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 (Litchi 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/kg, to determine the effect of time of N application on leaf N concentration, vegetative growth, flowering, and yield. Applications of N (equivalent 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. Control trees received no N. Leaf N concentrations in April-June were, on average, about 0.1% lower after a single N application in winter than application in summer or split applications. Leaf N concentrations in November-February were about 0.1% higher after winter or split N applications than after summer applications. Timing of fertiliser application had no affect on yield. It took 4 years without N fertiliser to show significant reductions in yield compared with fertilised trees. In year 4, yield increased from 20 to 60 kg/tree on individual pairs of trees as leaf N in August increased from 0.95 to 1.56%. Lower yields in control trees in year 4 were associated with poor leaf growth in the previous 2 years, and with lower concentrations of N in the panicles, leaves, twigs, and small branches, as well as lower chlorophyll concentrations and net CO2 assimilation after fruit set, compared with trees receiving N.