EFFECT OF FALL IRRIGATION LEVEL IN MAURITIUS AND FLORIDIAN LYCHEE ON SOIL AND PLANT WATER STATUS, FLOWERING INTENSITY, AND YIELD

The effect of fall irrigation level in 'Mauritius' and 'Floridian' lyc hee (Litchi chinensis Sonn.) on soil and plant water status, flowering intensity, and yield the following year was studied in a field during 2 consecutive years. At the end of the second vegetative flush after harvest (1 Oct. 1994 and 10 Oct. 1995), four irrigation treatments wer e initiated: 0.5, 0.25, 0.125, and 0 Class A pan evaporation coefficie nts designated 100%, 50%, 25%, and 0%. The three lower irrigation leve ls effectively stopped shoot growth, suggesting the 50% treatment to b e the threshold for shoot growth cessation in both years. For both yea rs, flowering intensity and yield in the 100% treatment were lower tha n those following the other three treatments. Soil and plant water-str ess indicators responded to the water-stress irrigation treatments. Ho wever soil water potential values were highly variable relative to pla nt water potentials. Stem water potential differed more markedly betwe en treatments than leaf water potential. Midday stem mater potential a ppeared to be the best water-stress indicator for irrigation control. Midday stem water potential in both years was correlated with midday v apor-pressure deficit, suggesting that the threshold for irrigation co ntrol should take into account evaporative demand.