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Santiago - an improved variety of burr medic

C.K. Revelll and M.A. Ewing2

1. Department of Agriculture, Dryland Research Institute, Merredin, W.A. 6415
2. School of Agriculture, University of Western Australia, Nedlands 6009

Spineless burr medic (M. polymorpha var brevispina) in conjunction with new acid tolerant strains of R. meliloti has proved to be well adapted to a range of mildly acid sandy loam soils in the drier wheatbelt of Western Australia. These soils have invariably had a history of poor legume content since traditional pasture species such as subterranean clover (T. subterraneum) and barrel medic (M. truncatula) have failed to persist. Until recently only two varieties were commercially available. These were Serena which flowers around 70 days after sowing and Circle Valley which flowers about 25 days after Serena. There was a strong need to develop varieties with a maturity intermediate between the two existing alternatives.


Preliminary screening work at a range of sites throughout the wheatbelt identified a group of lines with the desired maturity. These were seed increased and evaluated in large machine sown plots. Particular attention was placed on the performance of the pasture under various intensities of grazing. Specific measurements included winter and spring dry matter production, seed production and regeneration.

Results and discussion

A consistent feature of all the results is the superior seed production of the intermediate maturing group relative to Serena and Circle Valley, particularly when grazed extensively through the flowering period. The seed yield advantage is evident in both above and below average seasons.

Table 1. Effect of grazing intensity on the seed production (kg/ha) of selected medic varieties grown on a red-brown sandy loam at Merredin (Western Australia) in 1986.

Consideration of all the seed production and regeneration data resulted in the release of line N3146 registered under the name of Santiago. Its ability to maintain seed production under heavy grazing appears related to its capacity to develop sites of seed production close to the crown of the plant and to its maturity. It is able to make more use of late seasonal rains than Serena but unlike Circle Valley, does not totally rely on these rains to support the bulk of its seed production. The results highlight the need for testing new varieties with wide ranging maturities under some form of defoliation. The superior seed setting ability of Santiago under grazing is likely to give farmers more flexibility in grazing management during flowering than could be achieved with Serena and Circle Valley. This will be particularly important in below average seasons.

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