In Queensland, lucerne (Medicago sativa) is grown both as a cash crop for hay production and as a pasture plant. In 1998-99 there were over 25 000 ha of pure lucerne grown under irrigation, producing about 185 000 t of hay worth $40 million. Considerably larger areas are also being sown without irrigation in pure and mixed stands for cattle and sheep production, making it one of the most valuable pasture plants in the State. In extensive dryland grain-growing areas of northern New South Wales and southern Queensland, lucerne is sown in rotations with grain crops to help improve grain yield and quality. Problems in grain yield and quality are associated with a long history of continuous cropping that has led to soil fertility decline. Areas of both dryland and irrigated lucerne are expanding in Queensland.
Lucerne is grown best between latitudes 24°S to 29°S and longitudes 148°E to 153°E, in areas with 550 to 900 mm annual average rainfall. The climate of this area is subtropical, ranging between warm to hot and humid in summer, and mild to cool and dry in winter. Light frosts occur between May and September. Lucerne is generally grown for hay in the more humid areas on deep alluvial soils ranging from sandy clay-foams to heavy clays. For grazing, it is grown in all climates within the zone on deep uniform clays, red earths and a variety of duplex soils. A large proportion of the lucerne grown for hay is produced under irrigation.
Lucerne is a strongly taprooted perennial grazing and fodder legume. When used for hay or grazing, the management of lucerne rarely allows it to set seed. Therefore, productive lucerne stands must be well established and well managed to persist, as stands rarely thicken through the recruitment of seedlings. Thus, understanding lucerne and its problems is the key to gaining the most from lucerne.
Until the late 1970s, lucerne cultivar improvement was restricted by limited access to germplasm from overseas. With the advent of lucerne aphids in 1977, those restrictions were lifted. This led to a number of lucerne breeding programs and, after more than 20 years, there are now many good cultivars with widely differing characteristics available to growers. Apart from varying disease and insect resistances, many of these cultivars have growth patterns different from that of the old, superseded winter semi-dormant cultivar Hunter River, and consequently quite a different potential growth in each season, particularly in winter.
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History
Lucerne is thought to have originated somewhere in north-western Iran and north-eastern Turkey. Lucerne, as we know it, is part of the Medicago sativa complex, which includes M. sativa ssp. sativa (the purpleflowered or common type), M. sativa ssp. falcata (a yellow-flowered type) and M. sativa ssp. glutinosa. Almost all the cultivated lucernes in the world are based on M. sativa and we refer to this species when we use the term ‘lucerne. However, many of the cultivars worldwide do contain a proportion of M. sativa ssp. falcata genes.
The three sub-species are cross-pollinated and can freely interbreed, giving a range of types with varying characteristics. The yellow-flowered M. sativa ssp. falcata type has contributed winter hardiness, drought resistance and the ability to develop creeping roots whereas the M. sativa ssp. sativa type has contributed more to productivity.
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