Urease Inhibition in Solutions and Urine

Abstract. Urea has the highest fraction of nitrogen among common fertilizer materials. Swine urine has potential as a source of urea if the urine can be collected before urea is hydrolyzed to ammonia and carbon dioxide by urease enzymes which are abundant in . The ammonia then volatilizes to the atmosphere or oxidizes to nitrite and nitrate and may move into groundwater. Thus urea hydrolysis in manure can be a major source of nitrogen pollution of the environment and loss of a valuable plant nutrient. This study consists of four lab experiments to test the effectiveness of urease inhibition on fresh swine urine by adjusting pH. A jack bean urease enzyme preparation was added to solutions of reagent-grade urea and to urine collected directly from gestating sows. Sulfuric acid and sodium hydroxide were added to the solutions to either lower or raise the pH and allowed to incubate at room temperature. Additionally NBPT, a common soil urease inhibitor was also tested for effectiveness in preserving urea in both urea solution and urine. The release of ammonia and preservation of organic nitrogen from these solutions were quantified periodically over several weeks. Results indicate that a solution pH below 3 or above 12 is most effective at inhibiting urease activity while NBPT also demonstrated some effectiveness at preventing urea hydrolysis in solution.