Rh. Fox et al., ESTIMATING AMMONIA VOLATILIZATION LOSSES FROM UREA FERTILIZERS USING A SIMPLIFIED MICROMETEOROLOGICAL SAMPLER, Soil Science Society of America journal, 60(2), 1996, pp. 596-601
The large amount of unincorporated, urea-containing fertilizer that is
used on no-till corn (Zea mays L.) makes it imperative that we know t
he magnitude of NH3 volatilization loss from these fertilizers. Althou
gh there have been numerous studies to estimate these losses, in almos
t none of them were the losses measured under undisturbed field condit
ions. A simplified, micrometeorological method with NH3 samplers place
d at the center of three replicates of 25-m-radius circular plots was
used to estimate NH3 volatilization losses from 134 kg N ha(-1) of sur
face-applied, unincorporated urea, sprayed urea-ammonium nitrate (UAN)
solution, and dribbled UAN. The average NH3 volatilization losses dur
ing the first 10 to 20 d after application for a 3-yr period were 40,
22, and 17 kg N ha(-1) from urea, sprayed UAN, and dribbled UAN, respe
ctively. The losses from sprayed and dribbled UAN were not significant
ly different from each other and were, on average, significantly less
than from urea. The rainfall in the first 6 d after application was <5
mm for all 3 yr of the experiment. Corn yields and N uptake generally
reflected the measured NH3 volatilization losses, but were considered
to be much less precise indicators of NH3 volatilization loss. One dr
awback of the simplified micrometeorological method is that large area
s are needed to accommodate the 50-m-diam. plots and 100-m buffers bet
ween plots.