McDonald, GK1 and Hussein, S2
1The University of Adelaide, Waite Campus, PMB 1 Glen Osmond SA 5064 firstname.lastname@example.org
2Longreach Plant Breeding, Adelaide South Australia
The size and composition of seed varies considerable between sites and seasons and it is often suggested that plump seed with a high nutrient concentration will benefit yield. There have been few field experiments that have examined this idea critically. Experiments were conducted over three years at low and medium rainfall sites in South Australia to examine the relative effects of seed source and seed size on yield. Seed was selected from National Variety Trials (NVT) sites based on differences in grain nutrient concentrations and graded into two or three size categories. Grain nutrient concentrations varied considerably between sites and grading the seed did not influence seed nutrient concentrations. Seed source influenced yield in only two of the eight experiments and the effects of seed source varied with variety. The effect on yield varied from about 4% up to 28%. Seed P concentration was the nutrient most commonly associated with yield variation. Using large seed improved crop establishment and crop vigour but yield benefits of large seed were only achieved at higher yielding sites where the benefit was about 5%. When grain yields were less that 2 – 2.5 t/ha, there was no yield benefit from using large seed and in one instance yields were reduced. The results suggest that seed size has a smaller, but more consistent effect on yield compared to seed source, and the effects of seed source varied with variety. The benefits from improved seed quality were only achieved at sites where yields were higher than approximately 3 t/ha.