New Zealand Journal of Agricultural Research abstracts

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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

PDF file of entire paper: medium quality (614K); (scanned from paper original: notes about this process)

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