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Annual medic seed reserves in cereal rotations

R.A. Latta

Victorian Institute of Dryland Agriculture, Mallee Research Station, Walpeup VIC 3507

The productivity of annual medics in cereal pasture leys is largely determined by the amount of permeable seed available at the commencement of the pasture phase (1). Seed reserves of >200 kg/ha are required for satisfactory regeneration of medic pastures. This amount of seed in the soil results in >400 plants/m2 which is adequate for winter pasture production and weed suppression. Results of farm surveys in South Australia have shown that the seed reserves are often <200 kg/ha. The studies reported in this paper were undertaken to determine the effects of three cropping rotations on the seed reserves of Barrel medic (Medicago truncatula cv. Paraggio) when grown in an alkaline sandy loam at Walpeup.


In the first year Barrel medic was sown at Walpeup on 12 May 1987 at 8 kg/ha, in 40x3.5 m plots. Three rotations were imposed in years two and three; pasture-wheat (PW), wheat-pasture (WP) and fallow-wheat (FW). Experimental design was a randomised complete block with three replicates. Seed reserves were monitored annually by sampling to the depth of the cultivation layer (10 cm) in December. Seed was removed by hand and weighed. The plots were not grazed and weeds were controlled by selective herbicides. No seed was produced in either wheat or fallow phases.

Results and discussion

Table 1. Effect of crop rotation on medic seed reserves.

Seed production in the year of sowing (Year 1) exceeded 200 kg/ha. The soil reserve of medic seed following a WP or PW rotation was adequate for a regenerating medic pasture, however, following the FW rotation seed reserves were too low for satisfactory pasture regeneration.


Crawford, E.J. and Nankivell, B.J. 1989. Aust. J. Exp. Ag. 29, 183-188.

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