Defining seedling specifications for Eucalyptus globulus: effects of seedling size and container type on early after-planting performance

Large and small seedlings (early- and late-germinated, respectively; with a two-fold height difference) were raised in Colmax® 72 (volume 45 mL, 50 mm deep), Premium Plastic 104® (volume 85 mL, 73 mm deep) and Lannen® 63 (volume 115 mL, 90 mm deep) containers in the Western Australia Plantation Resources (WAPRES) nursery, Manjimup, Western Australia (WA). The seedlings were planted into field trials at 'Oldhams' treefarm, a site near Manjimup (WA) considered of high risk to spring beetle attack, and at 'Capaul', 'Knebsworth', and 'Stribling' treefarms in the 'Green Triangle' (GT) region of western Victoria, Australia. The trials in the GT traversed an estimated production gradient that was strongly linked to average rainfall. At all sites, seedling height and diameter (and leaf area loss to spring beetles at Oldhams only) were assessed at planting and at 2, 4 and 6 mo after planting. Seedlings were harvested at 4 mo at Oldhams and at 2 and 4 mo in the GT trials for nitrogen and biomass analysis. Six months after planting, mortalities ranged from 0 to 2.5% in the GT trials, and from 4 to 11% at Oldhams, and were not related to nursery treatment. There was no effect of initial seedling size on growth 6 mo after planting, but a strong effect of container type in all GT trials. At Oldhams there was no effect of seedling size but there was an effect of container type at 6 mo after planting. In the GT trials, biomass and height growth at 6 mo was least in Colmax 72-raised seedlings, intermediate in Lannen 63-raised seedlings and greatest in Premium Plastic 104-raised seedlings. The performance of seedlings raised in Colmax 72 containers planted into the GT trials may be related to the effects of the small container size on root architecture and/or seedling nutrition. The intermediate growth of seedlings raised in Lannen 63 containers, that had the largest container volume, indicates that factors other than container volume affect seedling performance.