THE EFFECT OF SPIRAL GIRDLING ON THE FRUIT-SETTING AND DEVELOPMENT OF YOUNG LITCHI TREES

Trunk spiral girdling was carried out on six years old litchi (Litchi chinensis Sonn. ‘Nuomici’ and ‘Guiwei’) trees which poorly fruiting during the early flower bud differentiation phase (about early December). A 1.2 to 1.8 spiral circle with a width of 0.2 to 0.4 cm and a spiral angel of 16-19 degrees was extended into the xylem of the trunk or branch. The wound was almost healed at harvesting time. Compared with the control (no girdling), the ratio of fruit-setting plants was 55.3, 64, 74.7, 78, 74 and 73.3% higher in cultivar ‘Nuomici’, and 58, 62.7, 68.7, 73.3, 70 and 65.4% higher in cultivar ‘Guiwei’ in 2000, 2001, 2002, 2003, 2004 and 2005, respectively. Yield per plant was 2.5, 4.2, 6.5, 9.2, 13.5 and 16.5 kg higher in cultivar ‘Nuomici’, and 2.4, 3.8, 5.5, 8.9, 13.9 and 14.8 kg higher in cultivar ‘Guiwei’, respectively. The plants with spiral girdling fruited 6 years early than control. Total sugar concentration in fruit of plant with spiral girdling was 3.5 and 2.1% higher than those in control, while total acid concentration was 0.7 and 0.4% lower than those in control in cultivars ‘Nuomici’ and ‘Guiwei’, respectively.