Influence of Crop Farming on Soil Chemical Properties and Sustainable Watershed Management in the Tungu–Nithi Sub-Catchment, Kenya
Abstract
This study assessed the influence of crop farming on soil chemical properties within the Tungu–Nithi sub-catchment, Tharaka Nithi County, Kenya. Soil samples were collected from twelve sites, comprising six crop (T1–T6) and six non-crop (N1–N6) locations across the upper, middle, and lower sections of the watershed. The parameters analyzed included soil pH, nitrate, phosphate, and sulfate. In addition, farmer perceptions regarding the influence of agricultural practices on soil quality were evaluated using a structured Likert-scale questionnaire. Data were analyzed using descriptive statistics and the non-parametric Kruskal–Wallis test. The results revealed significant spatial and land-use variations in soil properties (p < 0.05). Cultivated areas exhibited consistently lower pH values, indicating increased soil acidity associated with the application of ammonium-based fertilizers in tea, maize, and coffee farming. Nitrate concentrations were significantly higher in crop sites across all sections, with peak levels recorded in the middle section. Similarly, phosphate and sulphate concentrations were elevated in cultivated soils, particularly in the middle and lower sections, reflecting intensive farming practices, fertilizer inputs, irrigation, and nutrient transport processes. Farmer perception data supported these findings, as the majority of respondents acknowledged that fertilizer use, irrigation, pesticide application, and monocropping influence soil conditions. These findings demonstrate that crop farming significantly alters soil chemical properties within the sub-catchment, highlighting the need for sustainable soil and watershed management strategies to prevent nutrient accumulation and environmental degradation.
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Copyright (c) 2026 Wanja Sarah KIBAARA, Moses Njeru Kathuri, Dickson Kinoti Kibetu, James Muthomi Riungu
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