Arl. Cabezas et al., Calibration of a semi-open static collector for determination of ammonia volatilization from nitrogen fertilizers, COMM SOIL S, 30(3-4), 1999, pp. 389-406
Field quantification of ammonia (NH3) volatilization from applied nitrogen
(N) is limited because there are no simple inexpensive methods which measur
e losses without interference from the measuring equipment. Five greenhouse
experiments were conducted at the Center for Nuclear Energy in Agriculture
, Piracicaba, Brazil in order to estimate NH3 volatilization from applied N
using semi-open static collectors and the N-15 balance method. Urea, ammon
ium sulfate [(NH4)(2)SO4] and aqua ammonia labeled with N-15 were applied a
t rates from 5 to 100 mg N kg(-1) soil in pots containing 600 g of Oxisols
and Ultisols (0-20 cm). Efficiency of the equipment in capturing NH3 was de
termined by the ratio of volatilized NH3-N from the fertilizer labeled with
N-15 retained in the collector to the volatilized quantity obtained by the
N-15 balance method. Efficiencies varied from less than 1% to about 50% ba
sed on the mean rate of NH3-N from the fertilizer and the mean rate of tota
l NH3-N (fertilizer-N +soil-N) retained in the collector. The functions wer
e adjusted by correlating all collector efficiency values with the correspo
nding rates of fertilizer NH3-N and total N retained in the collector regar
dless of soil and climatic conditions or of fertilizer application method.
The models provided estimates of the efficiency of the collector for retain
ing NH3-N derived from fertilizer and the total NH3-N lost from the soil. T
he NH3-N losses were calculated based on the efficiency estimates. Losses f
rom fertilizers were not significantly different from losses determined by
the N-15 method when fertilizer N losses were greater than 0.11 mg day(-1).
Total loss estimates did not differ from the losses determined by N-15 bal
ance method for collector measured losses greater than 0.26 mg day(-1). The
se results showed that, if the quantity of NH3-N retained in the collector
and the efficiency of the equipment are known, the collector is a simple an
d inexpensive device for estimating actual NH3-N losses under varying soil,
climatic, and N fertilizer management conditions, without using expensive
N-15-fertilizer.