Trials probe impact of soil amelioration on frost

Author: Natalie Lee | Date: 24 Feb 2017

The Brookton trial site after it had been spaded, left, compared with the control plot.

The Brookton trial site after it had been spaded, left, compared with the control plot. Photo by Garren Knell, ConsultAg.

The results of trials testing whether deep ripping and mouldboard ploughing can increase crop yields and reduce the severity of frost will be revealed at Western Australia’s premier grains research forum.

Agronomist Garren Knell from ConsultAg helped conduct large-scale field trials of soil amelioration methods at Brookton and Corrigin in 2014 and 2015, and the results will be among the frost research discussed at the Grains Research and Development Corporation’s (GRDC) Grains Research Update, Perth.

The 2016 cropping season in Western Australia was impacted by severe frosts over a protracted period resulting in significant losses for growers in some regions.

GRDC’s premier annual grains industry event is being held at Crown Perth on February 27 and 28 and frost will be the focus of an interactive Focus Session to be held on day two of the event, with Mr Knell among those on the panel for this session.

While methods such as deep ripping followed by spading or mouldboard ploughing have been shown to overcome the water repellence of sandy soils, Mr Knell and others who conducted the soil amelioration trials wanted to investigate whether they also allow the ground to store more heat and release it later in the evening when frost occurs, mitigating the severity and duration of the frost.

In addition to Mr Knell, Trent Butcher, also of ConsultAg, Living Farm, the Department of Agriculture of Food (DAFWA) and local growers were involved with the trials, which were funded by the GRDC.

Mr Knell said crop yields increased at the trial sites in both years, through the removal of sub soil constraints, better crop establishment and increased yield potential, although 2014 and 2015 were years of minor frosts which made it difficult to see significant differences between the plots. 

“At Brookton the ripped and spaded treatment yielded 0.46 tonnes per hectare more than the untreated control in 2014 and 0.7t/ha more in 2015, on deep sandy duplex soil that was deep ripped to a depth of 50cm followed by spading to a depth of 40cm,” he said.

“At the Corrigin site the mouldboard treatments yielded 0.62t/ha more than the untreated control in 2014 and 0.61t/ha more in 2015, after ploughing duplex sand over gravel over clay to 40cm.”

Crop establishment was measured to determine the potential impact from different crop densities.

“Trial paddocks featured soil water repellence and a high history of frost events over the last ten years, and trials were sown using farmers’ broadacre seeding equipment and standard wheat cultivars, rotation and agronomic management,” Mr Knell said.

“With both years of trials delivering below average rainfall, the water capture and holding characteristics of the soil, which were changed under amelioration, become more important.

“The improved yield was consistent both high and low in the landscape with varying levels of frost damage, but the increase was attributed to amelioration alleviating the non-wetting and other sub soil constraints, rather than minimising frost damage.

“Results indicated that soil amelioration should not be carried out purely for frost minimisation, as there was no consistent reduction in frost severity or duration in ameliorated treatments compared to the untreated control.”

Mr Knell said there had been numerous anecdotal reports in frost years such as 2015 and 2016 of ameliorated soils resulting in higher yielding crops, but current work indicated this might be largely a result of increases in the yield potential of crops rather than a reduction in frost damage.

Financial gains were made on the soils within one year at the Corrigin site and two years at the Brookton site, despite low rainfall and slight frost damage in both seasons.

“This analysis estimated the soil amelioration treatments to cost less than $140/ha, although actual prices vary greatly depending on soil type, workability, contractor used, ownership and operating and maintenance cost of equipment.”

The trials were funded by the GRDC National Frost Initiative (NFI) which combines research into reducing the susceptibility of crops to frost through genetics and breeding; assessing the impact of different management practices on frost severity; improved understanding of environmental and landscape variables on frost severity and more.

In addition to Mr Knell, experts on the interactive Frost Focus Session panel during the GRDC Grains Research Update, Perth, will include Ian Foster and Ben Biddulph, both of DAFWA, Nik Callow, of The University of Western Australia, and Juan Juttner, of the GRDC.

The GRDC Grains Research Update, Perth, will feature wide-ranging information, interactive sessions and latest grains research results from more than 50 presenters and five international speakers.

This event will be complemented by one-day GRDC Grains Research Update events to be held in regional areas to enable growers to access a subset of the available information of particular relevance to their region.

To register or for more information about the Update events, go to the Grain Industry Association of WA
or contact the event coordinator on 08 6262 2128 or email

Contact Details

For Interviews

Garren Knell, ConsultAg
0427 442 887


Natalie Lee, Cox Inall Communications
0427 189 827

GRDC Project Code DAW00241

Region West