Stylos: The Broad Acre Legumes of N Australian Grazing Systems

Early accidental introduction of Stylosanthes humilis into the N Australian savannas in the early 20th century and its contrived spread by the late 1960s led to the release of more perennial types. Townsville Stylo, as it was known, colonised large areas and had reached its climatic and agronomic limits by the 1970s. It had a major impact on beef production in areas where natural carrying capacities were relatively low. The precedent of Townsville Stylo directed attention to the genus Stylosanthes. This impact continued until 1974 when anthracnose virtually wiped it out. Fortunately 2 other Stylosanthes species, S. hamata cv. Verano and S. scabra cv Seca, were released around that time. These extended the ecological range of adaptation of the genus and were adopted widely to improve dry season cattle nutrition and broaden the opportunities for economic beef production on naturally infertile seasonally dry landscapes. Verano and Seca remain the most widely used. During that period S. guianansis came and went for various reasons in the high rainfall areas. S. hippocampoides has found a niche on sandy subtropical soils. Two cultivars, Primar and Unica, of a new species, S. seabrana, have been released for cold tolerance and suitability to fertile soils. New anthracnose tolerant S. guianansis varieties Nina and Temprano are creating interest in the hay industry. Most stylo sowings have been into native vegetation. Up to 1995 it was estimated that 1.15Mha were planted to stylos. Since then another 350Kha (estimated from seed sales) have been planted, making a total of 1.5Mha. With natural spread, an area of up to 3Mha would have some stylo presence. Prolonged drought during this recent period has reduced the annual area planted. The improvements were estimated in 1996 to have added $20M/year to returns from cattle across N Australia, a figure that might be closer to $30M now