Which soil characteristics influence a pesticide's leaching ability?

• A. Soil texture and organic matter
• B. Pesticide color
• C. Time of day
• D. Plant type

Answer: (A)

Leaching is about how water moves through soil and how much pesticide sticks to soil particles. The most influential soil characteristics are soil texture and organic matter because they determine both how fast water travels downward and how strongly the pesticide can be held in the soil.

Soil texture describes the sizes of the mineral particles—sand, silt, and clay. Coarse-textured soils with more sand have bigger pores, so water drains quickly and dissolved pesticides can move downward more readily. Finer soils with more clay and silt drain more slowly, but they also have more surface area and can adsorb more pesticide, which reduces its movement toward the groundwater.

Organic matter adds even more surface area and binding sites. Pesticides that adhere to organic matter are retained in the upper soil layers, decreasing the likelihood that they will leach downward with percolating water.

Because leaching depends on how water and pesticide interact with soil, texture and organic matter are the key characteristics. Pesticide color, time of day, or plant type don’t directly determine how readily a pesticide moves through soil to deeper layers.