Effects of chemical insecticides on the properties of soil using maize as a test crop

A pot experiment was conducted to evaluate the effect of commonly used chemical insecticides on some soil properties using maize as a test crop. The insecticides include Dichlorvos, karate, and phoskill at the rates of 0 l/ha (R1 control), 1.2l/ha (R2), 0.8l/ha (R3) and 0.4l/ha (R4). Upland sandy soil was used which was treated with the chemicals. The experiment was laid in a completely randomized design replicated 3 times. Plant hight, and leaf number were measured weakly starting from 2 weeks after emergence. At the end of the experiment (8 weeks), the plants were harvested in two portions (shoot and root) which were oven dried at 65 C for 24 hours and the dry matter determined. Soil properties such as pH, exchangeable bases, organic carbon and total nitrogen were determined. The result on plant height and dry matter shows no significant effect (P > 0.05) of insecticides. Similar trend was observed in most soil properties, but comparing the mean values, control shows better performance .the result on plant leaf number shows a significant effect of chemical insecticides. The general non significant effect of the chemical insecticides on plant growth parameters, dry matter and soil properties have been attributed to the sandy nature of the soil which has poor adsorption capacity and the due to the little time the chemicals are exposed to the soil.