This decreases the threat of contamination from leaching. However, extremely low permeability can increase the chance of pesticide runoff. Clay soils also can contain more organic matter. Although organic matter generally makes up less than five percent of most soils, it improves physical characteristics of the soil such as structure and permeability. Good soil structure and permeability reduce the potential for soil erosion and limit pesticide runoff.
Organic matter is also the most chemically active part of the soil.
Its chemical reactivity and large surface area make organic matter an ideal environment for pesticide sorption. Depending on the pesticide and targeted pests, this high sorption capacity can be either beneficial or harmful. Fortunately, most agricultural fields are maintained at a pH level acceptable for pesticide application. Geology and surrounding water sources Characteristics of geological layers beneath soils can vary. An understanding of these formations is another key element in selecting the proper pesticide.