TIME OF NITROGEN APPLICATION AND YIELD OF BENGAL LYCHEE ON A SANDY LOAM SOIL IN SUBTROPICAL QUEENSLAND

Nitrogen (N) was applied over 4 years to B-year-old lychee trees (Litc hi chinensis Sonn. cv. Bengal) growing in subtropical Queensland (lat. 27 degrees S.) on a sandy loam soil (0-15 cm) with 2.8 mg nitrate-N/k g, to determine the effect of time of N application on leaf N concentr ation, vegetative growth, flowering, and yield. Applications of N (equ ivalent to 750 kg N/ha in year 4) were made after panicle emergence in July, after harvest in January, or split between the 2 periods. Contr ol trees received no N. Leaf N concentrations in April-June were, on a verage, about 0.1% lower after a single N application in winter than a pplication in summer or split applications. Leaf N concentrations in N ovember-February were about 0.1% higher after winter or split N applic ations than after summer applications. Timing of fertiliser applicatio n had no affect on yield. It took 4 years without N fertiliser to show significant reductions in yield compared with fertilised trees. In ye ar 4, yield increased from 20 to 60 kg/tree on individual pairs of tre es as leaf N in August increased from 0.95 to 1.56%. Lower yields in c ontrol trees in year 4 were associated with poor leaf growth in the pr evious 2 years, and with lower concentrations of N in the panicles, le aves, twigs, and small branches, as well as lower chlorophyll concentr ations and net CO2 assimilation after fruit set, compared with trees r eceiving N.