In-season agronomic manipulation of early sown spring wheat; to delay flowering and reduce frost effects – Wagga Wagga 2023

Abstract

Key findings • This study showed it is possible to reset the flowering time for early sown quick–mid spring wheat varieties through in-crop mechanical defoliation, apical pruning, during early stem elongation (GS31–32). • Depending on the intensity of the defoliation treatment, anthesis, was delayed by up to 25 days for Scepter[PBR] from a 5 April sowing date (SD), which resulted in a significant increase in yield compared with the undefoliated control at 5.49 t/ha vs 4.31 t/ha. • The heavy defoliation treatment enabled Scepter[PBR] to reach anthesis on 25 September from the 5 April sowing, around the start of the optimum flowering period (OFP) for this environment, as opposed to the untreated control, which flowered on 31 August. • Although apical pruning was shown to increase the yield potential of early sown quick–mid spring wheats, it was still not able to out-yield Illabo[PBR], a locally well adapted mid winter wheat variety sown in its preferred sowing window, which achieved the highest yield of 7.40 t/ha. • The best performing heavily defoliated Scepter[PBR] was only able to achieve 89% (5.49 t/ha) of the yield from Scepter[PBR] sown in its preferred sowing window (6.19 t/ha). • Yield potential tends to be optimised when the correct phenology type is sown in its preferred window, so that it flowers within the OFP for a given environment. • Apical pruning should only be considered as a possible management strategy when quick–mid spring wheats have been sown well outside their preferred window and/or are developing such that there is an increased risk of yield loss due to frost risk.