Lecture 3

Clay Minerals• Clay minerals and organic matter are the primary factorscontributing to the chemical reactions in soils; high surface areasand electrical charge characteristics are the reason soils arechemically dynamic.• Colloidal mineral and organic particles have extremely high chargeto-arearatios that make them important in processes that includewater retention, cation and anion exchange, sorption of inorganicand organic compounds, pH buffering as well as creating numerousother dynamic physical, chemical, and biological soil attributes thatare essential to the fertility, structure, and quality of soilenvironments.• In addition, factors associated with acidity, salinity, and sodicity playsignificant roles in soil chemistry, and have been labeled “mastervariables” along with a soil’s redox (e.g., oxidation—reduction)status. Soil chemical properties have a profound influence onagricultural production, soil quality and health, and on the overallsustainability of the soil ecosystem.