Pesticide Applicator Training: General Standards SP39-W Practice Test

Leaching happens when water moves downward through soil carrying dissolved pesticides. The likelihood of this movement is strongly influenced by soil texture and drainage. Sandy soils drain quickly because their coarse particles create large pore spaces and little surface area to hold pesticides, so water and any dissolved chemicals pass through rapidly. That makes leaching more likely in sandy soils. In contrast, clay soils have small pores and high adsorption, so they hold onto chemicals longer and slow percolation, reducing leaching risk. Lots of rainfall increases the amount of water moving through the soil, which can promote leaching, but the soil type in this list is the clearest predictor, making sandy soils the best answer. Deep groundwater is about how far water must travel to reach groundwater, not how readily leaching occurs in the soil itself.