The effects of native grass cover, species, herbicide and sowing method on legume establishment on the northern slopes of New South Wales

Abstract

The effects of sowing method (direct drilling or broadcasting), level of cover of native grass and pre-sowing herbicide application on pasture legume introduction were evaluated from 1984 to 1987 at a low elevation (425 m) site on the Northern Slopes of New South Wales. Two perennial (Medicago sativa cv. CUF101 and Onobrychis viciijolia cv. Eski) and 3 annual legumes (Trifolium subterraneum ssp. brachycalycinum cv. Clare; M. truncatula cv. Sephi; Vicia villosa ssp. dasycarpa cv. Namoi) were sown each year from 1984 to 1986. Seedling establishment was measured 3-4 months after sowing, and where possible, the dry matter yields of the sown legume were also estimated. Seedling regeneration was measured in 1987 and the yield of legumes sown in 1985 was determined in 1986. All species failed to establish under the dry conditions experienced in 1984. In subsequent years seedling numbers of the annuals were higher than those of the perennials. Direct drilling increased establishment of all species compared with broadcasting. The provision of a large amount of cover by the resident native grasses (4.6-7 t/ha of dry matter, 0.6-0.7 In in height) also substantially increased seedling establishment in cvv. Clare, Sephi and CUFlO1. None of the treatments used were successful in establishing cv. Eski. Herbicide application prior to sowing did not significantly affect seedling numbers in the establishment year but resulted in higher numbers of seedlings regenerating in subsequent years, particularly in cv. Sephi. Seedling regeneration of the annuals was also increased (P<0.05) by direct drilling into moderate or high levels of vegetative cover. Dry matter yields of all sown species except cv. Namoi were low, and the environment was difficult for legume survival and production. This was attributed mainly to the variable rainfall that occurs at this low elevation, while for lucerne high summer temperatures probably affected its performance.