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Soil amelioration methods tested in frost mitigation trial

Andrew Ware says frost damage is particularly problematic on sandy soils across Eyre Peninsula.
Photo: GRDC

Strategies to counter frost damage have been investigated on the Eyre Peninsula since 2022 and already the project has made a striking finding.

Of the strategies trialled, it was soil amelioration techniques using the Bednar Terraland Ripper that alone achieved outstanding outcomes. In one high-frost-risk zone, soil amelioration saw yields increase from 0.5 tonnes of wheat per hectare to 4t/ha, with the finding currently being validated through additional trials underway in 2023.

The project arose through the National Grower Network (NGN) and the Southern Panel in response to extensive damage to the Eyre Peninsula’s cropping program due to frost events between 2019 and 2020. The resulting project is led by Dr Andrew Ware, director of EPAG Research, in conjunction with local grower group Agricultural Innovation & Research Eyre Peninsula (AIR EP).

Mr Ware says frost damage is particularly problematic on sandy soils across Eyre Peninsula. The region has no domestic feed industry and cutting crops for hay results in costs of $50 to $60 per tonne to truck the hay to markets. The problem is compounded by low wool and lamb prices, which disincentivises growers from operating mixed-farming systems.

“In 2021, we ran a small trial in a frost-prone area to compare varieties with different phenologies and, therefore, different flowering times,” Mr Ware says. “However, the area experienced over 30 frost events and it proved very difficult to escape frost.”

The following year, the NGN project was launched. It uses a fully ground-up approach that integrates growers’ experiences through collaborations with a network of local consultants. This extends to understanding the cost-benefits associated with frost mitigation strategies.

Soil amelioration trial

The soil amelioration demonstration was established at Tooligie Hill Road on both a high and a moderate-frost-risk site. The high-risk site can experience more than 20 frost events in a season, even if conditions deliver a lot of cloud cover and rainfall.

Measurements taken at these sites started with soil chemistry and moisture levels at sowing. The timing of various growth stages was noted, along with soil and canopy temperatures. Moisture in the topsoil was additionally measured following a frost event. Finally, harvest cuts, yield and grain quality were assessed.

The demonstration compared ripped versus non-ripped replicated strips, with the soil amelioration undertaken to a depth of 40 centimetres using a Bednar Terraland Ripper.

“The thinking behind bringing subsoil to the surface is to prevent the otherwise sandy topsoil from reflecting heat and exacerbating the likelihood of frost damage,” Mr Ware says. “Additionally, it disrupts non-wetting properties of the soil, allowing the soil to hold more moisture, which acts to increase soil temperature.”

This rationale was validated by measurements taken at the Tooligie site where temperatures were 0.5 to 1.0oC higher during frost events on the ripped soils.

“We will run the trial again in 2023 to confirm these findings,” Mr Ware says. “Soil amelioration is taking off with growers for a number of reasons, and we are keen to determine whether frost mitigation can be confidently added to the expected benefits.”

Phenology trial

In addition, phenology and crop nutrition trials were undertaken at the Kay Road site.

Once again, Mr Ware found it impossible to escape frost damage by changing the flowering time. The most promising finding from the varieties tested is that barley withstands frost substantially better than wheat. Similarly, altering potassium and copper rates had no impact.

In addition, growers expressed an interest in testing nutritional products that purport to change the physiology of frost-nucleating bacteria, thereby acting to prevent freezing. The 2022 trials found that none of these products worked.

Mr Ware says despite these phenology trial results, the Frost Tactics Steering Committee will pursue additional phenology research in 2023. This work will especially focus on the new longer-season wheat varieties, such as Mohawk, Denison (PBR) and Longsword (PBR).

Early findings indicate a potential to reduce frost risk where Denison was mixed with varieties such as Vixen (PBR) and Scepter (PBR). Yield improvements of about 1t/ha were observed, which provides a useful level of frost mitigation.

“We need to know how these longer-season wheats perform over a range of seasons,” Mr Ware says. “The data of particular interest relates to yield margins relative to reductions in frost risk. An understanding of these dynamics would then allow the use of computer models to identify when it is beneficial for the grower to use these varieties and in what zones.”

More information: Andrew Ware,

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