CSIRO, Division of Tropical Crops and Pastures, 306 Carmody Road, St. Lucia, Queensland, 4067, Australia.
Four treatments: (a) continuous grazing at 2.5 steers ha-1; (b) as (a) but with an initial lime application of 2 t ha-1; (c) as (a) but with the stocking rate doubled over summer to control grass growth; and (d) rotational grazing at 2.5 steers ha-1, were imposed on established pastures on two sites at Beerwah, in coastal subtropical Queensland from 1972 to 1978. This paper considers the effect of these treatments on the persistence of white clover in these pastures.
The frequency of white clover usually declined over summer and early autumn, but increased over winter to reach a peak in the following spring. This increase in the cooler months was due both to growth of surviving stolons and to regeneration from seed, but seedling regeneration was more important on the drier of the two sites. Soil seed reserves were greater (c. 6000 m-2 on the wetter site than on the drier site (c. 3000 m-2). Seedling densities in winter varied widely between years and sites, ranging from 1 to 700 m-2. Both seedling regeneration over winter and stolon survival over summer were usually greater on areas grazed more heavily during the previous summer, and on limed plots. Overall, the presence of white clover was more affected by site and climatic conditions than by management treatments. The factors determining persistence of white clover are discussed and the implications considered for commercial pastures, based on white clover, in subtropical Australia.