Impact of Drifts Resulting from Pesticide Application on Soil Microorganisms around Waste Receptacles in Port Harcourt City, Nigeria

Abstract

Pesticides are toxic substance used to reduce or kill pests but the deposits on soil environment can remain there for long period of time causing adverse effects on soil microorganisms which are responsible for soil health conditions. This study was carried out to determine the impact of pesticide drifts on soil microorganisms in a waste receptacle around Port Harcourt city. Soil samples were obtained from various depths around waste receptacles with hand auger using standard analytical procedures. Microbial analysis was done according to prescribed standard methods. Characterization and identification of the isolates were based on their cultural, morphological, and cellular characteristics. Results obtained showed that the bacterial isolates were identified as Staphylococus aureus, Bacillus subtilis, Bacillus megaterium, Pseudomonas sp and Micrococcus sp while fungal isolates include Aspergillus niger, Penicillium sp, Fusarium siculi, and Aspergillus fumigatus, Aspergillus nidulas, Microsporium canis and Yeast. The results of the microbial counts revealed that Total Heterotrophic Bacteria (THB) had 2.08 ×109 cfu/g at a depth of 30-45 cm while Total Heterotrophic Fungi (THF) had 6.0×106 cfu/g before application with a mean value of 1.02×109 and 2.8 × 106 cfu/g respectively while after application THB had 4.1 × 108 and 4.6 × 108 cfu/g for 0-15 and 30-45 cm respectively while the THF recorded 1.0 × 106 and 0.6 × 106 cfu/g for 0-15 cm and 30-45 cm respectively. However there was a drastic decrease in the number of microbes in the soils after pesticide application especially at the surface soil depth of 0-15 cm. This shows that the pesticides application affected microbial population by reducing their numbers in the soil and this may in turn affect soil health and physiological status of their habitat. It is therefore recommended that proper surveillance during pesticide application should be considered to avoid drift to non-target organisms and that concentrations of pesticides to be used should be taken into account to avoid reduction in the number of microorganisms in soils because of the vital roles they play in maintaining soil health.