Managing manure is key to minimizing pen dust
Pen dust can be a significant issue for livestock welfare and worker health.
‘In Alberta, feedlot dust can develop during periods of prolonged dry weather,’ says Trevor Wallace, nutrient management specialist with Alberta Agriculture and Forestry. ‘While pen dust is not the only source of rural dust emissions (e.g., road traffic, feed yard and field activities), it is important that producers minimize pen dust because it can be a significant issue for livestock welfare and worker health, as well as a nuisance for neighbours.’
Dust from a feedlot is strongly influenced by weather and manure management. Wind, warm temperatures and increased sun exposure can rapidly dry out manure in feedlot pens.
Geographic regions experiencing low rainfall can see an accelerated manure drying effect. As daytime temperatures and wind speed subside, usually in the late afternoon or early evening, cattle activity increases, stirring up dust into the air above the pens. Without wind, dust tends to hang above the feedlot yard and can be extremely slow to disperse. These dust emissions peak into the evening, creating the greatest impact on livestock, staff and neighbours enjoying outdoor activities.
Feedlot pen dust is the result of dry, uncompacted manure, including bedding and soil, being pulverized into a fine powder by livestock activity and then being kicked up into the air by hoof action and wind. As warm, dry conditions reduce manure moisture content, it becomes more susceptible to being broken down into fine particles.
‘The most effective dust control method is to proactively remove manure before summer, and then monitor and remove any loose uncompacted material that accumulates over the summer,’ explains Wallace. Dedicating equipment and manpower may require extended effort but pen dust will become less of an issue.
‘Normally, we suggest the best approach is to scrape the feedlots by the beginning of June; however, every region is different. To monitor for low moisture conditions and dust potential in your area, you can visit the Alberta Climate Information Service (ACIS) webpage (https://agriculture.alberta.ca/acis/) to access near real time weather information and moisture situation updates.’
Secondary dust control methods, applying water to pen surfaces and increasing stock density, should only be considered after properly managing pen manure volume. These methods increase the moisture content of the manure, so it will not break down into a fine powder.
The most common methods of applying water include the use of water trucks, solid-set sprinklers and traveling gun watering systems. Applying water will not be as effective at controlling dust if manure volumes are not dealt with. In general, when more than 2.5 cm of uncompacted manure is present in pens, the water volume required to penetrate the manure profile is significant and cannot be practically applied without creating a wet surface. This can lead to pen floor damage and odour.
‘Weather will also affect water application efficiency,’ Wallace adds. ‘While it is more effective to apply water in the late afternoon, it may be too windy to do so properly. Alternatively, water applied in the morning or midday is wasted if evaporative demand is high. So before using water to control dust, it is a good idea to check the weather forecast.’
Another option involves increasing stock density, which helps increase pen moisture content by distributing manure and urine over a smaller area, minimizing the breakdown of manure. Wallace says that research suggests doubling the livestock density can reduce pen dust by up to 50%.
‘This practice also creates an exclusion area where any uncompacted manure collected during pen cleaning, could be stockpiled to ensure livestock do not disturb the pile and generate dust. Applying water and increasing stock density can be combined to reduce pen dust potential.’
He adds that if pen dust is not managed and results in repeated nuisance dust complaints, the Natural Resources Conservation Board may require a feedlot to have and implement a dust management plan.