Effect of Chemical and Organic Fertilizer Application to Acacia mangium Willd. Planted at Different Spaces on Tin Mine Tailing Land   Boonnarong Taneerat and Sompong Santanakanit   ABSTRACT         The study on effects of spacing and fertilizer application on growth of Acacia mangium Willd. had been conducted on Mined Spoils Experimental Station, Amphoe Thai Muang Changwat Pangnga during 1987 - 1993. The objective of the study was to determine the optimum spacing and appropriate fertilizer application of Acacia mangium Willd. for reclamation of the land after tin mining. The treatments were arranged in split plot design with 3 replications; main plot was spacing with 3 levels : 1x1 m, 2x2 m and 3x3 m and subplot was fertilizer application with 5 levels: no fertilizer, chemical fertilizer (15-15-15) at 300 gm/pl./yr., chemical fertilizer (15-15-15) at 600 gm/pl./yr., manure 10 kg/pl./3 yrs., and compost 10 kg/pl./3 yrs.       The results showed that survival rate of fertilized trees (72 months old) were slightly difference, but they showed highly significance in comparison to trees without fertilization. Furthermore, wider spacing (lower stand density) had better survival rate than narrower one (higher stand density). In case of tree growth, aboveground biomass and litterfall were found to be no interaction between spacing and fertilizer application. However, spacing 2x2 m together with chemical fertilizer (15-15-15) at 300 gm/pl./yr. was the method recommended, showing an average D.B.H. of 14.94 centimeters, aboveground biomass of 17.05 t/rai and of 74.80 kg/tree, and litterfall of 1.37 t/rai/yr.         Keyword ; Chemical and Organic Fertilizer, Acacia mangium, Tin Mine Tailing Land