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Establishment of surface-sown pastures in wheat stubble in north western New South Wales

M.H. Campbell and A.M. Bowman

NSW Agriculture, Orange NSW 2800 Fox Street, Walgett NSW 2832

Pastures need to be established after a number of years of cropping in north-western NSW to repair soil structure and improve fertility. One method of establishment is to aerially sow seed into the stubble of a wheat crop.

Methods

Astrebla lappacea, Cenchrus ciliaris, Setaria incrassata, Panicum coloratum were surface sown (the first three in 1987 and all four in 1988, 1989, 1990) into wheat near Walgett just before and after harvest in randomised block experiments with four replications. Seed was treated with permethrin (0.13 kg a.i./100 kg) to reduce losses to harvester ants. Stubble was retained, reduced in height by cutting or removed. Establishment counts were made in summer or autumn following sowing and survival counts made over time (Table 1).

Results and discussion

Best establishment occurred in summer 1991 (Table 1) in response to 90 mm of rain in January and 25 mm in February. These plants produced large amounts of seed by April 1991 despite no rain in March or April and survived the following winter well. Grasses that established in autumns 1987 and 1988 had their numbers reduced by cold in the following winter but produced sufficient seed to enable recruitment in autumn 1990 (Table 1). The 1987 and 1988 sowings survived heavy and lax grazing respectively; the ground cover of A. lappacea, P. coloratum, S. incrassata and C. ciliaris in the 1988 sowing being, respectively, 46,40, 39 and 2% in January 1991. Low ground cover of C. ciliaris was due to cold damage and drift from glyphosate applied to an adjoining crop.

Table 1. Establishment and survival of perennial grasses (meaned for three species in 1987 and four species in 1988-90) surface-sown into wheat crops just before or after harvesting.

Stubble treatments and sowing before or after harvest had little effect on establishment or survival. Percentage establishment of C. ciliaris was highest and that of P. coloratum lowest with the reverse true for cold tolerance. P. coloratum was the most persistent grass up to 1991. The major advantage of sowing after cropping is that weeds are virtually eliminated.

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