Short- term effects of cypermethrin pesticide on nutrient levels and microbial communities in tropical soil of Uganda

Abstract

Cypermethrin is an insecticide widely used by farmers in Uganda to control pests and diseases. This study examined the short-term effects of cypermethrin on soil macronutrients (N, P, K), meso-nutrients (Ca, Mg), and microbial communities (bacteria, fungi, and actinomycetes) in tropical Ugandan soils. Soil samples treated with cypermethrin and control were collected and analysed using standard methods of flame photometry for potassium (K), atomic absorption spectroscopy for calcium and magnesium, Wet-acid oxidation for nitrogen and phosphorus, and standard plate count techniques for microbial populations. The study used a Randomized Complete Block Design (RCBD) to investigate the effects of cypermethrin on soil ecosystem in Uganda. Application of cypermethrin resulted in significant changes to soil nutrient levels and microbial communities. Nitrogen levels were similar in both control and cypermethrin treated soils, while phosphorus concentration increased by 10.5% (from 30.6 to 33.8 cmol/kg) in cypermethrin – treated soils. Across seasons, phosphorus content increased by 61.2% (from 18.1 to 46.6 cmol/kg) and 58.8% (from 19.6 to 47.7 cmol/kg) across blocks. Potassium levels increased marginal 3.7%, whereas calcium concentration remained insignificant. Magnesium content increased substantially by 65.5% across seasons. The microbial community was altered with notable increases in bacteria, fungi and actinomycetes populations in cypermethrin-treated. Analysis of variance (ANOVA) was used to compare means between control and cypermethrin-treated soils.  ANOVA model was used to account for seasonal variations. The results provide insight into cypermethrin’s impact on soil ecosystem balance. It further suggests that cypermethrin usage as insecticide in tropical soils can have beneficial and detrimental impacts on soil fertility.