Influence of Agricultural Land Use Management on Soil Particle Size Distribution and Nutrient Adsorption in Western Kenya.

Abstract

In Kenya, less than 10% of the land is arable, out of which 30% suffers severe soil degradation. This study investigates impact of various agricultural land use management practices (on the concentration and distribution of essential nutrients in different soil particle size fractions (SPSF) within Oroba Valley, Nandi County. Two agricultural plots were selected: Plot 1 (non-terraced) and Plot 2 (terraced cultivation), with topsoil (0-20 cm) sampled using a stratified method. Soil particles were separated by sieving (2000-500 µm, 500-100 µm, 100-50 µm, 50-25 µm) and sedimentation (25-10 µm and < 10 µm). Organic matter (OM), soil pH, and nutrient concentrations were quantified using loss on ignition (LOI), a pH meter in CaCl2, and ICP-QQQ analysis, respectively. Median soil pH was 5.6 for Plot 1 and 5.9 for Plot 2, with OM concentrated at 40% in smaller particles (< 25 µm) and 24% in larger particles (100-2000 µm). Nutrients such as I, Se, Zn, Mg, P, Al, Mn, Fe, Co, Mo, and Cu were concentrated in SPSF of < 10 µm, while Na, K, and Ca were concentrated in medium particle sizes (25 µm-100 µm). Terraced plot (Plot 2) experience greater nutrient loss down the slope compared to Plot 1, that showed nutrient accumulation at lower elevations. Principal component analysis (PCA) revealed that soil pH did not significantly influence element adsorption within SPSFs. Differences in land use management between plots directly impacted nutrient distribution. Optimising agricultural land management can improve soil health, contributing to attaining the United Nations sustainable development goals 1, 2, 6, and 8.

Supplementary information: The online version contains supplementary material available at 10.1007/s42250-025-01202-6.