AN INVESTIGATION OF AGROCHEMICAL TRANSPORT MECHANISMS IN SOME CULTIVATED SOILS IN GHANA

ABSTRACT The study basically examined the movement of agrochemical compounds in soil. Four different soil samples made up of three sandy loams and a sandy clay were used in the study. Potassium chloride solution and chlorpyrifos were used as infiltration solutions in a horizontal infiltration study under laboratory conditions. At the end of each experiment, the infiltration column was sectioned and the moisture content as well as the solution concentration of the agrochemical compound (Cl- , K+ , and chlorpyrifos) contents determined. The water content, Cl- , K+ and chlorpyrifos contents profiles preserved similarity with regards to the variable . Moisture diffusivity and dispersion coefficients were therefore considered to be dependent on water content only. The moisture diffusivity function and the dispersion coefficients of the solutes were derived using the θ(λ) and c(λ) data together with the Continuous System Modeling Program (CSMP) computer program. The moisture diffusivity values obtained showed that the sandy loams due to their large pore sizes permitted higher infiltration of water than the sandy clay. With the exception of the Xanthic Ferrasol and Ferric Lixisol, which are sandy loam, the chloride profiles moved ahead of the profiles of water and the other solutes. The chloride concentration front measured in the Ferrasol and Lixisol lagged behind that of the water, thus suggesting chloride mobility was retarded during the infiltration experiment. Differences in the notional planes of chloride and water used as influent solutions in the infiltration experiments also suggests the existence of immobile water content in the sandy clay and one of the sandy loams. Estimation of the dispersion coefficient of chloride in the two