Diagnostic leaf nutrient standards for low-chill peaches in subtropical Australia.
Huett, D. O.; George, A. P.; Slack, J. M.; Morris, S. C.;
Australian Journal of Experimental Agriculture Year: 1997 Vol: 37 Issue: 1 Pages: 119-126 Ref: 18 ref.
1997
บทคัดย่อ
A leaf nutrient survey was conducted of the low-chill peach cultivars Flordaprince (October maturing) and Flordagold (mid November-early December maturing) at 3 commercial sites in both northern New South Wales and southern Queensland. Recently mature leaves from the middle third of a current season's fruiting lateral (spring flush) were sampled at stone hardening and 2 weeks postharvest and of a non-fruiting lateral at maturity of the summer flush (after summer pruning) during the 1992-93 and 1993-94 seasons. At an additional site in New South Wales (Alstonville), leaf nutrient concentrations were also determined on cv. Flordagem (early November maturing) at 2-week intervals during both seasons. Soil (0-30 cm) chemical determinations were conducted at all sites at 2 weeks postharvest. Seasonal trends in leaf nutrient composition were associated with a leaf age-maturity effect. As flush leaves matured during spring, and as mature leaves aged after hardening of the summer flush, N concentration d
eclined and Ca concentration increased. N and Ca concentrations increased when young leaves produced from the summer flush were sampled. Time of sampling produced the most consistently significant main effects on leaf nutrient concentration. The 2-week postharvest period was selected as a convenient time to sample (when leaves were of a consistent age and maturity, and the effect of crop load on tree nutrient reserves was still present). Paclobutrazol, which reduces vegetative growth in stone fruit, was applied to all Queensland sites and, as a consequence, mid lateral leaves had higher Ca, Mg and Cl and lower N and P concentrations than leaves from New South Wales sites. State effects can therefore be interpreted as paclobutrazol effects. Cultivar effects occurred for many leaf nutrients, however, at the 2-week postharvest sampling, concentrations were sufficiently similar to combine as a narrow adequate concentration range for both cultivars. The diagnostic adequate leaf nutrient concentrations were within
the range developed for high-chill peaches with the exception of lower Ca, lower Mg for New South Wales (both cultivars), lower Fe for Flordaprince (both states), higher P for Flordaprince in New South Wales and higher Mn values for Queensland (both cultivars). Regression analyses were conducted between leaf and fruit nutrient concentrations and soil chemical properties. The only consistent result demonstrated that as the soil Ca:Mg ratio increased, leaf Mg concentration decreased exponentially, indicating that the practice of heavy annual agricultural limestone or gypsum applications in the absence of Mg fertilizer, which had been adopted by several growers in the survey, is associated with lower leaf Mg concentrations.