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The growth and development of exotic medicago spy. at Roseworthy, south Australia

R.S. St John-Sweeting, A.A. Mohamed and G.C. Auricht

Department of Agricultural Technology. The University of Adelaide, Roseworthy SA 5371 South Australian Department of Primary Industries

Annual species of the genus Medicago are an integral component of many pastures in the South Australian dryland farming systems. This project investigated the potential of Medicago spp. not normally grown in South Australia, to ascertain if any had winter or spring dry matter production significantly greater than the commonly grown barrel medic. M.truncatula cultivar Paraggio.


Single accessions of 12 Medicago species were selected from the Australian Medicago Genetic Resource Centre Collection on the basis of flowering date and herbage production and compared to M.truncatula, cv. Paraggio (Table I). The experiment was conducted at The University of Adelaide's Roseworthy Campus, 50 km north of Adelaide. The soils are alkaline solonised brown loams (malice). The average annual rainfall is 440 mm predominantly of winter incidence. The field trial consisted of a randomised block design with six replicates. Seedlings were established in peat jiffy pellets on 15 May. All lines were inoculated with a mix of Rhizobium meliloti cultures at the time germinated seeds were being transplanted into peat pellets. 25 medic seedlings of each line were hand planted on 12 June at 0.15 m intervals within 3.8 m long rows. Rows were spaced 1.5 m apart. Dry matter production was measured as total shoot weight of five plants from each row, one set of five to assess winter growth to 27 August, and another set for growth to 20 October.

Results and discussion

Table 1. Mean dry matter production of medic plants over winter and over the winter-spring period.
Pairs of means with no common letters following are significantly different (P = 0.05).

M.arabica produced 78.5% more and M.turbinata 26% more dry matter than M.truncatula cv. Paraggio up to 20 October. These two species were as productive as Paraggio up to 27 August. Whilst all lines were inoculated with Rhizobium, the poor performance of M.rigidula contrasts with earlier results from Parafield and is most likely to be attributed to a lack of adaptation to light textured soils and to poor nodulation resulting from the absence of a suitable Rhizobium strain.

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