Emmanuel R. Mwakidoshi, Catherine Muui, Esther M. Muindi, Sagar Maitra, Masina Sairam, Harun I. Gitari, Mahmoud F. Seleiman
Soil acidity remains a critical barrier to sustainable agricultural productivity in humid and sub-humid regions, where high rainfall, intensive cultivation, and limited soil amendment practices accelerate nutrient depletion and aluminum (Al³?) toxicity. Despite the importance of understanding soil acidification mechanisms, little attention has been given to the vertical and spatial variability of exchangeable acidity and its relationship with soil morphological and physicochemical properties. This study aimed to evaluate the profile distribution of exchangeable acidity and related soil morpho-physicochemical characteristics to elucidate the underlying causes of persistent acidity in cultivated agricultural landscapes. The study was undertaken in Molo, Nakuru County, Kenya, where two representative soil profiles were excavated in intensively cultivated acidic soils representing contrasting slope positions within the same agricultural landscape. The results indicated that both profiles exhibited well-developed horizonation with distinct morphological differentiation and moderate to strong structure, consistent with deeply weathered soils under high rainfall. The soils were strongly to extremely acidic (pH 4.3–5.1) throughout the profile, with acidity more pronounced in the surface and subsurface horizons. Exchangeable acidity (H? + Al³?) and Al³? saturation was inversely related to base cation concentration and CEC, whereas organic carbon and total nitrogen declined sharply with depth. The predominance of fine-textured, clay-rich horizons further implied advanced weathering and accumulation of low-activity clays. These findings highlight the need for targeted soil fertility management strategies emphasizing lime application, organic matter enhancement and balanced fertilization to restore cation balance and mitigate acidification. The study provides critical baseline data for designing site-specific soil amelioration and nutrient management interventions in acid-prone agricultural landscapes.