Movement of surface-applied phorate and water through unsaturated soil

Abstract

The simultaneous movement of surface-applied phorate and water was studied in laboratory columns containing, initially, moist and dry sandy loam soil. Phorate was applied onto the soil and leached with water under ponded and controlled infiltration conditions. Phorate and water distribution profiles were determined by destructive sampling at two stages: (1) immediately following infiltration and (2) after matching total infiltration, redistribution and evaporation time for two water-application rates. Regardless of the initial soil water content, just after the termination of infiltration, phorate was displaced more efficiently and its concentration peak formed at deeper depth with the slower than with the faster application rate. Following redistribution, this trend was reversed. Phorate movement was also found to be dependent on the initial soil water content. The higher the initial soil water content, the deeper and more complete was the displacement of phorate during infiltration and redistribution.