New Zealand Journal of Agricultural Research abstracts
Nitrate leaching from dairy shed effluent and ammonium fertiliser applied to a
free-draining pasture soil under spray or flood irrigation
H. J. DI
K. C. CAMERON
S. MOORE
N. P. SMITH
Soil, Plant and Ecological Sciences Division
P. O. Box 84
Lincoln University
Canterbury, New Zealand
Abstract The potential for contamination of groundwater by
dairy shed effluent (DSE) and ammonium N fertiliser (NH4Cl) was assessed by
measuring nitrate leaching from 16 large soil lysimeters (80 cm diam. x 120 cm
depth). Each lysimeter contained an undisturbed monolith of Templeton fine
sandy loam (Udic Ustochrept) located in Canterbury, New Zealand, with
established perennial ryegrass (
Lolium perenne) and white clover
(
Trifolium repens) pasture plants. DSE and NH4Cl were applied at 400 kg
N ha
-1 yr
-1, in two split applications of 200 kg N
ha
-1. During the summer, each lysimeter received either spray (50 mm
mo
-1) or flood (100 mm mo
-1) irrigation. During the
winter, the natural rainfall received was supplemented with simulated rainfall
in order to reach the 75th percentile of local rainfall records for the winter
period.
The concentration of nitrate in the leachate reached 5 mg N l-1
under both flood and spray irrigation following the first N fertiliser
application (Dec 1995), but did not increase above control values (<1 mg N
l-1) following the first DSE application. After the second
DSE/fertiliser application (May 1996), the nitrate concentration in the
leachate increased significantly during the winter/spring period, and appeared
to be influenced by the antecedent summer irrigation conditions. Under spray
irrigation, the nitrate concentration peaked at 40 and 17 mg N l-1
for the N fertiliser and DSE, respectively. Under flood irrigation, nitrate
reached 25 and 10 mg N l-1 for the N fertiliser and DSE,
respectively. The lower nitrate concentrations in the leachate under flood
irrigation were attributed to the greater loss of nitrogen by denitrification
and the greater dilution of soil solution nitrate by the larger volume of
irrigation water applied. Enhanced denitrification from the higher moisture
content in the flood/DSE treatment resulted in a smaller N leaching loss
compared with the spray/DSE treatment. The amount of total mineral N (nitrate,
ammonium, and nitrite) leached was smaller from the DSE than from the N
fertiliser.
Keywords Soil; environment; organic waste; N fertiliser;
nitrate leaching; grassland; denitrification
New Zealand Journal of Agricultural Research, 1998, Vol. 41: 263-270
0028-8233/98/4102-0263 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (639K); (scanned from paper original: notes about this process)
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