ACID SULFATE SOILS ARE MINERAL SOIL THAT CONTAINS FeSAND IS USUALLY FOUND IN TIDAL SWAMP AREAS. THE PROBLEMS FREQUENTLY ENCOUNTERED IN ACIDIC SULFATE SOILS INCLUDE HIGH ACIDITY, LOW AVAILABILITY OF P, AND HIGH P FIXATION BY Al AND Fe, RESULTING IN LOW CROP YIELDS. HIGH ACIDITY TRIGGERS THE DISSOLUTION OF TOXIC ELEMENTS AND NUTRIENT DEFICIENCIES, MAKING THE SOIL UNPRODUCTIVE. ONE EFFORT TO INCREASE SOIL FERTILITY IS TO ADD AMELIORANTS. THIS RESEARCH AIMED TO DETERMINE THE EFFECT OF PROVIDING A COMPOSITION OF RICE STRAW COMPOSTAND WATER HYACINTH (Eichhornia crassipes) COMPOST IN INCREASING pH AND NUTRIENT AVAILABILITY IN ACID SULFATE SOIL. THIS RESEARCH USED A SINGLE FACTOR IN A COMPLETE RANDOMIZED DESIGNCONSISTING OF SIX TREATMENTS AND REPEATED FOUR TIMES TO OBTAIN 24 EXPERIMENTAL UNITS, INCLUDING K0 = CONTROL, K1 = 100%RICE STRAW COMPOST(5 t Ha^-1), K2 = 100% WATER HYACINTH COMPOST (5 t Ha^-1), K3 = 50% RICE STRAW COMPOST (2.5 t Ha^-1) + 50% WATER HYACINTH (2.5 t Ha^-1), K4 = 75% RICE STRAW COMPOST (3.75 t Ha^-1) + 25% WATER HYACINTH COMPOST (1.25 t Ha^-1), K5 = 25% RICE STRAW COMPOST (1.25 t Ha^-1) + 75% WATER HYACINTH COMPOST (3.75 t Ha^-1). THE RESULTS SHOWED THAT THE APPLICATION OF RICE STRAW COMPOST AND WATER HYACINTH COMPOST WAS ABLE TO INCREASE SOIL pH, AVAILABLE-P,AND ABLE TO LOWER SOIL EXCHANGEABLE-Al BUT NOT SIGNIFICANT IN REDUCING SOIL Fe.