Kilaza Samson Mwaikono^1,, Hamis Mkinga James²

There is a growing usage of herbicides in agriculture to improve productivity, however, there is limited studies on the effect of herbicides to the soil microbiota and nutrients. This study assessed the effect of glyphosate herbicide on the abundance and activity of soil microbiota on the agricultural soil at Kauzeni village, Morogoro, Tanzania. Two groups of soil samples; 15 from soil with herbicides, and another 15 without herbicide application were assessed. Abundance of bacteria and fungi were determined using culture-based method, while soil organic matter and Nitrogen were determined using muffle furnace and Kjeldahl methods, respectively. Bacterial load in soil with glyphosate was found to be (1.5±0.4) ×10⁵ CFU/mL and without herbicide (2.2±0.4) x10⁵ CFU/mL. The fungi load in soil with herbicides was (1.2±0.5) ×10⁵ CFU/mL and without (1.8 ± 0.5) ×10⁵ CFU/ml. The organic matter in soil with herbicide was (12±7) % and without herbicide (28.3 ± 17) %, while Nitrogen in soil with herbicide was (7.0±3.8) % and without (17±6.6) %. ANOVA revealed significant difference in soil microbiota of soil with and without herbicides, P-value = 0.0002 and P-value = 0.0064 for bacterial and fungi, respectively. Soil organic matter and nitrogen contents were also different, p-value = 0.0023 and p-value = 0.00002 for the organic matter and nitrogen content, respectively. Glyphosate affects the abundance of soil microbiota and hence nutrient levels in the soil. There is a need to study the effect of herbicides to different types of soil and provide guideline of its use for a comprehensive management of the soil.

Glyphosate, Soil, Bacteria, Fungi, Organic matter, Nitrogen, Herbicide, Microbiota