Soils with a loose structure or soils with hollow channels such as dried root channels or animal or worm tunnels, will also allow for increased flow of water through the soil profile. Soils that permit rapid flow of water through the soil profile present a higher potential for ground water contamination than less permeable soils. Sandy soils with their coarse textures and low water-holding capacity will allow for greater infiltration than finer, heavier clay soils. Organic Matter Organic matter is another soil property that influences the fate of pesticides in soil. Soils high in organic matter tend to hold more water, which may make less water available for leaching.
Organic matter is the single most important factor affecting adsorption of pesticides in soils.
Organic matter content of soils may be increased by the addition of manure and incorporation of crop residues. If soils are already wet or saturated before rainfall or irrigation, excess moisture will runoff. Soil moisture also influences pesticide breakdown. Rainfall Intense or sustained periods of high rainfall may cause large amounts of water to move through the soil, especially where little run-off occurs. Avoid using pesticides prior to heavy rain or irrigation.