Effect of Phenylphosphorodiamidate on Ammonia Volatilization as Affected by Soil Temperature and Rates and Distribution of Urea1
- M-J. O'Connor and
- L. L. Hendrickson2
Laboratory incubation studies were conducted to evaluate the ability of phenylphosphorodiamidate (PPD) to inhibit urea hydrolysis and control NH3 volatilization losses. Complete hydrolysis of the uninhibited urea occurred within 8 d at all temperatures studied, and resulted in volatilization of more than 25% of the applied N within 10 d. Application of 20 mg PPD kg−1 of soil essentially prevented urea hydrolysis and resultant NH3 losses for 1, 2, 4, 8, and 17 d at 35, 25, 15, 10, and 5°C, respectively. This delay in the onset of NH3 losses due to PPD application kept NH3 losses during the first 10 d to <7% of the applied N at the three lower temperatures, but had little effect upon NH3 losses at 25 and 35°C. Such limited effectiveness of PPD at higher temperatures will no doubt reduce its utility for application to soils with surface temperatures above 25°C. Application of lower concentrations of urea gave reduced NH3 losses, both with and without PPD, likely due to a greater ability of other N transformations to compete for the reduced ammonium pools. Ammonia losses were also reduced, with and without PPD, when the urea was distributed throughout a larger soil volume, presumably due to a greater proportion of the urea being hydrolyzed below the immediate soil surface.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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