Replacing a nitrophilous weed association with Phalaris aquatica and Medicago sativa on non-arable land

Abstract

In an experiment (1974 to 1978) carried out on the Central Tablelands of New South Wales, the effects of nine herbicide treatments, two intervals between spraying and sowing, and sowing in late autumn, on the ability of Medicago sativa, Phalaris aquatica and Vicia dasycarpa to establish, develop and replace a nitrophilous weed association (broadleafed plants, annual grasses and native perennial grasses) were measured. Herbicide treatment of the resident species was necessary for the establishment and development of M. sativa and P. aquatica but not for the establishment of V. dasycarpa. Successful treatments were: 2,2-DPA + amitrole, 2,2-DPA + 2,4-D, paraquat + diquat and glyphosate. Intervals of 7 and 28 days between spraying and sowing had no differential effect on establishment. Sowing in late autumn resulted in successful establishment of all species. Over four years the percentage ground cover of sown species on the herbicide treatments increased from 0% in early 1974 to 49% in late 1978; the control treatment rose from 0% to 12%. The percentage ground cover of the nitrophilous weed association on the herbicide treatments decreased from 76% in 1974 to 27% in 1978; the control fell from 76% to 68%. The experiment demonstrated that a nitrophilous weed association can be replaced with perennial pasture species on non-arable land on the Central Tablelands by using aerial techniques. Further research is needed to determine the optimum time of spraying and sowing.