New Zealand Journal of Agricultural Research abstracts

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Agronomical and physiological responses of white clover (Trifolium repens) and perennial ryegrass (Lolium perenne) to nitrogen fertiliser applied in autumn and winter

M. L. Castle*
J. S. Rowarth^†
I. S. Cornforth^†

Soil, Plant and Ecological Sciences Division
P.O. Box 84
Lincoln University
Canterbury, New Zealand
email: maria.castle@agresearch.co.nz

*Present address: Plant Breeding and Genomics, AgResearch, Private Bag 3123, Hamilton, New Zealand.
† Present address: UNITEC, Private Bag 92 025, Auckland, New Zealand.

J. R. Sedcole

Applied Management and Computing Division
P.O. Box 84
Lincoln University
Canterbury, New Zealand

Abstract   Mixed pastures of white clover and ryegrass are profitable and widely used. However, loss of clover is common with time due to N fertiliser applications in late winter. The factors that cause this loss have yet to be determined. This work investigated reasons for the competitive disadvantage suffered by white clover relative to ryegrass in autumn and winter. White clover (Trifolium repens cv. ‘Grasslands Huia’) and ryegrass (Lolium perenne cv. ‘Grasslands Nui’) were sown in March in Canterbury, New Zealand, and grown as single plants in silica sand. Nitrogen (N; 0.5 mol m^-3 N); was applied daily simulating an unfertilised soil; solution N concentration was increased to 5.0 mol m^-3 N for treatments in autumn (May) or winter (August), simulating fertiliser treatment. Net photosynthesis was measured before each harvest and over a diurnal period at 123 days after sowing. Plants were destructively harvested six times (33-185 days after sowing) and plant dry weight and N concentration (%) measured. White clover had a significantly (P < 0.05) lower dry weight than ryegrass. Extra N applied from May significantly increased (P < 0.05) dry weight of ryegrass. No significant changes in shoot N concentration were found. Except at the last harvest, net photosynthesis was significantly lower (P < 0.05) in white clover than in ryegrass; this was also apparent for diurnal net photosynthetic rates 123 days after sowing. Results indicated that white clover growth was limited by temperature, whereas ryegrass growth was limited by N supply.

Keywords   apparent nitrogenase activity; Lolium perenne; nitrate; nitrogen fertiliser; perennial ryegrass; photosynthesis; Trifolium repens; white clover

A01030 Received 2 October 2001; accepted 21 August 2002; published 9 December 2002
New Zealand Journal of Agricultural Research, 2002, Vol. 45: 283-293
0028-8233/02/4504-0283 $7.00/0 © The Royal Society of New Zealand 2002

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