In-season agronomic manipulation of early sown spring wheat to delay flowering and reduce frost impact – Wagga Wagga 2022

Abstract

Key findings •In-crop mechanical defoliation ‘apical pruning’ of early sown spring wheat during early stem elongation (Zadoks growth stage: GS31–32) was able to delay/reset anthesis by 8–25 days. •Apical pruning enabled the quick, mid spring cultivar Scepter[PBR], sown approximately 14 days earlier than its recommended sowing window, to flower in the optimal flowering period (OFP) for this environment as opposed to the untreated control, which flowered 8 days before the OFP. •Lack of abiotic stress factors, namely frost and heat, combined with adequate in-season rainfall in 2022 contributed to a yield advantage for early sowing dates. Scepter[PBR] for example, sown on 25 April (approximately 14 days earlier than the start of its optimum sowing window) yielded 7.24 t/ha. •Although it was possible to reset and delay anthesis so that it occurs within the OFP, delays in anthesis in response to apical pruning at GS31–32 were associated with either a decrease in grain yield and/or no significant increase in grain yield. •The yield penalties were greater when defoliation timing was delayed (e.g. GS32), and intensity increased (cut at 3–4 cm). •Reduction in grain yield in response to apical pruning was associated with reduced biomass accumulation at mid flowering (GS65). •Both yield and grain protein (GP) correlated with dry matter (DM) at GS65, highlighting nitrogen (N) application post apical pruning, to compensate for biomass, to achieve yield potential and targeted GP classification.