Canola growers whose plantings have established poorly have been cautioned that reseeding or patching out their crops were highly risky management options.
Department of Agriculture and Food research officer, Dr Mohammad Amjad, said such strategies were rarely profitable at this stage of the season.
"Marginal soil water conditions at seeding and poor follow up rains in May have resulted in poor and patchy crop establishment in some areas in the central and northern agricultural regions," he said.
Dr Amjad said decisions about re-seeding canola need to take account of the potential of the existing stand and the potential yield and quality of late seeded crops.
"Canola is a super flexible crop and normally compensates for variation in plant establishment," he said.
"Plant population between 50-90 plants per square metre should achieve potential yield between 1.4 – 1.8 t/ha in most circumstances."
Research by the Department on crop establishment showed patchy, uneven and poor establishments of 20-40 plants/m2 were generally adequate to achieve yield of 0.8–1.2 t/ha (80-90pc yield of a uniform established crop with 50 plants/m2).
Plant population of 10-20 plants/m2 could still be a viable option, albeit at a lower yield potential of about 0.4-0.6t/ha.
If canola emergence is between 4-6 plants/m2, the options of reseeding canola or seeding with other crops, such as wheat, is unlikely to be feasible or economical than keeping the status quo as fallow.
"With triazine tolerant (TT) varieties comprising 90pc of canola sowings, there are also not many crop patch-up options left for the canola sown paddocks, as cereals can not be sown because of high levels of triazine residues in the soil," Dr Amjad said.
He said it was important to count plant emergence in patchy areas and make an allowance for late emerging plants, before considering any future paddock management decisions for the crop, such as nitrogen fertiliser.
"Generally patchy and poor stands of early sown canola are agronomically and economically better than canola re-seeded later in the season," Dr Amjad said.