ISSN:
1573-0867
Keywords:
NH3 volatilization
;
NH3 losses
;
urea-N losses
;
urea efficiency
;
N efficiency
;
calcareous soil
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Severe losses of NH3 by volatilization are often reported when urea is surface applied to calcareous soils. Applications on wet soils may increase these losses. This study with N rates of 0, 20, 40, 80, 160, and 320 kg ha−1 estimates the efficiency of urea application and predicts NH3-volatilization losses when urea is surface applied on a wet calcareous soil. Placements consisted of three different methods of applying urea on or in the dry soil just prior to irrigation and a surface-broadcast treatment following irrigation. There were no significant yield differences between dry-soil placements, but all dry-soil placements gave significantly higher yields than did broadcast placement of urea on the wet soil. Thus, a second-order regression equation relating N rate and yield for dry-soil placements and another for wet-soil placement were used to determine the efficiency of wet- vs dry-soil applications of urea and to predict NH3-volatilization losses from the wet soil. The efficiency was determined by three different procedures. The first compared the amount of N needed for wet- vs dry-soil conditions to produce discrete yields. The second compared the slope of the yield curves at discrete yield levels to determine the ratio of the amount of N needed to produce one additional increment of yield under wet- vs dry-soil conditions. The third was an estimation of the availability coefficient according to a method recently developed by HR Tejeda and others. Predicted NH3 -volatilization losses were calculated from the efficiency values because loss of NH3 from urea applied on or in dry soil followed very shortly by an irrigation should be almost nil. The efficiency factors averaged 55% for the first procedure and 51% for the second while the availability coefficient was 59%. Thus, the average estimate for efficiency of urea on wet vs dry soil was 55% and predicted losses of N by NH3 volatilization averaged 45% when urea was applied to the wet surface of this calcareous soil.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01049483
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