ISHS Acta Horticulturae 275: International Symposium on the Culture of Subtropical and Tropical Fruits and Crops
NUTRITIONAL STUDIES ON LYCHEE TREES IN SUBTROPICAL AUSTRALIA |
| Authors: | C.M. MENZEL, D.R. SIMPSON |
| Abstract:
The most recently matured leaf behind the vegetative flush or fruiting cluster (flowering trees) was sampled monthly over 3 years in 7 lychee orchards (Litchi chinensis Sonn. cvs. Tai So, Haak Yip and Wai Chee) in subtropical Australia (Lat. 27°S). The concentrations of most nutrients were stable from the maturation of the late summer/early autumn vegetative flush of growth to panicle emergence or just after in winter (May-August). Levels of N, P, Mn, Zn and Cu were generally higher during this period and levels of K, Ca, Mg and Fe generally lower compared to South African standards. Tentative standard levels for Australian lychee orchards during May to August are: 1.50–1.80% for N, 0.14–0.22% for P, 0.70–1.10% for K, 0.60–1.00% for Ca, 0.30–0.50% for Mg, 50–100 ug/g for Fe, 100–250 ug/g for Mn, 15–30 ug/g for Zn, 10–25 ug/g for Cu, 25–60 ug/g for B, <500 ug/g for Na and <0.25% for Cl. Heaviest flowering of 6–9 year old lychee trees (Tai So) over 3 seasons in subtropical Queensland (lat. 27°S) was associated with a growth check in the terminal shoots prior to panicle emergence (May-June). Leaf nitrogen was the main factor controlling the level of flushing before panicle emergence. Flushing was active (on >40% of terminal branches) when leaf nitrogen concentration exceeded 1.85% N in April. These results suggest that flowering of lychee in subtropical environments where heavy rain precedes panicle emergence in autumn can be promoted by restricting leaf nitrogen levels below 1.75–1.85% N prior to panicle emergence to reduce vegetative flushing. | |
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