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Fluid Journal : Fluid Journal 2002-2004
increases the likelihood that N will be available to crops when needed. Additionally, growers' investments are protected by ensuring crops receive the full benefit of N applications. Domestic studies Cool w eather. We know urease is abundant in most soil environments and its activity increases as soil temperatures increase. According to Dr. Mark Coyne of the University of Kentucky, urea hydrolytic rate will approximately double in soils between 50 and 86o F. However, urease activity can still be detected in frozen soils to -- 4oF and can abruptly change as periodic thaws raise temperatures above freezing in the first few inches of soil. Studies by Cargill Ag Horizon in Canada have shown that when UAN + NBPT was topdressed under such cool conditions (early spring), wheat yields increased 15 bu/A. Similar results have been reported by Miles Farm Supply in Centralia, Illinois, where UAN + NBPT increased wheat yields by 4.3 bu/A. Over-applying. Urease inhibitors have particular environmental value for growers who traditionally over--apply N to compensate for subsequent N losses. Properly used, urease inhibitors moderate N use by these growers. As explained by Dr. Wilbur Frye of the University of Kentucky, "Surface application, especially broadcast UAN, can result in substantial N losses through NH3 volatilization during hydrolysis of the urea, which is catalyzed by the urease enzyme." Corn trials. University of Illinois studies conducted by Dr. Bob Hoeft, have reported 15- to 20-bu/A increases when using NBPT with N applications. "Farmers should consider using Agrotain if tilling or if imminent rains are not going to push the N into the soil," Dr. Hoeft says. Bermudagrass. Researchers at the Noble Foundation in Ardmore, Oklahoma, have reported dry forage yield increases of 205 lbs/A when NBPT is added to N, even after significant rainfall four days after application. Cotton. At the University of Georgia, first-year research revealed that NBPT had the potential to increase sidedressed N efficiency, boosting lint yields 105 lbs/A more than untreated UAN---this despite receiving irrigation soon after sidedressing. Rice. A University of Arkansas study, evaluating several N fertilizer sources applied at several times 5 to 10 days prior to flooding, showed that adding NBPT to N significantly lowered ammonia volatilization losses. "The product," notes Dr. Rick Norman, "shows promise as a viable nitrogen source for delayed-flood rice when a farmer cannot get a flood across his field in less than three days." Canada Dr. Cynthia Grant of Agriculture Canada has worked extensively in demonstrating that urease inhibitors reduce ammonia toxicity when urea- containing fertilizers are placed near the seed. In studies at the Brandon Research Center, "Agrotain effectively reduced N volatilization in no-till where the N was not incorporated with tillage," said Dr. Grant. In recent wheat studies, the product reduced the risk of seedling damage when urea was placed next to the seed. Brazil Sugarcane. Urease inhibitors (Sao Pedro do Ivai in Parana) increased yield 7.1 tons/A, compared to N alone. Corn. L. A. Henkes of Sarandi, Rio Grade do Sul, reports that when urease inhibitor was combined with N in dry conditions, corn yields increased 8.3 bu/A. Other research in Mococa by Dr. Heitor Canterella, reports a 13.5 bu/A increase on no-till corn with the application of NBPT impregnated urea. The ability to inhibit urea and ammonium forms of nitrogen is the next frontier in achieving nitrogen efficiency. Allen Sutton is vice president of business and product development for Agrotain International, www.agrotain.com Early Spring 2003
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