Nutrients under scrutiny as a defence against frost

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Photo of Professor Richard Bell (left) and Dr Qifu Ma

Murdoch University researchers Professor Richard Bell (left) and Dr Qifu Ma in National Frost Initiative trials at Aldersyde, near Narrogin, WA. Preliminary research has shown increased potassium reduced frost-induced sterility in wheat by eight per cent.

PHOTO: Sue Knights

Preliminary trial results (Year 1) have shown the value of better potassium nutrition as a possible defence against frost in crops grown on low to moderate potassium soils.

GRDC-supported research, led by Murdoch University’s Professor Richard Bell, is assessing how better potassium and trace element nutrition could make wheat and canola more tolerant to frost.

He says wheat is most susceptible to frost damage during and after flowering, but yield losses may be minimised by selecting more frost-tolerant varieties and applying proven agronomic management practices.

Potassium is the focus of the research, which is only into its second year, because overseas studies have shown that high concentrations of potassium in plant tissue may protect a crop from frost damage.

“Potassium boosts photosynthesis, impairs the formation of toxic reactive oxygen species at low temperature and maintains cell hydration under freezing and drought stress,” Professor Bell says.

“Micronutrients such as copper, zinc, manganese and molybdenum may also improve crop tolerance to frost damage by promoting photosynthesis, antioxidant enzyme activity, membrane stability, cell hydration and pollen development.”

To test this, in 2015 Professor Bell and his team set up trials on two frost-susceptible sites – one with wheat and the other with canola – near Narrogin, Western Australia.

Laboratory tests indicated the potassium status of the soil at both sites was low to moderate.

At the wheat site, the researchers used four different sowing dates: 15 April, 29 April, 15 May and 2 June. The first two times of sowing were irrigated to ensure germination, but for the third and fourth times of sowing there was enough rainfall for germination.

At the wheat site, the researchers tested Mace and Wyalkatchem. Mace is considered less sensitive to frost and Wyalkatchem more sensitive to frost.

Tested against a control of nil potassium were 80 kilograms per hectare of potassium at sowing and 80kg/ha of potassium at sowing plus foliar trace elements (copper, zinc, manganese and molybdenum) applied in late July.

Sterility reduced

For the 29 April and 15 May sowings, Professor Bell says potassium reduced the amount of frost-induced sterility in wheat by about eight per cent, but the foliar trace elements and variety choice had no impact on frost-induced sterility.

“It’s the first evidence we have that improved potassium nutrition could make a difference,” he says.

“The levels of potassium in plants were not below the critical level and didn’t appear to be deficient, but the extra potassium applied at sowing does seem to have made them more tolerant to frost.”

At the canola site, the researchers were interested in finding out whether potassium applied to wheat in 2014 would reduce pod abortion in canola in 2015.

To do this, the wheat planted in 2014 was fertilised with either nil potassium at sowing or 80kg/ha of potassium at sowing with magnesium and calcium drilled into the subsoil.

In 2015, the canola variety ATR-Snapper was tested at one time of sowing on 22 April.

The only additional treatment was foliar boric acid, copper sulfate, manganese and zinc sulfate applied in late July.

For the canola, when flowers were exposed to multiple severe frosts in early and mid-September there was 50 per cent pod abortion of the control plants, compared with 30 per cent abortion in the treatment of potassium plus foliar trace elements.

While Professor Bell sees potential for using fertiliser management as a tool to reduce grain yield losses caused by frost, he says the results only represent a single year of evidence in one district.

“We have established similar trials through the GRDC’s National Frost Initiative at other sites this year with wheat to confirm if the results are repeatable,” he says.

“Our trials are also examining the response of frost-induced sterility to rates of potassium and trace elements, and assessing the profitability of applying lower potassium rates and foliar potassium close to flowering.”

More information:

Professor Richard Bell,
0405 131 429,
r.bell@murdoch.edu.au

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GRDC Project Code UMU00042, UMU00046

Region West