Improved potassium access bolsters grain yields

Inversion tillage shows potential to boost yields on water repellent soils

Water Resources
A five-year trial has shown that inversion tillage has potential to boost grain yield potential on water repellent soils. PHOTO Jo Fulwood

A five-year trial has shown that inversion tillage has potential to boost grain yield potential on water repellent soils. PHOTO Jo Fulwood

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Five-year trial on water repellent soil shows inversion tillage can boost crop yields.

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Inversion tillage has the potential to boost grain yield potential on water repellent soils by providing better access to soil potassium, according to research by the Western Australian Department of Primary Industries and Regional Development (DPIRD).

The research was profiled at the 2019 GRDC Grains Research Updates.

DPIRD research officer Dr Craig Scanlan says the results from a five-year, GRDC-invested trial including wheat, barley and canola on a water repellent grey sand at Badgingarra, WA, showed the influence of soil potassium supply increased as the years progressed.

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"We found the subsoil in the rotary spader treatments was more wettable than the untreated control," Dr Scanlan says.

"This allowed the soil profile to wet more evenly and enabled crop roots greater access to soil potassium.

"The yield benefit from rotary spading varied from year to year, from 20 per cent in the second year to 55 per cent in the fourth and fifth year."

We found the subsoil in the rotary spader treatments was more wettable than the untreated control. - DPIRD research officer Craig Scanlan

Analysis showed the yield response was closely related to shoot potassium concentration in the last two years.

The experiment was designed to examine whether rotary spading changed the effect of phosphorus and potassium fertilisers in the years after it was applied.

Analysis of the five years of data from the Badgingarra site showed no differences in the residual effect of phosphorus and potassium fertiliser.

Dr Scanlan says the research suggested addressing the soil constraint was of greater importance than changing the potassium and phosphorus fertiliser strategy.

"The results also showed soil potassium gradually depleted over the five years for all treatments, while water repellence in soils that had rotary spader treatments reverted back to a moderate level," he says.

More information: Dr Craig Scanlan, DPIRD, 08 9690 2174, craig.scanlan@dpird.wa.gov.au

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