Author
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Varel, Vincent |
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Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/27/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Laboratory experiments were used to evaluate the feasibility of using various chemicals to control ammonia nitrogen volalitization from feedlot pens. It is estimated that 75% of the nitrogen excreted by cattle is lost to the atmosphere; most being lost by the rapid conversion of urinary nitrogen (urea) to ammonia, by microorganisms which produce the enzyme, urease. This nitrogen loss contributes to odor, environmental consequences, and loss of a valuable fertilizer resource. This work demonstrates that inhibitors of urease used in the fertilizer industry for slow-release of urea fertilizers, may have applications in controlling urea loss in feedlot wastes. The most effective control in preventing urea degradation was obtained by adding the inhibitors each week. This treatment conserved 70% of the urea nitrogen in cattle waste after 28 days. While weekly additions of urease inhibitors may not be practical in the feedlot, encapsulation of the inhibitors or similar techniques may provide a slow release effect and give a longer term inhibition of urease; thus, eliminating weekly additions. This technology may give added value to livestock wastes, which are now being disposed of by least-cost procedures. Technical Abstract: Current waste management systems for cattle feedlots and swine facilities result in nitrogen losses of approximately 75%. Most of this loss occurs through the rapid hydrolysis of urinary nitrogen (urea) to ammonia, which volatilizes into the atmosphere. This contributes to odor, environmental problems, and loss of a valuable fertilizer resource. Urease inhibitors cyclohexylphosphoric triamide (CHPT) and phenyl phosphorodiamidate (PPDA) were used to control the hydrolysis of urea in duplicate one-liter slurries of cattle and swine wastes. With cattle waste and swine waste, both inhibitors at 10 mg/l of waste prevented hydrolysis of the urea for 4 to 11 days, and then a gradual hydrolysis occurred until complete at day 28. Hydrolysis of urea in untreated cattle or swine waste (controls) was complete within one day. The most effective control in preventing urea hydrolysis was obtained by adding the inhibitors each week. Weekly add- itions of 10, 40 or 100 mg PPDA per liter of cattle waste prevented 38, 48 and 70% of the urea from being hydrolyzed after 28 days, respectively. With swine waste these PPDA concentrations prevented 72, 92 and 92% of the urea from being hydrolyzed after 28 days, respectively. PPDA additions were stopped after 49 days, and all urea at the three PPDA concentrations was hydrolyzed after 70 and 84 days for the cattle and swine wastes, respectively. These results offer a strategy for significant control of ammonia emissions from livestock facilities and increasing the fertilizer value of wastes by improving the nitrogen to phosphorous ratio for plant growth. |
