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Loss of surface-sown perennial grasses in their establishment year in north-western New South Wales

M.H. Campbell1 , W.D. Bellotti2 and C.R. Watson3

1Agricultural Research and Veterinary Centre, Orange, NSW 2800
2
Turretfield Research Centre, Rosedale, SA 5350
3
NSW Agriculture and Fisheries, Walgett, NSW 2385

Much of western New South Wales requires the re-establishment of perennial grass pastures to increase production, control weeds, build soil fertility or minimize erosion. Surface sowing offers a quick and cheap method of establishing native or exotic perennial grasses and annual legumes. Investigations in 1988 on grey cracking clays were aimed at assessing the applicability of surface sowing as a method of establishing perennial grasses in the Walgett environment.

Methods

Seeds of four perennial grasses (Panicum coloratum var. Makarikariense cv. Bambatsi; Setaria incrassata cv. Inverell; Astrebla lappacea; Cenchrus ciliaris cv. Biloela) were surface-sown on a fenced area on February 3, 1988. All seeds were treated with permethrin to reduce losses from seed-harvesting ants; no fertilizer was applied but a selective herbicide (metsulfuron) was applied in late July to control broadleaved weeds (mainly Brassicaceae, winter and spring growers) that established with the sown species in April. Plant numbers were counted in May and December 1988. Climatic data follows: monthly rainfall from January to December 20, 66, 6, 190, 43, 31, 70, 42, 31, 4, 34, 57 mm; mean monthly screen temperatures for June, July and August 5.8, 6.5, 6.2C; and number of 2C frosts for June, July and August 1, 3, 4.

Results and discussion

Good rain in April and May promoted establishment and growth of all species. By early winter grass plants had from 6 to 40 leaves and were from 6 to 20 cm high. Despite a relatively mild winter (mean min. 6.2C compared to the long term mean of 5.2C) all species were severely damaged by light frosts. In late August, most small plants were completely brown and larger plants almost completely brown; P. coloratum had more green tissue than other species. By December plant numbers had declined on all treatments, the greatest decline occurring with C. ciliaris (+ and -herbicide) and A. lappacea (- herbicide, Table 1). We apportion most of the losses to low temperature damage in winter (C. ciliaris), competition for light and moisture in spring (A. lappacea) or the interaction of low temperature damage and competition (P. coloratum, S. incrassata). The results demonstrate the need to control competition and to procure perennial grasses that are more tolerant to cold during establihsment than the species sown in experiments at present on the north-western plains of New South Wales.

Table 1. Decline in plant numbers between May and December 1988

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