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Effect of burial on longevity of seeds of medicago polymorpha andtrifolium subterraneum

H.M. Saoub, C.K. Reve11, G.B. Taylor and W.R. Stern

University of Western Australia, Crop and Pasture Sciences, Nedlands WA 6009
CSIRO, Division of Animal Production, Wembley WA 6014
Western Australian Department of Agriculture, Dryland Research Institute, Merredin WA 6415

The effect of a cultivate/seed tillage system on the burial and subsequent rate of loss of residual pasture seeds was investigated during 1989-90 at a low rainfall wheatbelt site in Western Australia.


In May 1988, Trifolium subterraneum cv. Dalkeith and Medicago polymorpha cv. Santiago were sown at Merredin, 260 km east of Perth. In the following year, wheat was sown on 1 June 1989 through a combine seeder after a single pass with a scarifier on 28 April 1989. At various times over the next 18 months soil samples were collected from cores (0.01 m2) taken at depth intervals of 0-3, 3-6 and 6-9 cm. Seeds were recoverd from the cores, counted and tested for permeability.

Results and discussion

The distribution of seeds in the cultivation layer immediately after seeding was 84%, 14% and 2% for Dalkeith and 70%, 25% and 5% for Santiago in the 0-3, 3-6 and 6-9 cm depth intervals, respectively. Similar effects of tillage on seed burial have been found previously (1). Seed numbers of Dalkeith declined more rapidly at all soil depths compared with those of Santiago (Fig. 1). However, burial had a more marked effect in reducing the rate of loss of Dalkeith seeds. We attribute this burial effect to different rates of seed softening caused by the different temperature conditions experienced by the seeds. Similar effects of burial have been reported for other cultivars of T. subterraneum and M. polymorpha (2). The results indicate that while tillage should lead to the build-up of a longer soil reserve of Dalkeith seeds in ley-farming systems, it will have little direct impact on reserves of Santiago seeds.

Figure 1. Effect of depth of burial on decline in seed population with time.


Taylor, G.B. 1985 Aust. J. Exp. Agric. 25, 568-573.

Taylor, G.B. and Ewing, M.A. 1988. Aust. J. Exp. Agric. 28, 77-81.

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