Controlling Feed Yard Dust
As the afternoon sun begins to wane, the particulate matter in the air is apparent. A cloud of dust particles hangs over the pens of cattle, from the ground to about 20 feet in the air. The air is stagnant. And the dust is thick. Cattle cough and their eyes water. It’s a time known as EDP, or evening dust peak.
Hot and dry summer conditions at feedlots can often lead to periods of increased dust. According to the University of Nebraska, some of the worst time for dust to develop is during the late afternoon and at dusk, when temperatures begin to drop and wind speed decreases. Cattle that have mostly been resting during the hottest part of the day become more active. The day’s sun has dried out the earth, and the increased activity in the pen creates dust that hangs in the evening air.
Excessive dust can cause problems with animal health, worker conditions and annoyed neighbors. A dust abatement plan can feature several methods of integrated management.
Manure harvesting is critical to controlling dust. Studies confirm that dust potential grows with the increasing depth of uncompacted manure. “The fundamental reason appears to be that cattle characteristically drag their rear hooves across the corral surface,” according to a 2012 AgriLife publication. “Dragging the rear hoof accounts for most of the mechanical shearing that resuspends the manure as particulate matter.” The article goes on to recommend cleaning pens regularly to maintain a 1- to 2-inch surface layer of well-compacted manure and soil.
Although pens are commonly cleaned when cattle are shipped, the article recommends monitoring pen conditions and removing the uncompacted surface layer of manure before it gets too deep, even if animals occupy the pens.
Optimizing moisture content of the surface manure is very important for dust abatement. This can be done with sprinkler systems, water trucks or wagons or traveling sprinkler systems. The goal is to maintain moisture content of the surface manure to 25 to 35 percent. Studies found that sprinkler systems reduce downwind particulate matter from 55 to 80 percent.
Water treatment should begin before dust becomes a problem, according to retired agricultural engineer John Sweeten’s publication Feedlot Dust Control. “The moisture can be raised to the desired level initially by a heavy water application or by animal crowding,” he states, “followed by a daily water sprinkled treatment program.”
Sweeten recommends adjusting water application rates according to weather conditions, animal size and manure depth. His recommended initial application rate is 1 gallon per square yard per day (approximately .18” per day) until a 25 to 35 percent moisture is reached. Then water can be applied at ½ to ¾ gallon per square yard per day (about 0.09 to 0.13 inches per day) during dry weather.
California research showed dust levels rose more than 850 percent when water treatment was discontinued for seven days, so consistency is key. In fact, the research determined daily watering provided significantly better dust control than alternate day watering.
The unmistakenable “wet” feedlot odor is always a concern, but Sweeten says the key is the amount of water applied to the surface. “A moisture content of between 25 and 40 percent is required for rapid aerobic bacterial activity, which produces little unpleasant odor.”
However, overwatering leads to excessively wet spots that support anaerobic decomposition, the primary source of feedlot odor.
Sweeten also recommends applying water treatments during the early evening hours to coincide with the heaviest dust activity.
Changing the time of day cattle are fed and changing the fat content in cattle diets is also an option, according to the AgriLife article.
“Delaying the last feeding of the day until late afternoon may reduce animal activity during the critical dust-peak conditions near sunset.” An increase in the fat in cattle diets can result in a cohesive effect on manure, making it more resistant to being pulverized by hooves.
Controlling dust in alleys and on roads is also important. Regular watering of unpaved surfaces is helpful, as is applying resins or oil to dirt or gravel. Encouraging drivers to slow their speed also helps with road dust.