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The role of lucerne in crop-pasture systems in the wimmera

T.M Young, W.K Gardner, M. Drum, J. Carter' and T. Lewis

Department of Agriculture, Victorian Institute for Dryland Agriculture Wimmera Research Station, Private Bag 260, Horsham VIC 3401
Department of Conservation and Environment, PO Box 487, Horsham VIC 3400

The restorative powers of pasture legumes (soil structure, fertility) have long been recognised and exploited in cropping rotations throughout the Wimmera and Mallee. Since the mid 1940s producers have relied on annual medics (Medicago truncatula) as the major pasture component, rejecting lucerne (Medicago sativa) as difficult to establish and too inflexible for convenient use in short-term pastures. Poor returns from medic pasture-based livestock enterprises have seen them largely displaced from farming systems by grain legumes; a change which over the last two decades has been accompanied by declining soil fertility and soil structure.

Methods

Stock carrying capacity on wheat-sheep farms using lucerne-based pastures was monitored on selected properties across the Wimmera-Mallee region.

At Minyip in the eastern Wimmera, a four-year lucerne grazing trial was established.

Forty hectares adjacent to a saline gully at Marnoo in the south-eastern Wimmera was sown to lucerne and water-table movements monitored.

Results and discussion

The regional survey revealed that lucerne-based pastures supported stock numbers consistently 60% higher those that achieved on annual medic-based pasture. This finding was supported by the results of the Minyip grazing trial. Merino wethers stocked at 6.25 a hectare were maintained at 70 kilograms liveweight and produced 54 kilograms of wool a hectare.

Higher and more even seasonal distribution of lucerne dry matter production explains in part this result. At least as important are the changes to rotations necessary for successful lucerne pastures and the resultant provision of a better feed base for livestock.

In the Marnoo salinity trial, lucerne has lowered moderately saline watertable (12000 uS/cm) to a depth some two to three metres below that found under conventional crop-pasture rotations in adjacent land.

The introduction of lucerne into crop-pasture systems throughout the Wimmera-Mallee region has the potential to substantially improve the profitability of livestock enterprises, whilst addressing emerging problems of dryland salinity, declining soil fertility and deteriorating soil structure.

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