The research was to evaluate the presence of sulfuric horizon, sulfidic materials (SM) and soil fertility to plan the proper fertilizer application. Soil morphological characteristics were directly described in the field, and soil samples from original horizons were collected to analyze the physicochemical parameters. The results showed that soil profiles from Tan Tien site were classified as active acid sulfate soil (ASS) with shallow presence of SM at 35-70 cm, and potential ASS with shallow

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... resence of SM at deeper 30-75 cm while profiles from Hoa Tien location were categorized as potential ASS with deep presence of SM. For parameters of soil chemistry, surface soil pHKCl was lower than 4.0. Concentration of Al 3+ and Fe 2+ toxicity was lower than 5.0 meq Al 3+ 100 g -1 and 10 mg kg -1 , respectively. Besides, total nitrogen was evaluated at medium level, and total phosphorus at low threshold, with 0.41 -0.55% and 0.008 -0.058%, respectively. Concentration of available ammonium and soluble phosphorus in top soil layer was 75.5 -186.7 mg NH4 + kg -1 and 38.0 -45.6 mg P kg -1 . However, soil phosphorus fractions of aluminum and ferrous phosphorus possess high concentration (76.0 -188.6 and 18.5 -42.1 mg P kg -1 ) on top soil surface. For soil physical characteristic as soil texture was determined as clay and silty clay. In general, fertility of ASS cultivated pineapple is low based on morphological and physicochemical properties.