New Zealand Journal of Agricultural Research abstracts
Nitrate leaching from ploughed pasture and the effectiveness of winter catch
crops in reducing leaching losses
R. D. McLENAGHEN
K. C. CAMERON
Department of Soil Science
P.O. Box 84, Lincoln University
Canterbury, New Zealand
N. H. LAMPKIN
Welsh Institute of Rural Studies
University of Wales
Aberystwyth, Dyfed, United Kingdom
M. L. DALY
AgResearch
Canterbury Agriculture and Science Centre
P.O. Box 60
Lincoln, New Zealand
B. DEO
Crop and Food Research
Private Bag 4704,
Christchuch, New Zealand
Abstract The effect of five catch crops (ryecorn, ryegrass,
mustard, lupin, bean) on nitrogen (N) leaching following the autumn ploughing
of a grass ley was compared with N leaching from bare fallow soil. The
concentrations of nitrate N and ammonium N in the drainage water and the
quantities of drainage water from the various treatments were measured over a
winter period using undisturbed soil monolith lysimeters. Nitrate was the
dominant form of N leached. The amount of N leached from soils with the
ryegrass catch crop (2.5 kg N/ha) was considerably less than that leached from
fallow soil (33 kg N/ha). Nitrate concentrations in the drainage water from
soils growing ryecorn and ryegrass were less than 10 mg N/litre, whereas that
from lysimeters growing lupins or beans and from the fallow soil exceeded this
value. Shoot dry matter yield for mustard (5.91 t/ha) and ryecorn (5.25 t/ha)
was at least twice that of the other crops and very much higher than the 0.49
t/ha produced by the weeds in the fallow treatment. Nitrogen concentrations in
the shoots ranged from 1.9 to 3.3% for the mustard and control plots
respectively with the other crops averaging 2.2-2.6%. Total plant uptake of N
by ryecorn (170 kg N/ha) was significantly higher than that by ryegrass, bean,
and lupin (111, 96, and 99 kg N/ha respectively) and very much higher than the
39 kg N/ha taken up by weeds in the fallow plot.
Keywords soil; nitrate; nitrogen; leaching; catch crops;
environment; lysimeter; ploughing; pasture
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 413-420
0028-8233/96/3903-0413 $2.50/0 (c) The Royal Society of New Zealand
1996
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