Soil chemistry

Soil chemistry studies the composition, reactions, and transformations of substances in soil. It explains how minerals, organic matter, water, and organisms shape nutrient availability and contaminant behavior.

Cation-exchange capacity: A soil’s capacity to reversibly retain and exchange positively charged ions on charged surfaces. It measures how strongly clay and organic matter can hold nutrient cations.
Soil mineralogy: The study of minerals present in soils and their properties and transformations. Mineral identity determines much of a soil’s surface reactivity and nutrient supply.
Plant nutrient availability: The extent to which essential elements in soil can be acquired by plants. Chemical form, pH, and sorption determine whether nutrients reach roots.
Soil science: The interdisciplinary study of soils as natural bodies, resources, and components of ecosystems. Soil chemistry is one branch of this broader study of soil properties and processes.
Chemical speciation: The identification and quantification of distinct chemical forms of an element or compound in a system. Knowing total concentration alone often cannot predict a soil contaminant’s mobility or toxicity.
Soil pH: A measure of hydrogen-ion activity in soil solution, commonly used to characterize soil acidity or alkalinity. It changes mineral solubility, surface charge, and the chemical forms of nutrients.
Clay minerals: Fine-grained phyllosilicate and related minerals with reactive surfaces and high surface area. Their charged layers and edges provide major sites for ion exchange and adsorption.
Soil fertility: The capacity of soil to supply essential nutrients in forms and amounts that support plant growth. Chemical measurements help diagnose nutrient limitations and guide amendments.
Biogeochemistry: The study of how biological, geological, and chemical processes govern the cycling of elements. It places soil reactions within element cycles across ecosystems.
Soil carbon sequestration: The accumulation and long-term storage of carbon in soil. The chemical and mineral controls on persistent soil carbon remain an active research area.

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