Kevin Kelly with the award he received from the Support Iowa farmer organization on his work to establish vegetative buffers around livestock facilities through out the Midwest.  We have done work to establish vegetative buffers for livestock buildings in Missouri, Illinois, Indiana, Kansas, Nebraska, Ohio Minnesota, North Carolina, and Iowa.  Support Iowas Farmers has named KTF as a provider of advice and plant material, for people who want to do a buffer planting around any type of livestock facility.

Livestock buildingsUsing evergreens or deciduous trees to mitigate odors, stop blowing snow and keep excessive wind from livestock buildings.

Planting Austree Willows. around a hog facility.

Give us a call or E-mail and see what we can do for your operation. or 563-452-4300

The three pictures below is what we can do for you in 3 years.

Above is a hog building in Iowa just before we planted it.
We used 2 rows of potted austrees 5 ft tall spaced 8 ft apart in the row and 8 ft. between rows.  We are looking south in this picture.

Above is the result after 2 years, they are about 16 ft tall, and are already catching lots of blowing snow coming into the area.

Above, after 3 years of growth, we have trees about 25 ft tall, they are now catching all the snow and providing some real windbreak protection even in the winter.  The building has now “disappeared” from the neighbors if this is what you want and odors now are having to pass through the trees, slowing their progression into the landscape.

We do recommend setting the Austrees or outside row at least 80 ft from the building so snow will not drop on the building in a blizzard (see below). Also consider using 1 or more rows of evergreens on the inside of the Austrees for more long term snow, and wind protection and odor control.

Above is a row of Austrees only 45 ft from the hog building which is too close if you have several blizzards, the snow can drift on the roof and possibly cause problems.  The above picture shows an 8″snowfall with 40 MPH, think what would happen if we got several more snowstorms.  Austrees work great as a snow fence but keep outside row at least 80 ft from building, 100 ft is better.


The picture above is of Ryan Reed (left) of Ottumwa, Iowa, and his tree planting around his hog buildings that we helped design and supplied the trees for.  With their planting of trees and other things Ryan and Lana have done they were awarded the 2012 Pork Industry Environmental Stewards award.  Click on the below link to see pictures, article and video on what they have done to deserve this honor of a pork producer. Aerial picture shown below.

Using evergreens or deciduous trees to mitigate odors from livestock buildings.  Go to our site for more complete information.


Preliminary research and observations made by farmers suggest that shelterbelts placed around livestock production facilities may effectively reduce movement of odors emitted by manure to neighboring properties. Essentially, trees can be ‘put to work’ to reduce the movement of livestock production odors off-site.

Although the idea of placing treed windbreaks and shelterbelts around agricultural buildings and farm fields is not new, additional benefits from farm shelterbelts continue to be learned and tested. Shelterbelts alone will not prevent odor problems associated with intensive livestock production but may provide farmers with one more tool to help reduce negative visual perceptions and detection of smell by neighbors and surrounding communities.


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Figure 1. A single row of maturing conifers can significantly change the appearance of livestock production facilities and help filter out odor particles.

An odor-emitting source can include a livestock production barn, manure storage or a farm field where manure is being spread. Shelterbelts have the ability to reduce odor concentrations significantly at or very near the source, which greatly improves the effectiveness of separation distances.

There are five ways that treed windbreaks and shelterbelts can reduce the effects of livestock odor and improve visual perception of production buildings:

  1. Dilution and dispersion of gas concentrations of odor by a mixing effect created by shelterbelts
  2. Deposition of odorous dusts and other aerosols (like snow fencing) to the windward and leeward sides of windbreaks
  3. Collection and storage (sinks) within tree wood of the chemical constituents of odor pollution
  4. . Physical interception of odor particles (dust and aerosols)
    • Aesthetic appearance
    • Trees create a visual barrier to livestock barns
    • Trees can make cropped fields and pastures more pleasing to look at
    • Trees represent an ‘environmental statement’ to neighbors that the producer is making every effort to resolve odor problems in as many ways as possible

Dilution and dispersion

Without wind management, odors emitted from livestock facilities and manure storage areas tend to travel along the ground as a plume with air movement, especially during atmospheric inversions with little or no dilution of odor occurring.

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Figure 2. Without shelterbelts and without wind management, the odor plumes are picked up by passing air masses and travel near the ground with little or no dilution or filtration.

Shelterbelts create an obstacle for moving air masses. When designed properly, shelterbelts force turbulent fresh air up and over the tree row and will also moderate and evenly distribute a more gentle airflow through the trees. Less air movement past barns means less pickup and movement of odor off site.

It is believed that shelterbelts have the ability to lift some of the odor plume into the lower atmosphere where winds aloft mix and dilute the odor. The greatest dilution of odor occurs above and downwind from the quiet zone created by the action of wind passing over the shelterbelt. Beyond the quiet zone, more fresh air and less odorous air returns to the ground, thereby reducing movement of livestock odors off site.

