Cassava (Manihot esculenta) Leaf Extract: Effects on Soil pH and Microbial Population Dynamics in Greenhouse and Field Conditions

Abstract

Sustainable soil management practices play an important role in maintaining soil quality and enhancing agricultural production. This study evaluated the effects of cassava leaf extract on soil pH and microbial population (bacteria and fungi) under greenhouse and field conditions. A 5×2 factorial design in a Randomised Complete Block Design with three replicates was arranged, consisting of five extract concentrations (0%, 25%, 50%, 75% and 100%) and two environments (greenhouse and field). Data were analysed using SAS version 9.4, and means were separated using Tukey's Honestly Significant Difference (HSD) at p ≤ 0.05. Soil analysis was done after four weeks of extract application. The results indicated that cassava leaf extract had no significant effect on soil pH (p=0.9955) and soil fungi (p=0.0853), whereas the environmental conditions influenced both parameters (P< 0.0001). In contrast, both cassava leaf extract (p = 0.0168) and the environment (p < 0.0001) had significant effects on soil bacteria. The Tukey post hoc test showed no significant differences in individual concentration levels. Fungal and bacterial populations were consistently higher under field conditions than under greenhouse conditions. The findings suggest that differences in greenhouse and field conditions exert a greater influence on soil chemical and biological processes than the concentration of cassava leaf extract. Therefore, cassava leaf extract had minimal effects on soil pH and microbial population under greenhouse and field conditions. The study recommends evaluating the long-term effects of repeated cassava application under different agroecological conditions using various cassava varieties to better understand its influence on soil health.