Canadian Journal of Pure & Applied Sciences

Abstract: The persistence of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and its effect on microbial population in southern guinea savannah soil was studied using spectrophotometry. The treatments applied were 2.2, 3 and 3.75 L/ha atrazine.The initial soil sample was observed to have higher and significantly different bacterial population (21.30 and 21.63 Cfug-1) than soil from all the rates of atrazine for the two years. Fungal populations were highest (3.7 Cfug-1) in the initial soil samples compared with the rates of atrazine and throughout the duration of the sampling for both seasons. Bacterial population increased from the fourth to the sixth week of sampling and the highest rate of atrazine had the highest bacterial colony for the three consecutive samples.There was steady increase in fungal populations from two to six weeks after atrazine application during the two years.The rate of disappearance of atrazine within the first 28 days was higher (1.33, 1.05 and 0.66 mg/kg for 2.2, 3.0, and 3.75 L/ha respectively) than the second 28 days (1.16, 0.91, and 1.47 mg/kg for 2.2, 3.0, and 3.75 L/ha respectively). The last 28 days recorded the highest rates 2.26, 1.81 and 1.53 mg/kg for 2.2, 3.0, and 3.75 L/ha respectively. The disappearance time for 50% atrazine (DT50 or half-life) irrespective of the rate applied was less than 50 days.Atrazine was observed to be moderately persistent in this zone irrespective of the rates and microbial population increased as the quantity of atrazine residue in the soil decreased considering the duration of the experiment