DRY conditions before and after sowing in the Mallee have been identified as as the most common cause of poor canola yields.
Growers in the survey had sown 25,156ha of canola, averaging 600ha a farm.
The landholders reported that about 20 per cent of canola sown did not establish successfully although no remedial action was taken on most of this area. Another 35 per cent was resown to canola and 9 per cent was resown to wheat.
Mallee CMA chairwoman Sharyon Peart said many Victorian Mallee farmers struggled to establish their canola crops last year.
"In 2011 (we) saw a rapid increase in the area of the Mallee sown to canola, however problems with poor crop establishment cost canola growers millions of dollars," she said. "This also increased the risk of wind erosion as there was little ground cover to protect the soil surface."
Establishment problems were most common and severe on sand hills and rises and on light sandy soils. Flats with clay soils and summer weeds sites were also frequently associated with poor establishment.
Dodgshun Medlin research and development leader Ivan Mock said dry surface soils at sowing - identified by farmers as the most common and most serious influence on poor establishment - delayed germination and increased the length of exposure to mice damage.
Mr Mock said this was exacerbated on sands with low water-storage capacity and clays with reduced water availability to plants.
Mice and rabbits, as well as heavy stubble and associated seeding depth control, were also frequently associated with poor establishment.
The survey found 16 per cent of farmers thought sowing time was a factor, although the average difference between good and poor emerging crops was 1.5 days and only two growers sowed after May 4.
Those surveyed indicated they planned to reduce the area under canola by 10 per cent this year, which would make it the second largest canola planting in the Mallee.
Mr Mock said agronomic practices that increased moisture available to the canola seed would reduce establishment problems.