SPECIES AND SEED SOURCES TRIALS OF ACACIAS

Abstract

Eleven species of Acacia were introduced from 22 seed sources, mostly from Australia, to be planted at Saithong Forest Tree Experimental Station, Bang Saphan district of Prachuap Khiri Khan Province. The study site was 50 m above mean sea level, 1,500 mm mean annual rainfall, 20° C minimum temperature, and 34° C maximum temperature. Soil property could be classified as moderate in terms of fertility having pH 4.9 Randomized block design was employed having 22 treatments and 3 blocks. There were 25 sample trees in each plot of 2x2 m spacings. The 3-year-old results revealed that A. crassicarpa and A. auriculiformis showed the best performances, while A. melanoxylon and A. polystachya were the worst ones, A. crassicarpa and A. auriculiformis introduced from Papua New Guinea grew faster than those from Australia. The top-five seed sources were No. 13683 (A. crassicarpa from PNG, 14.69 m height and 14.94 cm dbh) followed by No. 13680, 13681, 13684, and 13686. The last two sources were A. auriculiformis. Seed source No. 14176 (A. melanoxylon from Queensland) which was the worst seed source had only 3.86 m height and 2.20 cm dbh. These height and dbh were only 1/3.8 and 1/6.8 of A. crassicarpa, respectively. Another finding of interest was that A. mangium grew much slower than A. crassicarpa and A. auriculiformis. Based on this 3-year experiment, A. crassicarpa and A. auriculiformis from Papua New Guinea were recommended to be planted at Prachuap Khiri Khan. A. melanoxylon, A. polystachya, and A. aulacocarpa from Queensland must be avoided