Nitrogen Content of Wheat and Corn in Response to the Application of Urea and the Urease Inhibitor N-(n-butyl thiophosphorictriamide)
Hefley, Chalone S
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Increasing nitrogen (N) uptake by crops is a primary goal of many crop producers due to the direct relationship between crop N content and higher yields. In order to increase N uptake by crops, the application of N fertilizer, specifically urea, is often used. However, N in the soil can be extremely volatile and is easily lost to the atmosphere through ammonia (NH3) volatilization before it is able to be used by the intended crops. Urease, an enzyme found in the soil, is a major facilitator of the NH3 volatilization process. Urease inhibitors were developed in order to delay the volatilization of N from N fertilizers, allowing more of the N to infiltrate the topsoil, thereby giving crops the opportunity to absorb the plant available N. This study was performed in an attempt to evaluate the effects of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on the harvested N content of wheat (Triticum aestivum L.) and corn (Zea mays L.) in the field. Six treatments, replicated four times each, were observed in completely randomized field plots each measuring 3.048 X 6.096 meters. The plots were treated with compost alone, compost treated with the NBPT-based inhibitor, N-YieldTM, urea alone, urea treated with N-YieldTM, urea treated with another NBPT-based inhibitor, Agrotain® (Ultra or Advanced, depending on the year), or were designated as a control group, wherein no fertilizer or urease inhibitor was applied. Once the crops reached maturity, they were harvested, and lab analyses were run on the dry matter harvested from each plot to determine nutrient values. In this study, N concentrations in wheat straw ranged from 0.64% in the control to 1.36% in the treatment containing urea treated with the NBPT-based inhibitor N-YieldTM, while N concentrations in wheat grain ranged from 2.09% in the control to 3.52% in the treatment containing urea treated with the NBPT-based inhibitor N-YieldTM. Similarly, N concentrations in the corn stover ranged from 0.81% in the compost treatment to 1.80% in the treatment containing urea treated with the NBPT-based inhibitor Agrotain®. However, the data analyzed in this study suggest that, in field conditions, while the application of urea fertilizer greatly increases N concentrations in wheat and corn, the addition of NBPT (whether Agrotain® or N-YieldTM) to urea before field application does not significantly increase N concentrations over that of urea alone.