Value of vegetative buffers quantified

Work in the US has identified plant species that are particularly beneficial in trapping poultry house emissions.

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One of the experimental layouts using Norway spruce and hybrid poplar.
One of the experimental layouts using Norway spruce and hybrid poplar.

The use of vegetative buffers – single or multiple rows of shrubs and trees – can significantly reduce odours, dust and other factors impacting the immediate environment around poultry farms, studies from Penn State University have shown.

The university’s Department of Poultry Science has been quantifying the degree to which various plant species can help address a number of “nuisance” factors. These factors are a natural part of the poultry grow-out process, and vegetative buffers can not only reduce them, but also improve farm aesthetics.

Dr Paul Patterson, a leader in the project, notes that investing in foliage and landscaping around poultry farms can pay multiple environmental dividends to growers. They can beautify the landscape by providing a visual barrier for operations, preventing neighbours from being exposed to routine activities, such as feed deliveries and the loading and unloading of birds.

“At least equally important,” Dr Patterson notes, “vegetative buffers can also help address a number of issues relating to poultry farm operations that nearby residents, particularly those new to the rural areas where poultry tend to be located, sometimes complain about.”

Professor Patterson’s work has broken new ground in demonstrating the variety and effectiveness of vegetative buffers as tools to help meet some of the challenges facing the poultry industry when producing in more populated areas.

Careful choices

The climate of Pennsylvania is diverse due to the multitude of geographic features found within the state. Sitting between two major climate zones, the southeastern corner of Pennsylvania has the warmest climate. Moving west toward the mountainous interior of the state, the climate becomes markedly colder.

The plants that were used in the trials had multiple zone tolerance and were grown in the cooler part of the state prior to being utilized on farms in the warmer areas.

Research at a Penn State hen farm recorded a 67 percent reduction in total levels of particulate matter (PM) at a distance of 20 feet downwind from a five-row vegetative buffer, with important differences in the types of plant species used.

The team observed differences in the species planted, with willow capturing the fine PM2.5 and less of the intermediate sized PM10 than juniper vegetation. Associated research showed that spruce and hybrid willow were effective traps for dust and its associated odours.

In Pennsylvania, to reduce the potential for community conflict, new and expanding poultry and livestock farms are required by the state to develop an odour management plan and submit to an odor site index.

Scoring high values on the index requires farmers to implement specific, and often costly, Best Management Practices (BMPs) required by the state. According to the Poultry Science Association, studies by Dr Patterson’s team have shown that appropriate use of vegetative buffers can help to reduce odors and associated index scores.

Further benefits

In a September 2008 study, Dr Patterson’s team measured a 46-54 percent reduction in odour levels as a result of the use of a buffer comprising 50 fir, juniper, willow, ornamental pear and birch trees, when compared to odours without trees present.

The studies have also demonstrated that vegetation can help trap ammonia emissions emanating from poultry houses. The amount of foliage needed to “scrub” emissions will depend on the size and type of facility. The species used in the ammonia studies included Honey locust, Hybrid poplar vegetation, Reed canary grass, and Norway spruce.

“Native plants are generally a good choice when planning a buffer, but there are many imports that performed well in our evaluations, for example the Aus Tree, an Australian hybrid willow, that is quick to establish  and fast growing,” Dr Paterson says. “Another non-native grass that we have been impressed with is the Miscanthus x giganteus grass, which is very tall, quick to establish and good with trapping dust and odour.”

The work has also shown that vegetative buffers can be effective in reducing infectious bronchitis transmission via wind, between birds on the same or different farms. The additional benefits of vegetation do not stop there, however.

“In addition to improving farm aesthetics and lowering dust, odour and ammonia levels, shrubs and trees can also help hold down energy costs,” Dr Patterson notes. “Strategically placed, these buffers can act as snow fences, dropping snow in from of the buildings instead of on the roof or around access roads, feed bins, or fans.

“Other vegetation can be planted to shade the radiant load of summer sun on buildings to cool the air entering the inlets or curtains. Investment in appropriately selected and sited vegetation around poultry farms really can yield a surprising number of benefits.”

Buffers can also be processed for bedding material or utilized as a biofuel, and some species will be better suited to these purposes than others.

There have been concerns that vegetative buffers can act as a harbour for wildlife. Dr Patterson says: “The vegetation could be harborage for rodents and wild birds. While we have not witnessed this to be the case, we are monitoring the situation. One farm that monitors rodents weekly, has caught one mouse in two years with a very aggressive trapping and rodent control programme.”

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