Seed size makes major difference to herbicide resistance
CROP competition is an important strategy in the Weedsmart 10 Point Plan to manage herbicide resistance – but it’s not all about row width and seeding rate – the size of the seed sown makes a difference too.
Rohan Brill, Research and Development agronomist, NSW DPI, based in Wagga Wagga, along with colleagues at Trangie and Tamworth, has been teasing apart whether the improved early performance of canola hybrids over open-pollinated (OP) cultivars comes from the generally-larger seed size of hybrids or from hybrid vigour.
“It seems that most of the improved early growth in hybrids lies in the larger seed size, with heterosis providing an additional benefit,” he said.
“Our study showed that sowing large canola seed, regardless of the cultivar, is key to strong early crop growth and the crop’s ability to compete with weeds.”
As a reliable rule of thumb, Mr Brill recommends cleaning and grading all farmer-retained OP canola seed to collect planting seed that is 2mm in diameter or larger.
In both glasshouse and field experiments following this rule led to improved open-pollinated TT canola emergence and early biomass production.
Seed size had a greater effect on early biomass production than did cultivar type (hybrid vs OP).
“A 10 per cent difference in seed diameter produces a 33 per cent difference in seed volume, so it is very important not to skimp on the 2 mm diameter rule,” he says.
For more information about managing herbicide resistance visit the Weedsmart website www.weedsmart.org.au.