Vegetative buffers to control odors on livestock farms

Properly sized and positioned vegetative buffers are an effective odor control practice.

When spring approaches farmers’ thoughts turn to planting—planting crops, fruits, vegetables, pasture and harvestable forage. Livestock farmers may want to add an additional planting this spring: vegetative buffers, also referred to as windbreaks and vegetative environmental buffers.

Vegetative buffers control odors through five distinct mechanisms:

  • Lifting and mixing. Vegetative buffers lift the odorous air and dilute the odor compounds with fresher, less odorous air.
  • Settling. Some odorous compounds leave the livestock facility attached to dust particles. The slower wind speed caused by the lower levels of the vegetative buffer offer the ideal environment for these heavier particles to settle out of the air stream.
  • Filtering. Odor compounds and dust particles attach to the leaf surfaces of the vegetative buffer as the odorous air travels through the vegetation.
  • Breakdown of odorous particles. Bacteria living on leaf surfaces metabolize the attached odorous compounds.
  • Aesthetics. Trees distract a person’s eye and tend to soften the view of the livestock facility giving the site a more pleasing assessment and therefore the odor may seem less offensive.  

Effective vegetative buffers provide a continual line of vegetation with minimal gaps and skips between trees and shrubs. Iowa State University recommends that vegetative buffers have 40% to 60% porosity, meaning no more than 60% of the air space in the buffer should be non-plant air space. Because vegetative buffers gain height and density as they mature they can be thought of as an odor control measure whose effectiveness increases with age.

Vegetative buffers for odor control should contain a minimum of three species of trees and shrubs. A low-growing shrub will provide vegetation down to ground level. Second, an evergreen species will provide year round vegetation and odor control and a more permanent tree line. Finally, a fast-growing deciduous tree should be incorporated into the buffer to provide odor relief as soon as possible. A fourth row of maples or oaks (later-maturing deciduous trees), planted at the same time as the other three, will replace the fast-growing species when they are mature and must be removed. The schematic on the left provides a good illustration of a well-planned vegetative buffer for odor control.

Concern for the integrity of building foundations and manure storage structures suggests that vegetative buffers should be planted no closer than 75 feet to a structure. They should be no closer than 100 feet to naturally ventilated buildings to allow for uninterrupted air flow.

Some USDA-NRCS offices recognize vegetative buffers as a cost share practice. Interested livestock producers are encouraged to visit their local NRCS office for more information. Local conservationist will also be able to provide information on selecting the correct tree species to meet local soil conditions.

For more information and continued reading see Odor: Give Your Neighbors a Break – A Windbreak (see page 6) by D. Bolinger and G. May, and The Use of Vegetative Environmental Buffers for Livestock and Poultry Odor Management, by J Tyndall. 

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