Abstract:
Pesticides are chemical compounds used to kill pests such as insects, rodents, fungi, and invasive plants. As about 10 to 15% of the production of the world's major crops, such as rice, wheat, maize, and potato, is lost each year owing to pest-induced plant diseases. However, most of these agriculture pesticides have a serious and longtime effects on useful soil microbial flora. In this study, isolation and identification of soil bacteria followed by the determination of the effect of commonly used agriculture pesticides on garden soil bacteria were investigated. Isolation and identification using morphological and biochemical characterizations were carried. Four pesticides: Cypermethrin, Lambda-cyhalothrin, Glyphosate ammonium, and Paraquat dichloride
were selected and used for soil treatment. Isolation and determination of the colony forming units at 0 to 9 days at different concentrations of the pesticides were investigated. The colony forming unit at 24 hours of incubation ranged from 54×101 - 11×105 cfu/mL and 44×101 -9×105 cfu/mL for the garden maize and eggplant soil samples respectively. Bacillus spp. Klebsiella spp. and Pseudomonas spp. were the predominant bacteria. For the pesticide’s application, the colony forming units at the end of 9 days of incubations ranged from 50×103
– 400×103, 68×103 – 320×103 , 55×103 – 120×103 , 30×103 – 260×103 for glyphosate, lambda-cyhalothrin, cypermethrin and paraquat dichloride respectively. For glyphosate, the highest was recorded at day 3 (1.0 g/ha) and the lowest at day 9 (2.0 g/ha). For Lambda-cyhalothrin, the highest was recorded at day 3 (400
ml/ha) and the lowest at day 9 (800 ml/ha). For cypermethrin the highest was recorded at day 3 (500 ml/ha) and the lowest at day 9 (1000 ml/ha). For Paraquat dichloride, the highest was recorded at day 3 (1.5 ml/ha) and the lowest at day 9 (3.0 ml/ha). This study showed that the investigated pesticides negatively affect microbial counts and activity in soil, which confirmed previously reported environmental concerns.
