Crop development and leaf nitrogen in lychee in subtropical Queensland

Abstract

Heaviest flowering of 6-9-year-old lychee trees (Litchi chinensis cv. 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 prior to panicle emergence below 1.75-1.85% N to reduce vegetative flushing. Studies on the seasonal pattern of leaf nitrogen showed that the period during flowering to just after fruit set was the most stable for sampling for leaf nitrogen.