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Establishment of surface-sown pastures on cracking clays near Walgett

M.H. Campbell1 and W.D. Bellotti2

1 Agricultural Research and Veterinary Centre, Forest Road, Orange
N.S.W. Department of Agriculture, Walgett, 2832

More than 45% of land in western N.S.W. requires treatment to restore degraded vegetation or to control erosion (1). Research into the applicability of surface sowing as a method of establishing exotic and native pasture species in this area could result in large areas being sown quickly and cheaply by using aerial techniques (2). Investigations were started near Walgett on grey cracking clays because previous research, near Coolah (3), had shown that surface sowing could be successful on similar soils.


Seeds of six pasture species (Afedicago truncatula, cv. Sephi; AL sativa, cv. Baron; Phalaris aquatica, cv. Sirolan; Astrebla lappacea; Setaria incrassata, cv. Inverell; and Panicum coloratura, var. makarikariense cv. Bambatsi were surface sown on a fenced area on June 18, before the seasonal break, and on August 18, 1986, after the seasonal break. Broadleafed weeds (mainly Brassicaceae) were sprayed with glyphosate immediately before sowing (2 treatments) and with 2,4-DB after sowing (1 treatment, Table 1). All seeds (spikelets of A. lappacea) were treated with permethrin to reduce losses from seed-harvesting ants; no fertilizer was applied. Rainfall was: June 0, July 85, Aug. 29, Sept. 95, Oct. 41mm. Establishment (number of plants / 4 x 0.25m2 quadrats / plot) and botanical composition (% ground cover, visual estimate) were recorded in October 1986.

Results and Discussion

In the nil herbicide treatments establishment of M. sativa and P. aquatica was higher (P<0.05) from the June sowing because sown species germinated with the weeds whereas the weeds were already present and competitive at the August sowing (Table 1). Time of sowing had no effect on establishment in the plus herbicide treatments because AL sativa and P. aquatica germinated with the weeds in both sowings while A. lappacea, S. incrassata and P. coloratura germinated in September (delayed by low temperatures) after the weeds. Plants of M. sativa and P. aquatica were much larger on the June sowings but plants of A. lappacea, S. incrassata and P. coloratura were largest on treatments sprayed in August. Although the establishment of AL truncatula was not influenced by treatment its growth was much greater from the June sowings.

Table 1. Establishment (% viable seed) of sown species and ground cover (%) of weeds on October 23, 1986

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