TWIN FALLS, Idaho – With 70 percent of Idaho’s 580,000 dairy cows located in the Magic Valley, managing manure and ammonia emissions are serious concerns for dairies, regulators and the public in southern Idaho.
In an effort to rein in ammonia emissions and odor from land applying liquid manure held in dairy lagoons, University of Idaho researchers are studying the effects of land application methods.
A number of dairies in the region use a flushing system to clean their facilities, resulting in a huge amount of lagoon water that is applied to cropland near the lagoons, said Lide Chen, a UI waste management engineer, presenting research findings at the 2014 Idaho Nutrient Management conference here.
When it comes to applying liquid manure, the issue is two-fold: the loss of valuable nitrogen due to the volatilization of ammonia and air quality. In addition, ammonia emissions give off odors annoying to nearby residents, he said.
The research compared current broadcast application of liquid manure to subsurface injection, which has been used successfully for some time to reduce ammonia emissions by 40 percent to over 90 percent in other parts of the country, he said.
The practice is still new to Idaho, however, and there have been no quantifications of emission reductions under Idaho conditions, he said.
The objectives of the research were to evaluate the method under Idaho conditions in terms of mitigating ammonia emissions and odor and estimate the associated costs, he said.
On-farm tests were conducted on a 3,500-cow dairy in southern Idaho. Liquid manure from one of the dairy’s lagoons was both surface broadcast and injected 8 inches into the ground in different areas at each of two sites. Air samples were collected, and invited trial participants evaluated odor on an olfactory basis.
Injecting the manure below the surface resulted in a 68 percent reduction in ammonia emissions and a 33 percent reduction in odor compared with surface broadcast, indicating subsurface injection can reduce ammonia emissions and odor in southern Idaho, Chen said.
In addition, ammonia emissions declined 35 percent in the second day of the surface broadcast trial. That suggests immediate incorporation of ammonia is required to reduce ammonia emissions, and the sooner the incorporation occurs the greater benefit in terms of reducing ammonia and nitrogen losses, he said.
Costs associated with the injection method were $15 to $30 per acre higher due to the need for a larger tractor and lower operating speed, and further studies are need to evaluate the cost and the agronomic benefits, he said.
Reduced ammonia emission and odor, nutrient retention of nitrogen for fertilizer, a reduction in environmental risks and fines, and better community relationships need to be considered, according to the researchers.
Other UI researchers involved in the project are: Wilson Gray, Howard Neibling, Sai Yadanaparthi, Mireille Chahine, and Mario de Haro Marti.