Kikuyu and annual pasture: a characterisation of a productive and sustainable beef production system on the South Coast of Western Australia

Abstract

Production parameters and water use of kikuyu (Pennisetum clandestinum) and annual-based pastures were monitored for a beef weaner production system from 1998 to 2000 in a paddock-scale demonstration on the south-east coast of Western Australia.

A paired paddock (40–105 ha) comparison was carried out between a kikuyu-based pasture (DSKikuyu) and temperate annual pasture (DSAnnual), with comparative measurements covering pasture production, composition and quality, and soil water deficits and drainage. The stocking rates for the paddocks were determined by the pasture productivity and cow P8 fat depth in the 'lactation phase' (April–December), and by sward management and soil stability imperatives in the 'dry cow phase' (January–March). Cow liveweight and P8 fat depth and calf liveweight were compared during the 'lactation phase'.

Kikuyu and annual pasture had similar carrying capacities through the 'lactation phase'. Kikuyu pasture carried more animals than annual pasture through the 'dry cow phase' (late summer and autumn) in all years. During late autumn, cattle were destocked from the annual pasture to reduce the risk of wind erosion and 'crash grazed' on the kikuyu pasture so as to reduce competition between kikuyu and regenerating annual grass and legume species.

The comparative quality and productivity of the kikuyu pasture in the lactation phase (winter and spring) was positively correlated with the level of winter legume present. When a similar level of winter legume was measured in the kikuyu pasture relative to the annual pasture (in 1998), the pasture quality, cow liveweight and condition and calf weaning weights were all comparable between the 2 pasture types. When a low legume component was recorded in the kikuyu pasture, the pasture quality and cow liveweight and condition were poorer than the annual pasture.

The kikuyu pasture growing on deep sandy soil developed a larger (mean 37 mm) soil water deficit than the annual pasture over the measurement period, and in particular from November to March. When integrated over a farm where kikuyu covers 40% of the total area, as was the case in this experiment, the resulting deep drainage was calculated to be just over half that of an equivalent whole farm of annual pasture.

Over the 3 years of monitoring, the combined system of annual and kikuyu pasture was calculated to have an annual gross margin 19% higher than the annual pasture alone. The major source of difference was no requirement for supplementary feed in the kikuyu–annual pasture system. This difference was limited however, by lighter post-weaning sale weights of cull cows from the kikuyu pasture in 'poor legume' years. There was no difference of calf weaning weights between treatments.

There is considerable opportunity to improve on this gross margin, through achieving a consistent strong presence of legume in the kikuyu pasture through winter and spring.