Persistence of annual and perennial legumes 12 years after sowing in the Monaro region of New South Wales

Productivity of introduced and native-based pastures across the Monaro region of NSW is often constrained by low legume content. Full pasture renovation is frequently precluded by landscape, soil or economic constraints with producers often spreading legume seed with fertiliser in an attempt to increase legume content in pastures. Four methods of legume introduction into an existing pastures (surface broadcasting and direct drilling with and without a pre-sowing glyphosate knockdown) at two landscape positions (north and south facing aspect) for four legume species, subterranean clover (Trifolium subterraneum), Caucasian clover (T. ambiguum), Talish clover (T. tumens) and lucerne (Medicago sativa) were investigated. Direct drilling after a glyphosate knockdown was the most successful method of introduction with subterranean clover achieving the highest seedling density. However, after 12 years, few legumes could be found on the north-facing aspect and subterranean clover had not survived on the south facing aspect. Legumes were found only in the direct drilled-glyphosate knockdown treatment; lucerne having the highest plant density and herbage availability. Where legume treatments had failed, populations of tall speargrass (Austrostipa scabra), a native perennial grass, had returned to their original density. A. scabra density was significantly lower on the south facing aspect in the lucerne and Caucasian clover treatments. There is capacity to introduce legumes into existing pastures but seed-soil contact and reduction in competition from existing pasture species at establishment is crucial to long-term persistence