EFFECTS OF SOME INSECTICIDES ON MICROBIAL ACTIVITIES IN SANDY SOIL

Laboratory tests were conducted with 14 insecticides applied to a sand y loam to determine whether these materials caused any effects on micr obial activities related to soil fertility. The ammonification of soil native organic nitrogen was not inhibited by any of the insecticide t reatments. Some insecticides showed an effect on nitrification during the second week of incubation which subsequently recovered to levels s imilar to those obtained in the controls. There was a significant effe ct on denitrification in a number of treated samples. However, recover y of denitrifying capacity was rapid. This recovery indicated that the indigenous soil microorganisms can tolerate the chemicals used for co ntrol of insect pests. No significant inhibition of sulfur oxidation w as observed. Results indicated that the insecticide treatments at the level tested were not drastic enough to be considered deleterious to s oil microbial activities important to soil fertility.