Summary. 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, nitrogen (N)
concentration declined and calcium (Ca) concentration increased. Nitrogen and
Ca concentrations increased when young leaves produced from the summer flush
were sampled. Time of sampling produced the most consistently significant
(P<0.05) 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 stonefruit, was applied to
all Queensland sites and, as a consequence, mid lateral leaves contained
higher (P<0.05) Ca, magnesium (Mg) and chloride (Cl)
and lower (P<0.05) N and phosphorus (P)
concentrations than leaves from New South Wales sites. State effects can
therefore be interpreted as paclobutrazol effects. Cultivar effects
(P<0.05) 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 (Leece et al. 1971)
with the exception of lower Ca, lower Mg for New South Wales (both cultivars),
lower iron for Flordaprince (both states), higher P for Flordaprince in New
South Wales and higher manganese 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 (P<0.001), indicating that
the practice of heavy annual agricultural limestone or gypsum applications in
the absence of Mg fertiliser, which had been adopted by several growers in the
survey, is associated with lower leaf Mg concentrations.
Meteorological conditions, ozone concentration and leaf age affect gas exchange in Psidium guajava ‛Palumaʼ
