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The effects of cereal straw on productivity of annual medic pastures

P.E. Quigley and E.D. Carter

Agronomy Department, Waite Agricultural Research Institute, The Dniversity of Adelaide, Glen 0smond, South Australia 5064.

It is a common observation that high concentrations of cereal straw, especially that left in walker rows after grain harvest, inhibit the development of medic-based pasture in the wheat-sheep zone of South Australia and elsewhere. Studies on the effects of cereal residues on the germination and early development of other crop species have been undertaken (1, 2) but the effects of straw on regenerating annual pastures has received little attention. This paper reports a preliminary survey aimed at quantifying the effects of straw in field situations.


Six stubble paddocks, located on Yorke Peninsula, South Australia, were sampled in mid-spring 1983. Botanical composition, percentage bare ground and medic plant density were assessed in quadrats located on straw walker rows and on adjacent inter-row areas. Vegetation was cut to ground level and samples handsorted into straw, medic, green cereal and weed components and oven dried. The width of walker rows and spacing were measured.

Results and Discussion

At all sites medic density was significantly reduced in straw walker rows and there were concomitant reductions in medic herbage production (Table 1).

Table 1. Effect of straw walker rows on medic plant density and dry matter yield of pasture sward components.

At sites 4, 5 and 6, where there were large ranges in medic herbage production, regression analysis was used to demonstrate an exponential decline in medic dry matter as straw density increased, r2=0.89, 0.77. 0.71 respectively. The percentage bare ground was always greater on the walker rows compared with between rows. Taking into consideration the width and spacing of the walker rows and the retardation of medic herbage in the rows it was found that walker rows reduced medic dry matter, over an entire paddock, by 15.3% (mean of five sites).

1. Kimber, R.W.L. 1967. Aust. J. Agric. Res. 18 : 361-374.

2. Lovett, J.V. and Jessop, R.S. 1982. Aust. J. Agric. Res. 33 : 909-916.

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