Abstract
Animal agriculture is a significant source of atmospheric ammonia. Ammonia (NH3) volatilization represents a loss of plant available N to the farmer and a potential contributor to eutrophication in low-nitrogen input ecosystems. This research evaluated on-farm slurry treatments of alum or zeolite and compared three diets for lactating dairy cows in their effectiveness to reduce NH3 emissions. NH3 emissions were compared using a group of mobile wind tunnels. The addition of 2.5% alum or 6.25% zeolite to barn-stored dairy slurry reduced NH3 volatilization by 60% and 55%, respectively, compared to untreated slurry. The alum conserved NH3 by acidifying the slurry to below pH 5, while the zeolite conserved ammonia by lowering the solution-phase nitrogen through cation exchange. The use of alum or zeolite also reduced soluble phosphorus in the slurry. NH3 loss from fresh manure collected from lactating dairy cows was not affected by three diets containing the same level of crude protein but differing in forage source (orchardgrass silage vs. alfalfa silage) or neutral detergent fiber (NDF) content (30% vs. 35% NDF). NH3 losses from the freshly excreted manures occurred very rapidly and included the urea component plus some unidentified labile organic nitrogen sources. NH3 conservation strategies for fresh manures will have to be active within the first few hours after excretion in order to be most effective. The use of alum or zeolites as an on-farm amendment to dairy slurry offers the potential for significantly reducing NH3 emissions.
Highlights
Ammonia (NH3) volatilization from farm manure is a major source of N loss to the environment
NH3 losses from either 2.5% alum or 6.25% zeolite were negligible after 12 h, and total losses amounted to about 5% of the slurry total Kjeldahl N (TKN) with alum and about 7% of the TKN for zeolite (Fig 1)
Others have shown zeolite to have excellent NH3-absorbent properties[26]. These results demonstrate that acidification with alum and sequestering NH4-N on zeolite exchange sites are both effective methods to reduce NH3 losses from dairy slurry
Summary
Ammonia (NH3) volatilization from farm manure is a major source of N loss to the environment. The lost NH3 affects farm economics by causing farmers to purchase N fertilizers for crops, and contributes to eutrophication in low-N input ecosystems through atmospheric transport and deposition[1,2]. Agriculture is the major source of NH3 emissions to the atmosphere, contributing an estimated 90% of total NH3 emissions in the U.S.[4] and in Western Europe[5,6,7]. Most efforts to reduce NH3, which have highlighted the benefits of immediate soil incorporation[11,12], have focused on land application[7,10,11,12]. This paper will report NH3 loss studies focusing on farm-level manure treatment and on animal diet
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