A dryland alfalfa (Medicago sativa) production system is being evaluated in the wheat-belt of Western Australia as an alternative to annual pasture leys. This is supported by the need to increase water-use to arrest rising water tables and associated land salinisation. Historically alfalfa has been restricted in WA due to acidic soils and the Mediterranean climate. However, the identification of more effective rhizobial inoculants (Evans and Howieson, 1992) and winter active cultivars has improved alfalfa productivity and persistence. Two experiments, (1) alfalfa versus sub-clover (trifolium subterranean) and (2) versus annual medic (Medicago polymorpha) were conducted on duplex soils, with pH's of 5.0 and 5.8 (CaCl₂). Comparative pasture growth rates and soil water assessments, with a neutron moisture meter, were measured. Average annual rain is 400 and 350mm (70% occurring April to October) with an annual pan evaporation of 1600 and 2000mm. Mean maximum temperature in summer 32^oC, minimum in winter 6^oC. Alfalfa plant densities were 30 and 50m^-2, the sub-clover >500m^-2 in both years, the annual medic 50m^-2 in first year, >300 in second year. Less than 100 plants/m^-2 of volunteer annual grass made up the remainder of the pasture. The alfalfa treatment maintained or increased bio-mass production (Table 1) and reduced water stored in the 0-150 cm soil profile (Table 2).

Eastern Australian studies have found that alfalfa will reduce stored soil water by extending the pasture growing season into the late spring and summer and may also increase pasture production (Crawford and Macfarlane, 1995). The results from this study suggest similar agronomic and environmental benefits may be achievable in Western Australia. The Australian Grains Research and Development Corporation provided financial support to this project.

Crawford, M.C and Macfarlane, M.R. 1995. Lucerne reduces soil moisture and increases livestock production in an area of high groundwater recharge potential. Aust .J. Exp. Agric., 35, 171-80.

Evans, P.M. and Howieson, J.G. 1992. More effective rhizobial inoculants improve the persistence of lucerne (Medicago sativa) in Western Australia. Proc. 6th. Aust. Agron. Conf., Armidale. p.552.