Approximately 50 percent of the wind should be deflected up and over the shelterbelt and 50 percent should pass through the canopy of the trees. Two to five rows of spruce conifers spaced appropriately can provide an ideal 50 percent density (or 50 percent porosity) through the tree canopy. Shelterbelts are less effective for odor reduction when wind is absent but visual appearance remains in place.

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Figure 3. Shelterbelts located upwind and downwind of livestock facilities will reduce and manipulate air flow around the facility to reduce the spread of odors. Overhead winds can lift particles and gases into the lower atmosphere to help dilute and disperse odors. Also, more clean air diverts up and over the source of odor.

Shelterbelts create a ‘quiet zone’ of air that measures a distance of 8 to 10 times the height of the tree row downwind of the shelterbelt, and an additional moderation of wind speeds 10 to 25 times tree height, beyond the shelterbelt. Back-pressure created by the blocking effect of the tree row also creates a small quiet zone upwind of the tree line that is equal to 2 to 3 times the height of the trees.

Livestock barns and manure storage areas are best located in the quiet zone 75 to 100 feet downwind of shelterbelts. In addition, shelterbelts located downwind of the odor source are also important for filtering, absorption and trapping odors. Therefore, placing shelterbelts around the entire perimeter of livestock production areas is ideal. Shelterbelts should also be at least 75 feet from access roads and driveways to prevent snowdrifts from blocking farm vehicles during winter.

Deposition of odorous dusts

Shelterbelts create a physical barrier to wind and air movement. The trees absorb wind energy and reduce its speed near the ground. As a result, fewer dust particles and less odorous gases will be picked up by the air coming from livestock facilities. Also in calmer air, dusts and gases already caught up in the air will be more likely to settle back to the ground on the downwind side of the shelterbelt. This deposition effect is commonly seen with snow fencing where snow settles downwind of the fencing or trees due to reduced wind speed.

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Figure 4. Reduced wind speed in the quiet zone that is created downwind from a shelterbelt allows odorous dusts and particles to settle to the ground, similar to what happens with settling and drifting of snow.

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Figure 5. Shelterbelts located downwind of livestock production barns allow settling of odorous wind-borne dust particles. Shelterbelts should be located 75 to 100 feet away from barns.
To be most effective for deposition of odorous dust, shelterbelts need to be located upwind and downwind of odorous livestock facilities. Upwind shelterbelts reduce the quantity of dust and odor that is picked up by wind, and shelterbelts located downwind of the facilities are essential to reduce wind speeds to allow settling of odorous dusts that have become airborne.

For cropland, the same may hold true for reduction of odor movement where manure is being spread onto farm fields. Shelterbelts established around the full perimeter of farm fields should reduce movement of odor and can accommodate winds that are approaching the farm from any direction.

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Figure 6. Mature shelterbelts around cropped fields may help lift and disperse odors during application of manure as nutrient soil amendment, in addition to sheltering crops from damaging wind.

Studies of mass transport have shown that shelterbelts can remove 35 to 55 percent of dusts being carried in moving air which would provide a substantial reduction of offensive odors carried off-farm. The amount of dust that is picked up or allowed to settle will depend on wind speed, direction of the wind, density of shelterbelt trees, height of shelterbelt trees and number of shelterbelts.

Collection and storage of pollutant odors within trees (sink)

Scientific evidence of plant intake of livestock odors in field situations is limited, however there have been many studies done on the ability of plants to absorb air-polluting odors and chemicals. Research in livestock odor control shows very strong evidence that trees and shrubs of shelterbelts will help reduce odors. Trees and shrubs clean the air of micro-particles of all sizes by interception. Interception of air pollutants may be 20 times higher in treed or forested areas than non-forested cropped or barren lands. Conifers show a better ability to absorb air pollutants than deciduous trees.

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Figure 7. In air pollution research, odorous gases and particles can be absorbed into the foliage of conifers and deciduous trees during the growing season. Pollutants diffuse inside leaves and needles through tiny openings called stomata or adsorb into waxy coatings that naturally cover leaf surfaces.

Odorous gases, chemicals and dust particles can become fixed to plant surfaces and can enter into the plant tissue in three ways: 1) gaseous diffusion through open stomata, 2) on wet leaves, soluble air pollutants can enter through stomata in a dissolved liquid form, 3) pollutants can absorb directly into plant tissues.

Shelterbelt trees and shrubs absorb air pollutants when they are healthy and not under drought stress. Trees and shrubs absorb more air pollutants when leaf surfaces are wet. Higher humidity can increase uptake of air pollutants into trees, which is commonly measured within tree canopies.

