Long-term reclamation outcomes in Indonesian tidal lowlands: soil fertility, soil quality, and implications for Soil Security

Evaluating the long-term outcomes of reclamation requires assessment not only of soil fertility but also of soil functioning within a Soil Security perspective. This study assessed soil fertility status and the Soil Quality Index (SQI) in reclaimed tidal lowlands after more than 30 years of cultivation in Typology A and Typology B areas of Banyuasin Regency, South Sumatra, Indonesia. Soil chemical properties were analyzed and compared using Welch’s t-test or Mann–Whitney U test according to data distribution, while effect sizes were quantified using Cohen’s d and rank-biserial correlation. Both typologies exhibited strongly acidic conditions (pH 4.0–5.0), moderate cation exchange capacity (14–25 cmol kg⁻¹), low base saturation (11–43%), low available K, moderate total N, relatively high organic C (1.3–13.0%), and loam to clay loam textures. Significant differences between typologies were observed for cation exchange capacity, base saturation, and soil pH, whereas available P, available K, total N, and organic C did not differ significantly. Soil fertility in both typologies remained constrained primarily by persistent acidity and low base saturation. SQI values were 0.74 for Typology A and 0.70 for Typology B, indicating moderate soil quality in both typologies. Within the Soil Security framework, differences between typologies were mainly related to the capacity dimension, particularly nutrient retention and buffering functions, whereas SQI reflected the current soil condition under long-term management. The persistence of chemical limitations indicates that reclaimed tidal lowlands remain dependent on liming, nutrient replenishment, water management, and organic matter maintenance to sustain agricultural productivity and long-term soil security.