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Researchers work to develop pastures suited to WA's eastern wheatbelt

Clint Butler inspects the results of the rhizobia-coated vetch trial on his Narembeen property in Western Australia.
Photo: Evan Collis

Researchers are on a quest to develop a portfolio of pastures suited to Western Australia's eastern wheatbelt region - providing growers with more pasture options on heavy-textured alkaline soils.

GRDC-invested trials on the property of Clint, Kim and Sue Butler, of Narembeen, are giving one of the first positive indications that vetch could be an opportunity to diversify out of medic pastures on tough soils in the low-rainfall region.

The Butlers have regenerating medic pastures and have also been sowing Bartolo bladder clover on their heavy soils for the past few years, but Clint says the biomass potential of the medic plant is very limited and the feed value is low.

"In our tough conditions, the medics can't get their roots down enough to produce the biomass that we need - not only for livestock feed, but also for the nitrogen fixation in the soils for future cereal crops," Clint says.

"We now also need a pasture legume that can reduce nematode numbers, or other soil-borne diseases, and we are hoping vetch will be the answer to that."

Researchers trial vetch varieties

While long-season vetch has been grown for many years in WA's south-eastern coastal region, it is yet to find a stable home in the eastern wheatbelt.

Researchers from Murdoch University's Centre for Rhizobium Studies are trialling a range of vetch varieties on the Butlers' property and also comparing early and late-sown vetch with medics, chemical fallow and a barley crop - measuring nematode numbers, soil nitrogen values and soil moisture values throughout the season.

The trials will also track the yields and protein of subsequent crops to determine the benefits of pasture legumes in the whole cropping rotation.

Clint has already seen the success of subsequent cereal crops after growing a serradella pasture legume on his lighter, more acidic soils, and hopes vetch can have a similar nitrogen impact on subsequent crops in his heavy soils.

"In 2019, we had a barley crop that followed serradella, and it only received 120 millimetres of growing-season rainfall, plus seven units of applied nitrogen, yet it yielded 1.8 tonnes per hectare, so we know this rotational strategy works for us," he says.

In 2020, the trials will all be planted to wheat, which will clearly demonstrate whether vetch can provide a free-nitrogen system, at least in the first year.

Centre for Rhizobium Studies research officer Rob Harrison says growers in the region were very interested in finding a legume pasture alternative to medics for this particular soil type.

"At all our field days, growers were very interested in the potential of vetch, and early indications are that it grows well on these heavy soils," Mr Harrison says.

"Early sown vetch was a clear winner in terms of biomass production and, despite no rain for almost six weeks, it produced 1t/ha more biomass than the late-sown vetch."

At all our field days, growers were very interested in the potential of vetch, and early indications are that it grows well on these heavy soils. - Centre for Rhizobium Studies research officer Rob Harrison

GRDC Research Code UMU1805-001RMX

More information: Rob Harrison, r.harrison@murdoch.edu.au

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