Control of vegetative and reproductive growth in sand burr (Cenchrus longispinus)

Abstract

Seeds and seedlings of the annual weed sand burr (Cenchrus longispinus) were introduced into undisturbed vegetation and fallowed soil in north-western Victoria. Survival and growth of the sand burr plants was significantly reduced on areas with a high density of skeleton weed (Chondrilla juncea), and on soils of heavy texture. The results suggest that sand burr will be confined to the margins of sand dunes and other places where the soil surface is sandy and relatively free of skeleton weed. Natural populations of sand burr produced sufficient dormant seeds in the stubble after cereal crops to enable the plant to persist through several years of ley pasture. Harbinger medic (Medicago littoralis) and lucerne (M. sativa) were sown under the cereal at two sites in 1971 to control sand burr seeding. Harbinger medic reduced sand burr density in the stubble at one site, but did not reduce seed production. Lucerne sown at 3.8 kg ha-1 or above reduced the number of dormant seeds formed in the stubble at the two sites. In the second year of pasture, the suppression of sand burr was independent of lucerne sowing rate.