Kikuyu and annual pasture: a characterisation of a ... - CSIRO Publishing

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temperate annual pasture (DSAnnual), with comparative measurements covering pasture ... for supplementary feed in the kikuyu–annual pasture system.
CSIRO PUBLISHING

Australian Journal of Experimental Agriculture, 2003, 43, 769–783

www.publish.csiro.au/journals/ajea

Kikuyu and annual pasture: a characterisation of a productive and sustainable beef production system on the South Coast of Western Australia M. M. McDowallA,C, D. J. M. HallA, D. A. JohnsonB, J. BowyerA and P. SpicerA AWA

Department of Agriculture, PMB 50, Esperance, WA 6450, Australia. BPO Box 363, Esperance, WA 6450, Australia. CAuthor for correspondence; e-mail: [email protected]

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. Introduction In southern Western Australia, secondary salinity is predicted to cover 30% of the agricultural landscape by 2070, assuming current land use management (Ferdowsian et al. 1996; State Salinity Council 2000). In Mediterranean climates, plant-based solutions to salinity depend on depleting stored water prior to the winter months, when rainfall invariably exceeds potential evapotranspiration resulting in excessive leakage beyond the root zone (Ridley et al. 1997). Summer-active perennial pastures have the potential to reduce soil water storage to the extent that they © CSIRO 2003

are seen as part of the solution to reducing secondary salinity (Cransberg and McFarlane 1994; Dunin et al. 1999; Hatton and Nulsen 1999). Despite the benefits of perennial pastures in land remediation, they occupy 40% of the agricultural land (State Salinity

10.1071/EA02230

0816-1089/03/070769

770

Australian Journal of Experimental Agriculture

Council 2000; George et al. 2001). Temperate perennial species have been trialed widely by producers on the south coast with limited success. Some of the factors contributing to poor uptake of temperate perennial species in this region are unreliable establishment, poor persistence, competition for land with cropping and no clear production benefit (J. Lemon pers. comm.). Kikuyu grass (Pennisetum clandestinum Hochst. ex Chiov) is a stoloniferous, rhizomatous, C4 perennial grass species, which is a native of the highlands of central East Africa. It was introduced to Western Australia in the 1920s and is now regarded as a useful pasture in the extreme south west of Western Australia (Lamp et al. 1990). It establishes readily from seed, spreads vigorously (Greathead et al. 1998) and is persistent. As a summer-active, perennial pasture, it potentially has some major environmental benefits compared to a temperate annual pasture, including increased plant water use over the summer, and greatly reduced risk of wind erosion due to the stoloniferous nature of the sward (Greathead et al. 1998). There is very little information available regarding the productivity parameters of kikuyu pasture in a