Identifying the causes of unreliable nitrogen fixation by strand medic (Medicago littoralis) based pastures

Fiona Tomney1, Brian Dzoma2, Ross Ballard3 and Nigel Wilhelm3

1SARDI, Minnipa Agricultural Centre, 226 McKenzie Rd, Minnipa SA 5654 fiona.tomney@sa.gov.au

2SARDI, Loxton Research Centre, Loxton SA 5333

3SARDI, Waite Research Precinct, Urrbrae SA 5064

Abstract

Following grower reports of low soil nitrogen (N) following vigorous medic-based pastures on the upper Eyre Peninsula of South Australia, management practices including herbicides and fertilisers were investigated for their effect on the N fixation of strand medic pastures at six field sites on the upper Eyre Peninsula. Applying phosphorus to soils with low P reserves at medic pasture establishment increased medic shoot dry matter and improved N fixation. The addition of urea at seeding reduced N fixation by the medics at some sites. Soil residues of the herbicide Logran reduced medic growth at one site. The application of a full label rate of Agritone 750 Herbicide (applied late when the medic plants were 5-7 cm in diameter) decreased pasture production and N fixation.

Host

The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography david_marland@hotmail.com Graham Centre for Agricultural Innovation, Charles Sturt University

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