DRIER growing season starts have opened the possibility of deep seeding wheat to reach moisture for farmers in the lower rainfall areas.
But that has been trickier to achieve since the introduction of dwarf wheat varieties into the commercial market has not only shrunk the height and mass of wheat crops in WA but also the plants’ coleoptile.
The coleoptile, a pointed protective sheath covering the emerging shoot of a wheat plant, is much smaller in the dwarf wheats.
To better understand the interaction, Department of Primary Industries and Regional Development Merredin senior research officer Bob French’s trial at this year’s Liebe Spring Field Day, Kalannie, sought to characterise the effect of genetically determined differences in coleoptile length on wheat response to deep seeding.
“Recent climatic trends in WA coupled with advances in cropping technology mean growers want to establish crops earlier in the season than traditionally,” Dr French said.
“Higher temperatures and less frequent rainfall in early autumn mean that the soil surface can dry very quickly at this time of the year which means ideal seedbed conditions for the crop establishment can be short-lived.
“One way to overcome this constraint would be to place seed deeper in the soil where moisture levels are more stable after rain, but there is a limit to the depth from which a seedling will emerge.”
Most modern Australian wheats contain the dwarfing genes Rht1 and Rht2, which shorten the coleoptile and therefore don’t emerge from deep sowing as effectively as older cultivars.
“However there are alternative dwarfing genes that don’t shorten the coleoptile and using these instead may retain the agronomic advantages of semi-dwarf wheats while enabling deeper sowing,” Dr French said.
Using the widely adapted Australian tall wheat, Halberd, which contains no dwarfing genes, the trial results clearly shows the superior ability of Halberd to emerge from deep sowing.
“Amongst modern cultivars tested Cutlass and Magenta were best,” Dr French said.
The data suggested that Emu Rock, Halberd and Magenta, with the Rht1 gene emerged well from depth, but this is not consistent with other years tested.
Dr French concluded that many modern wheat cultivars establish poorly when sown 100 millimetres deep, but there are genetics available which will improve establishment from deep sowing while retaining other agronomic advantages of semi-dwarf wheats.
“There is potential to improve the emergence of wheat sown as deep as 100mm which should make very early sowing less risky,” Dr French said.