A two-year study in Oklahoma (2010 and 2011) tested urea, Nutrisphere-N, Agrotain, and ESN in winter wheat.

Across both location and years there was no significant difference in wheat grain yield, protein, or residual soil nitrate levels when a product or additive was added and compared to urea at the same nitrogen rate. Regardless of tillage practice, there was no benefit in terms of yield or nitrogen concentration of using a slow release nitrogen source or a nitrogen stabilizer product.


Studies conducted in 2010 in Texas evaluated UAN, Nutrisphere-N, Agrotain Ultra, N-Sure, NDemand, and CoRon. Crops included corn, cotton, and grain sorghum.

For corn, there wereno differences in grain yield or test weight between the control and treatments receiving UAN, UAN with urease-nitrification inhibitors, or UAN blended with any of the three slow-release nitrogen products.  Likewise, there were no differences in cotton lint yield, gin turnout or fiber quality parameters between the control and any of the treatments, including various rates of nitrogen fertilizer using UAN, UAN with urease-nitrification inhibitors, or UAN blended with any one of three slow-release nitrogen products.  

Grain sorghum yield responded to increasing rates of coulter-banded UAN fertilizer applied at the second leaf stage. However, nitrogen stabilizers and slow release products surface dribble- banded at 30 and 60 pounds of nitrogen per acre did not improve grain sorghum yields compared to conventional UAN or urea at equal rates.

“Overall, this research indicates that crop response to the nitrogen stabilizer and slow release products evaluated was variable,” McFarland said. “While some of the products did show positive benefits, the results were not consistent across the different crops, sites, or years tested..”

He said environmental conditions in a given cropping season, particularly temperature and rainfall, along with soil type, are key factors in determining whether a nitrogen stabilizer or slow release product will protect nitrogen from loss and potentially improve crop response.

“Given the high cost of nitrogen and the environmental consequences of losses into surface water and groundwater resources, nitrogen fertilizers must be managed very carefully,” he added. “In the case of nitrogen stabilizers and slow release products, more research is needed to document precisely if, when, and where a specific product can help agricultural producers do that consistently and economically.”



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