EFFECT OF STAND DENSITY ON GROWTH AND YIELD OF 12-YEAR OLD AZADIRACHTA INDICA A. Juss. var. siamensis VALETON PLANTATION

Abstract

The study on effect of stand density on growth and yield of 11 and 12-year old Azadirachta indica A. Juss. var. siamensis Valeton plantations was carried out at Ratchaburi Forest Experiment Station , Ratchaburi Province. The experimental stands were planted with eight different planting density: 40,000, 17,778, 10,000, 4,445, 2,500, 625, 278 and 157 trees/ha. The data collection was done on October in 1994 and 1995. Enumeration of all trees was done and the diameter at ground level (Do), diameter at breast height (D) of each tree in each stand density were measured. Three sample trees representing the mean tree of each D class of the whole planting density were cut down from the buffer zone of the experimental plot following the stratified clip technique method and their roots digged up. Biomass of each part per tree and yield of each part per unit area were estimated for 2 age classes. The study revealed that growth in forms of mean diameter at ground level and at breast height tended to increase as tree density decreased in both 2 age classes. Maximum and minimum sizes of trees were found in 157 trees/ha and 40,000 trees/ha plots respectively. The survival percentages of trees also showed the similar trend. Biomass of each part per tree tended to decrease with the rising of stand density. Maximum and minimum biomass per tree were found in 157 trees/ha and 40,000 trees/ha plots respectively. Yield of each part per unit area were positively increased with the increasing of stand density up to the maximum in 10,000 trees/ha stand density and beyond this they tended to decrease as stand density increased.