Plant population dynamics in subterranean clover and murex medic swards. 3. Effect of pod burial, summer grazing and autumn cultivation on emergence

Abstract

Murex medic (Medicago murex Willd.) seedling recruitment is more sensitive 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 is marginal for germination and emergence. In addition, the tightly coiled structure of murex medic pods may also act as a barrier to water uptake by the seed. Two methods of burying murex medic pods were investigated in the field: (i) trampling by sheep hooves through summer grazing; and (ii) through light cultivation in autumn. A glasshouse experiment was also conducted to examine the interaction between the length of time that the soil stays moist and pod burial for CD26 and CD53 murex medic and Dalkeith, Junee, Seaton Park and Woogenellup subterranean clover. In the glasshouse, pod burial was important for the attainment of maximum emergence in all genotypes when soil water was limiting. However, pod structure did not appear to have a limiting role in germination and emergence in murex medic. When tested in the field, pod burial by sheep trampling through summer grazing improved emergence in CD26, possibly because the smaller more open pod was more easily trampled than that of CD53. Summer grazing in CD53 and Dalkeith and autumn cultivation in all genotypes did not improve emergence; possible reasons for this are discussed so to is the role of murex medic in ley farming systems in eastern Australia.