible to disease, infestations, and adverse weather conditions than a silvopasture system would be (Judy, 2018).

Two essential traits of a silvopasture practice are active management of tree density and shade, and careful attention to types of livestock and timing in order to maintain soil health and forage quality. Everything from root health to length of exposure to foraging animal, to the availability of light passing through the tree canopy need to be considered and reviewed on a regular basis (Orefice & Carroll, 2017).

As for initiating a silvopasture practice, there are two general approaches. In one, existing woods, such as woodlots, can be thinned. This is the fastest means to starting with silvopasture, but it requires the presence of mature trees to begin with. On established grasslands the longer route must be taken, which involves planting and protecting trees until they are of sufficient size to not be harmed by occasional contact with livestock (Judy, 2018). On this point some caution is required. Even in silvopasture systems with mature trees the animal presence must be monitored. While livestock are both “the product and the management tool,”, some types of livestock, such as goats and horses, can strip bark and injure root systems (Garrett, 2021).

When starting with an existing stand of trees some thinning may be required. Gary Judy (2018) suggests looking for the tree with the best trunk and crown and then harvesting the trees nearby, leaving it with less competition and the soil and forage more access to sun and rain.

On the other hand, when starting with a more-or-less ‘blank slate’ with an open field the possible interactions between trees and plants must be considered up front. If trees are planted into an existing pasture as-is, complete with grass and weeds, the competition for resources can potentially stunt the growth of the trees. Better instead to clear the field and plant trees and forage plants at the same time, and subsequently keeping weed growth down for the benefit of the trees (Garrett, 2021).

Shaded grass contains less lignin than that found in open fields. Lignin is indigestible for livestock, making shade-grown grass better forage (Judy, 2018). While forage grown in shade can be high quality, it is low quantity when compared to grass in open pastures (Ford et al., 2017). What makes the difference in a silvopasture system with regard to quantity and quality of forage yield is the sum of what takes place over the course of a year. High quality forage from shady areas, high quantity forage from sunny locations, and the tree by-products themselves (leaves, seed pods, etc) work together to provide a sustainable source of nutrition for livestock (Jose & Dollinger, 2019).

With good system design, implementation, and management a sustainable silvopasture system can be put into place. It may be more labor intensive, but requires fewer external inputs, potentially reducing cost. Livestock serve as weed control and process through digestion materials that are then returned to the land in the form of dung and urine. While adoption has been slow (Garrett, 2021), this practice is compatible with other traditional farming methods and provides benefits that will surely attract more attention in the future.

References

Ford, M. M., Zamora, D. S., Current, D., Magner, J., Wyatt, G., Walter, W. D., & Vaughan, S.
(2017). Impact of managed woodland grazing on forage quantity, quality and livestock
performance: The potential for Silvopasture in central Minnesota, USA. Agroforestry
Systems, 93(1), 67–79. https://doi.org/10.1007/s10457-017-0098-1

Garrett, H. E. (2021). North American Agroforestry: An Integrated Science and Practice (3rd
ed.). American Society of Agronomy.

Jose, S., & Dollinger, J. (2019). Silvopasture: A Sustainable Livestock Production System.
Agroforestry Systems, 93(1), 1–9. https://doi.org/10.1007/s10457-019-00366-8

Judy, G. (2018, March). The Benefits Silvopasture Provides for Your Farm. Stockman Grass
Farmer.

Lathrop, W., & Freking, B. (2018, July 24). Management Intensive Grazing. Kerr Center.
Retrieved September 22, 2021, from https://kerrcenter.com/publication/management-intensive-grazing/.

Orefice, J. N., & Carroll, J. (2017). Silvopasture—it's not a load of manure: Differentiating between Silvopasture and wooded livestock paddocks in the northeastern United States. Journal of Forestry, 115(1), 71–72. https://doi.org/10.5849/jof.16-016