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Time of planting affects seed production of burr medic

C.W. Thorn and G. Laslett

Western Australian Department of Agriculture, Marine Terrace, Geraldton WA 6530

Observations of Burr medic, Medicago polymorpha var. brevispina, suggested that seed production is decreased with increasing maturity. This trial examines the effect of time of planting (TOP) and maturity on time to flowering and seed production of burr medic.


The trial was conducted in 1987 at Kojonup, WA (450 mm May to October rainfall). Three burr medic lines from each of five maturity groups (early, early-mid, mid, mid-late, late) were sown at three planting times (30 April (T1), 3 June (T2), 6 July (T3)). Seed was sown at 10 kg/ha with P, S, Cu, Zn, Mo at 47, 55, 2.4, 1.2, 0.24 kg/ha respectively onto new land. Plots were hand sown and ungrazed. Days to flowering was recorded from seedling emergence to when 50% of plants had at least one open flower. Seed yields were measured using standard methods.

Results and discussion

Late maturing lines flowered up to 42 days earlier from July compared to the late April planting, while early maturing lines flowered only five days earlier under the same conditions. Flowering in burr medics is sensitive to the high temperature promotion effect once vemalisation is satisfied (1,2). This effect was less pronounced in the earlier maturity groups. Seed yields were decreased significantly by delayed planting (P<0.01) and by planting late maturing lines. Seed yields were reduced by between 6.9 and 10.1 kg/ha/day for each day seeding was delayed after 30 April. This trial highlights the importance of early sowing when re-establishing pastures.

Table 1. Effect of time of planting on burr medic seed production.


Clarkson, N.M. and Russell, J.S. 1975. Aust. J. Agric. Res. 26, 83-88. Hochman, Z. 1987. Aust. J. Agric. Res. 38, 0-8.

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