PLANT-POPULATION DYNAMICS IN SUBTERRANEAN CLOVER AND MUREX MEDIC SWARDS .3. EFFECT OF POD BURIAL, SUMMER GRAZING AND AUTUMN CULTIVATION ON EMERGENCE

Murex medic (Medicago murex Willd.) seedling recruitment is more sensi tive to soil water at the time of emergence than subterranean clover ( Trifolium subterraneum L.). Murex medic pods normally lay on the soil surface. Shallow burial of pods may be beneficial when soil moisture i s marginal for germination and emergence. In addition, the tightly coi led structure of murex medic pods may also act as a barrier to water u ptake by the seed. Two methods of burying murex medic pods were invest igated in the field: (i) trampling by sheep hooves through summer graz ing; and (ii) through light cultivation in autumn. A glasshouse experi ment was also conducted to examine the interaction between the length of time that the soil stays moist and pod burial for CD26 and CD53 mur ex medic and Dalkeith, Junee, Woogenellup subterranean clover. In the glasshouse, pod burial was important for the attainment of maximum eme rgence in all genotypes when soil water was limiting. However, pod str ucture did not appear to have a limiting role in germination and emerg ence in murex medic. When tested in the field, pod burial by sheep tra mpling through summer grazing improved emergence in CD26, possibly bec ause the smaller more open pod was more easily trampled than that of C D53. Summer grazing in CD53 and Dalkeith and autumn cultivation in all genotypes did not improve emergence; possible reasons for this are di scussed so to is the role of murex medic in ley farming systems in eas tern Australia.