Smoking out frost effects
On-farm trials in the central and southern wheatbelt in 2012 indicate stubble burning prior to seeding can reduce frost damage in wheat crops compared to stubble retention.
Although this research is based on only two sites, preliminary results show that where stubble was burnt, average yields were higher than in areas where stubble was left standing.
The theory is that stubble retention insulates the soil surface and prevents it from warming as much during the day as paddocks without stubble. This means less heat is radiated from the soil at night, which lowers the canopy temperature and leads to greater frost severity, duration and damage.
A 2012 Facey Group and Department of Agriculture and Food, Western Australia (DAFWA) trial with Wyalkatchem wheat in Wickepin found a 0.7 tonne per hectare yield advantage in burning stubble, high in the landscape (where there was moderate frost risk). There was a 0.3t/ha yield advantage in the lower (higher frost risk) part of the landscape.
DAFWA research officer Ben Biddulph says stubble retention increased the frost severity by lowering the minimum temperature by about 1°C to 2°C. It also increased the duration (of hours less than 0°C) of frost exposure in the canopy.
He says this corresponded with 10 to 15 per cent more frost-induced sterility (FIS) and greater yield loss, but the effects of frost versus chilling requires further examination.
On the back of a series of bad frost years, the Living Farm group initiated a trial last year in York, where 4ha of standing stubble was left in a burnt stubble paddock. This was designed to test local grower theories that stubble was playing a role in frost damage. One frost event at this site had temperatures below 0°C for nine hours.
Yield results are not published, but Living Farm research agronomist Rebecca Jenkinson says the burnt stubble area affected by frost had a higher yield, compared with the standing stubble areas affected by frost.
The burnt area spent fewer hours below 0°C during a frost and overall, had fewer hours below 0°C during the frost season.
To further investigate and validate WA stubble retention and frost research, the GRDC Regional Cropping Solutions Network (RCSN) groups in Kwinana West and Albany are funding a stubble management trial in each zone.
Treatments include plots where stubble is burnt, raked and retained to determine which is the least damaging for wheat during frost events.
The GRDC is also funding ConsultAg director Steve Curtin to repeat crop-grazing trials in the lower Great Southern region. This research aims to validate the results of 2012 trials funded by the RCSN Albany zone, which found grazing early and for a short period could reduce frost losses.
In a separate RCSN-funded project, Mr Curtin is looking at the effects and timing of foliar copper applications to mitigate frost damage in wheat crops at Lake Grace and Newdegate.
The Corrigin Farm Improvement Group is also exploring the relationship between nutrients and frost at its local trial site this year.
|Tiller number (m2)||FIS
|Burnt high in
|Burnt low in
high in the profile
low in the profile
Yield and yield components with the different treatments on Wyalkatchem wheat on a Wickepin property. Values are the average of 3 mean, LSD 0.05 estimated using a linear mixed model. Yield estimates are underestimates due to issues with a yield monitor sensor – but relative differences are representative. FIS is frost-induced sterility in the head.
Ben Biddulph, DAFWA
08 936 83431, email@example.com;
Rebecca Jenkinson, Living Farm
08 9641 2845, firstname.lastname@example.org;
Steve Curtin, ConsultAg
0427 651 626, email@example.com
The GRDC’ booklet Managing Frost Risk: A Guide for Southern Australian Grains:
End of Ground Cover Issue 105.
Read the accompanying Ground Cover Supplement: Spray application
GRDC Project Code SDI00019
Region West, National, North, South