Caption: Wheat emerging at Mullewa when sown less than 100mm deep.
Caption: Wheat struggling to emerge at Mullewa when sown deeper than 100mm.
Research has confirmed the importance of avoiding smaller-sized seed when deep sowing wheat and that some varieties are better suited to the practice than others.
Growers will sometimes sow wheat seed deep when the topsoil is dry to give the seed a better chance of contacting moist soil at depth, or to avoid pre-emergent herbicide damage to emerging crops.
Department of Agriculture and Food (DAFWA) researcher Bob French last year conducted deep sowing research supported by the Grains Research and Development Corporation (GRDC).
The trials were conducted on sandy and loamy soils at Buntine, Merredin and Mullewa.
“One of the research findings was that wheat crop emergence from deep sowing improved when large seed was used, as seed size affects the length of the coleoptile – which covers the emerging shoot,” Dr French said.
“At Buntine, seed size did not affect crop emergence and yields when wheat was sown at 40mm, but small wheat seed reduced yields by an average of 12 per cent when sown deep at 75mm.
“We recommend that growers only use seed bigger than 35g/thousand seeds – or seed which will not pass through a 2.5mm screen - when sowing deep to chase moisture.”
Dr French said samples of wheat grown in WA’s eastern grainbelt in 2014 showed that most wheat seed from this region was at least 35g/thousand seeds.
“Of 173 samples taken, only 15 had thousand-seed weights less than 35g,” he said.
Dr French said the research also confirmed that wheat varieties with longer average coleoptile lengths had better crop emergence when sown at depth compared with varieties with shorter coleoptiles.
More information about coleoptile lengths for different varieties is available in the 2015 Wheat Variety Guide for WA.
Dr French said some growers considering deep sowing of wheat might be asking: ‘how deep is too deep?’
“Based on WA trial results on sandy and loamy soils, growers can expect to achieve reasonable crop emergence when sowing wheat to a depth of 80 to 100mm, as long as they’re using long-coleoptile varieties and larger seed,” he said.
“But it is taking a risk to go deeper than 100mm.”
The research conducted by DAFWA was funded by the GRDC project ‘Wheat agronomy – building system profitability in the western region’ which provides decision support information annually to improve the profitability of wheat growers in WA.
More information about sowing depth is available in the GRDC Wheat GrowNote.
Bob French, DAFWA
08 9081 3111
Natalie Lee, Senior Consultant, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code