When a pesticide is applied to a field, certain reactions follow. Foliar-applied pesticides stick to leaves, where they are absorbed. Soil-applied pesticides generally interact first with moisture around and between soil particles, influencing how the chemical ultimately will react in the environment. Thus, a 'soil solution' can be viewed as a chemical staging area for most reactions controlling environmental fate. The convention of 'like dissolves like' holds for pesticide interactions with organic matter in soil.
Pesticides move between organic matter and water in soil.
Also, pesticides may undergo an aging process, over time, whereby the chemical moves deeper into organic matter and becomes unavailable to move back into soil solution. Pesticides that are water soluble tend to remain at the surface of soil organic matter, while those that are insoluble will penetrate to the hydrophobic interior. Sorption to clay mineral particles also occurs but usually is less significant than sorption to organic matter in determining environmental fate, unless the soil has very low organic matter content. If the pH-induced charge is positive, the pesticide can bind to negatively charged soil. If the induced charge is negative, the pesticide may actually be repelled from the negatively charged surfaces of soil solids.