Effect of Chemical Fertilizer on Growth and Soil improvement of Acacia mangium in Nampong Sandy Soil   Seri Chaturangkakul Somnuk Sritongchim and Yuwadee Buttrama   ABSTRACT         Effect of chemical fertilizer (15-15-15) on growth Soil improvement of Acacia mangium in Nampong sandy soil was conducted at Roi - Et Land development Station since 1987 to 1995. The objective of this study were : 1) to study responds of Acacia mangium to different rates of chemical fertilizer (15-15-15) and 2) to study of ability of Acacia mangium to be improved soil fertility of Nampong soil . The experiment design was in RCB arrangent with replicated 3 times the treatments were used therefore :- T1 = chemical fertilizer 500 gram/plant one time after year of planting T2 = chemical fertilizer 250 gram/plant the same as T1 T3 = chemical fertilizer 125 gram/plant the same as T1 T4 = chemical fertilizer 60 gram/plant the same as T1 T5 = chemical fertilizer 500 gram/plant every year T6 = chemical fertilizer 250 gram/plant every year T7 = chemical fertilizer 125 gram/plant every year T8 = chemical fertilizer 60 gram/plant every year The resulted revealed that there was no growth difference of Acacia Mangium after 3 years of planting. But when Acacia mangium has 6 years there was evidently growth difference of plants. Plant applied at the rate of 500 gram/plant/yr showed highest girth and height (90.00 cm and 6.77 meters) respectively. Also plant applied with chemical fertilizer at the rate of 500 and 250 grams gave the highest biomass of 23.75 and 19.82 ton/rai. In case of Soil fertility, there was no significant difference of soil before and after of experiment.         Keyword : Chemical Fertilizer, Acacia mangium