Apparently in antipodean Western Australia, sowing less canola seed may produce the greatest yield in dry areas.

The Department of Agriculture's Jeff Russell and Farm Focus Consultants' Angie Roe presented this apparent oxymoron to graingrowers at the 2004 Grains Research and Development Corporation supported Crop Updates.

Acknowledging that canola's thirst made it a riskier proposition in drier areas, they helped Kellerberrin growers experiment with seeding strategies which might give the plants a better chance. Trialing rates of six, four and two kilograms per hectare, they found yield and oil content climbed higher as seeding rates eased.

Ignore logic telling you that at 2 kg/ha the density of established plants would be only half that achieved when seeding at 4 kg/ha and one third that achieved at 6 kg/ha.

Instead, consider that those miserly plants sown at 2 kg/ha needed to share less of the available moisture and nutrients and so produced more pods.

The ‘podulation' grew from 474 pods per square metre at the high sowing rate to 1114 pods per square metre at the lowest rate. Unlike the plants themselves, which seem to contest available resources to their collective detriment, all the pods, irrespective of density, generally grew to the same size.

Ultimately, yield lifted by 90 kg/ha using the low seeding rate, equating to a $45/ha improvement in financial performance. This supports earlier research which advised that lower plant densities should be targeted in areas with yield potential below 0.8 t/ha.

Rates of 3-5 kg/ha are traditionally recommended for canola. With this in mind, growers in marginal canola climates should steer towards the sparse end of those rates.

The Crop Doctor is GRDC Managing Director, Peter Reading