Pasture legume production severely reduced when co-sown with winter forage cereals

Abstract

First year productivity of pasture legumes is lower than subsequent years due to low soil seed bank (in annual species such as medics) or because of slow early vigour (in perennial legumes such as lucerne and sulla). Establishing legumes into existing summer-growing grass pastures in autumn is difficult because of low soil moisture and the established grass competes strongly with emerging seedlings. This study examined the effects on establishment, early productivity and persistence of a range of sown pasture legumes when co-sown with winter-growing cereal forage crops. Five winter-sown legume species (snail medic, barrel medic, strand medic, sulla and lucerne) were sown alone and in combination with forage barley (Clifton, southern Qld) or oats (Warialda, northern NSW) at full (50 kg/ha) and half seeding rate (25 kg/ha). Competition from the forage cereals at both sowing rates reduced the growth of the pasture legumes by 80-98% in all species, but forage cereal production was not reduced by the legumes. Of the legumes sown alone, sulla was the most productive (>4.5 t DM/ha), but this was still about 50% of the forage cereal yield. While growers often establish pasture legumes under cereal grain crops sown at reduced densities, doing so with forage varieties sown at higher rates (>25 kg/ha) is liable to reduce seed set of annual species and establishment density of perennial species resulting in unviable pasture populations in subsequent years.