But this week, Grains Research and Development Corporation’s will release results of trials which tested whether deep ripping and mouldboard ploughing can increase crop yields and reduce the severity of frost.
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 GRDC Grains Research Update this week at Crown Perth.
Frost will be the focus of an interactive Focus Session to be held on February, with Knell among those on the panel for the session.
While methods such as deep ripping followed by spading or mouldboard ploughing have been shown to overcome the water repellence of sandy soils, 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.
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,” 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.”
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.”
