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Pasture legumes offer protein boost for subsequent cereals

Ardath, Western Australia, grower Phillip Foss says pasture legumes have long shown their value in his cropping rotation.
Photo: Evan Collis

While yield might be king, high protein levels in wheat crops can also add to the annual farm budget.

Ardath grower Phillip Foss has long seen the value of pasture legumes in his cropping rotation in terms of increased cereal yields. But data from trials on his central wheatbelt property are also illustrating the importance of pasture legumes to cereal protein levels.

The research, undertaken by Murdoch University's Centre for Rhizobium Studies, is putting cereal crops under the microscope to better understand the plant's response to biological soil nitrogen resulting from a pasture legume phase.

Twelve to 14 per cent protein levels measured in all wheat crops following serradella (sown in both February and May of the previous year), have further confirmed the financial upside of including pasture legumes in a cropping system - despite a dry summer and autumn season.

Protein levels provide confidence

According to Centre for Rhizobium Studies research officer, Robert Harrison, these high protein results should give growers more confidence to plant both summer-sown (hard-seeded serradella in pod) and autumn-sown (scarified serradella seed) in their rotations -regardless of summer rainfall patterns.

Mr Harrison says some soil moisture is required during the warmer summer and autumn months to activate soil microbes to begin the natural feedback model of the nitrification process following a pasture legume crop.

Given the dry start and finish to the 2019 season, he says, yield results from the wheat treatments following the serradella were disappointing - but expected.

"The stand-out result was the ability of the wheat crop to utilise the small amount of available nitrogen that had been fixed in the soil to improve grain protein," Mr Harrison says.

He says nitrogen from the 2018 serradella treatments will release into the soils, ready to be utilised by subsequent cereal crops.

Multiple benefits from legumes

Phillip Foss has been planting serradella, biserrula and subclover for a number of years and says the benefits of pasture legumes are more than just a one-year grazing opportunity for his flock of 4000 sheep.

"We use pasture legumes in our system for a number of reasons, including weed control, early sowing opportunities, plus the benefits for subsequent cereal crops," Phillip says.

"Our cereals are always better following a serradella or biserrula pasture phase."

Phillip says the pasture legumes will always have a place in his rotation and he plans to increase his plantings of Margurita (PBR) serradella, which he says is an excellent fit for his business.

"The hard-seeded serradella allows us to start our seeding program in late summer, or early autumn, knowing the seed, which is encased in a pod (unscarified), will take several months to break down," he says.

"Because of its capacity to regenerate, we know we can have many years of crops from this one planting, which reduces the number of times we have to put the machines over the paddocks, thereby reducing our soil compaction issues."

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

GRDC Research Code UMU1805-001RMX

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