Analysis of Physicochemical Properties, Plant Nutrients, and Pesticide Residues in Soil Obtained from Pwani University Farm in Kilifi County, Kenya

Abstract

Soil health is central to sustainable agricultural productivity, yet intensive farming practices can introduce physicochemical imbalances and pesticide contamination that threaten environmental quality and food safety. This study evaluated the soil's physicochemical properties, plant nutrient levels, and pesticide residues across thirteen agricultural sites to assess the soil's quality and contamination status. Soil samples were analyzed for pH, electrical conductivity, total dissolved solids, moisture content, organic matter, organic carbon, and plant nutrients using standard protocols. Pesticide residues were quantified using LC-MS/MS. Statistical analyses were conducted using Microsoft Excel and R software, applying one way ANOVA to test for significant differences among sites and Principal Component Analysis to identify dominant factors influencing soil variability. Soil pH ranged from 6.87 to 7.96, while EC ranged from 254.91-1737.50µS/cm. Moisture content was not statistically significant (p > 0.05). Significant spatial variation (p < 0.05) was observed for most other parameters, with macronutrients concentrations ranging widely (N: 16.20–1608.62 mg/kg; P: 7.92–28.08 mg/kg; K: 141.84–370.20 mg/kg). PCA revealed that the first four components explained 70.9% of the total variance. with soil fertility. Multiple pesticide residues were detected, with diazinon (0.03–486.82 ppb) and chlorfenvinphos occurring at notably high concentrations (4.13–624.86 ppb). Chlorpyrifos (0.104–5.94 ppb) was present at moderate levels. The findings emphasize the need for site-specific management strategies, adoption of integrated pest management, and stronger regulatory frameworks to minimize pesticide risks while optimizing nutrient use. These results provide a scientific basis for sustainable soil management and long-term agricultural productivity.