Ammonia Volatilization from Nitrogen Fertilizer Surface Applied to Orchardgrass Sod
- J. W. Lightner ,
- D. B. Mengel and
- C. L. Rhykerd
If the N needs of the grass sward cannot be met with a compatible legume, then additional N inputs must come from other sources, such as urea, to sustain high yields. However, urea is difficult to incorporate in an established grass pasture, which can result in considerable inefficiencies in N utilization. One cause of this inefficiency is volatilization of NH3. Field measurements were made to determine the amount of NH3 lost through volatilization from urea-based fertilizers surface broadcast onto an orchardgrass (Dactylis glomerata L.) sod on a Xenia silt loam soil (a fine-silty, mixed, mesic Aquic Hapludalf). Nitrogen sources used were: urea applied as both a granular solid product and as a solution; cogranulated urea-urea phosphate (UUP); ammonium nitrate (AN); and urea-KCL and urea-CaCl2 solutions at a cation/urea-N equivalency of 0.50 KCl or 0.25 CaCl2·2H2O. Fertilizer N was applied at 200 kg N ha−1 in the spring and 100 kg N ha−1 in late summer. Measurable NH3 loss occurred within 12 to 24 h after N application. Rate of volatilization was greatest from mid-morning to early afternoon. Highest NH3 losses were from solid urea, urea solution, and urea-KCl solutions. Losses from these materials ranged from 27 to 41% of applied N in the spring and from 12 to 37% in the summer. No significant volatilization losses were observed with AN. Ammonia losses from UUP were significantly less than those from solid urea in the spring, and at least 40% less in the late summer. Relative to urea solution alone, mixing CaCl2 with urea lowered volatilization significantly in both 1983 studies. Finally, the concentration of KCl with urea in this study did not effectively reduce NH3 volatilization.
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