Micro-organisms cover plant surfaces and there is evidence that these micro-organisms associated with shelterbelt trees also contribute to absorbing odorous chemicals. Forests are often referred to as pollutant air filters. This may also apply to shelterbelts trees.

Physical interception of odor particles

Trees are highly effective at physically intercepting dusts, gases and microbial particles that are carried in the wind. Shelterbelts are commonly used to catch spray drift of agricultural chemicals, reduce and catch pollen drift from agricultural crops, intercept and drop blowing snow and as barriers to trap blowing sand and soil caused by wind erosion.

As leaf surface roughness increases, the capture ability of particles and odor increases. Leaves with complex shapes (large circumference to area ratios) collect particles most efficiently. Therefore, conifers may be more effective at intercepting livestock odors than deciduous tree and shrub species. Conifers also have leaves (needles) year around.

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Figure 8. Like the air filters of home furnaces, shelterbelt trees, especially conifers, physically catch wind-borne odorous particles. Conifers have foliage year-round.

Shelterbelt design and planting

Selecting the species of trees and shrubs to plant will vary at each livestock facility and farm field site. Species selection will be based on the characteristics of each site including: soil type, natural drainage, common wind conditions, annual precipitation, natural range of each tree and shrub species and genetic preservation. If needed, advice of local experts can be sought such as experienced farmers and landowners, conservation authorities, tree horticulturists and foresters.

It is usually best to select several species of trees and shrubs for use in shelterbelts to prevent loss or destruction of the entire windbreak if attacking insect pests or tree diseases occur. Having diversity also offers a better chance for tree survival during alternating seasons of drought and wet soil conditions.

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Figure 9. Pleasing to the eye and to the rural landscape, shelterbelts comprised of diverse native tree and shrub species may help reduce negative visual perceptions associated with modern, intensive livestock production facilities.

Windbreaks may consist of one to three rows of alternating conifer and deciduous species while shelterbelts may be wider with more tree rows. Shrubs are generally planted in the outside rows, followed by conifers with deciduous hardwoods towards the middle or along the downwind side where they can grow more efficiently, sheltered from wind that is provided by conifers.

Ideally once established, the tree barrier should have a density of about 50 percent for best results for wind management. Conifers such as spruce will provide uniform branch coverage from the ground level up. Tree rows should be spaced wide enough apart to allow access by a small tractor for mechanized management of vegetation.

Weed management is important during the first five years of tree establishment using herbicides, or plastic or organic mulch. Weed management is important until the young shelterbelt trees have overtopped most weed competition and are free to grow.

Renovating old windbreaks

Maturing shelterbelts eventually begin to lose their ability to manage wind effectively as lower branches begin to die off and a percentage of trees are taken by diseases, insect pests, environmental stresses and natural mortality. Excessive holes in the tree row will enable wind to pass through without moderation. Wind management is eventually reduced or lost and farmers may need to renovate the shelterbelt. Renovation means ‘to make new again’ or ‘to restore to good condition’.

Some farmers choose to remove the old trees first and clear the way to plant new young trees. Others may prefer to establish new trees adjacent to the old trees and wait for the new windbreak to develop for several years before removing the old tree row. The advantage of overlapping the new and old windbreak provides continuous management of wind. Farmers may also decide that the tree row would be more effective if it is relocated, that is, re-established to a new site.

Other benefits

In addition to odor management, treed shelterbelts also act to reduce the seasonal cost of heating and cooling of farm buildings without disrupting ventilation in livestock barns.

Shelterbelts may also reduce the spread of specific infectious disease of livestock by blocking, intercepting or diverting wind-borne infectious organisms away from buildings.

Shelterbelts placed around farm fields reduce damage to forage and crops (preserve crop yield potential) caused by damaging turbulent winds while allowing normal air circulation to continue. Shelterbelts reduce soil erosion by wind. Around pastures, mature shelterbelts will relieve livestock of stress during hot summer days and cold windy winter conditions. Avoid planting trees and shrubs around livestock that are known to be poisonous.

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Figure 11. Road salt applied in winter can mist onto and kill shelterbelt trees. Colorado blue spruce and Austrian pine have some tolerance to the effects of road salt and can be used near highways.

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Figure 12. Where barns are surrounded by solid forest plantation, it is important not to block ventilation fans with excessive tree growth. Thinning the plantation and pruning off lower branches can improve air circulation. Fifty to 100 feet is a good separation distance between trees and barn.


J. Tyndall and J. Colletti. Literature Review on Air Quality and Shelterbelts: Odor Mitigation and Livestock Production. 2000. Forest Department, Iowa State University.

A. Knight and R. Walter. A Guide to Plant Poisoning of Animals in North America. Copyright 2001. Teton NewMedia. Jackson WY.