Kenton Porker1, James Hunt2, Michael Straight3
1 South Australian Research and Development Institute, Hartley Grove, Urrbrae SA 5064 firstname.lastname@example.org
2 Department of Plant, Animal and Soil Sciences, La Trobe University, 5 Ring Rd, Bundoora VIC 3086
3 FAR Australia, 4/97-103 Melbourne St, Mulwala NSW 2647
Early sown slow developing wheats offer increased biomass accumulation, grain number and thus potential grain yield. However, the greater vegetative growth of early sown crops can result in low harvest index (HI). We evaluated management strategies to improve HI in three early sown winter wheat cultivars using four experiments conducted across south eastern Australia. Strategies included low stand densities (30-50 plants/m²), defoliation, and deferred application of nitrogen fertiliser. We found low stand densities had a small positive effect on HI and grain yield. Defoliation tended to increase HI and but also reduce yield (depending on cultivar) due to reduced biomass which negated much of the increase in HI. Deferring nitrogen had a variable effect depending on starting soil N and timing of in-season rain to allow crop uptake of top-dressed N. The management factors studied here have some potential for improvement of HI but responses were variable and with small effect sizes. We conclude that genetic improvement is required to raise HI and yield in early sown wheat.