Soil Chemistry
Article by: Garrison Sposito, College of Natural Resources, Department of Plant and Soil Biology, University of California, Berkeley, California.
Content
• Elemental composition
• Minerals
• Ion exchange
• Soil solution
Key Concepts
• Chemical processes, including hydrolysis, ion-exchange,
and hydration, change the chemical composition of soil
(such as ion and mineral content) over time.
• Soils can be divided into organic soils and mineral soils.
The main elements of organic soils are carbon, oxygen,
hydrogen, nitrogen, phosphorus, and sulfur, whereas the
main elements of mineral soils are silicon, aluminum,
and iron.
• Soils' cation- and anion-exchange capacities describe the
degree to which soils can adsorb and exchange cations or
anions, respectively.
• Mineral stress occurs when soil suffers from nutritional
deficiencies and toxicities, which limit its plant growth
potential.
• On a large scale, the nutrient content of soils impacts both
plant and animal production; deficiencies in certain miner-
als can impact plant growth and development as well as
animal health.
Access to this content is available to Ward's World readers for free from McGraw Hill's
AccessScience, an award-winning, digital STEM resource containing exclusive articles written by
expert scientists and engineers; biographies of well-known scientific figures; science news, videos,
and animations; and much, much more.
Instructors can use AccessScience to guide students on their research project journeys, to help
students understand scientific concepts, to support distance learning efforts, in flipped classroom
approaches, and in countless other ways.
Ward's World and AccessScience have partnered to offer educators a no-obligation,
free trial subscription to AccessScience. Request your free trial today to discover how
valuable AccessScience can be for you and your students! Get your free trial now.
The study of the composition and chemical properties of
soil. Soil chemistry involves the detailed investigation of the
nature of the solid matter from which soil is constituted and
of the chemical processes that occur as a result of the action
of hydrological, geological, and biological agents on the solid
matter. Because of the broad diversity among soil components
and the complexity of soil chemical processes, the application
of concepts and methods employed in the chemistry of aque-
ous solutions, of amorphous and crystalline solids, and of solid
surfaces
is required. In addition, soil chemistry controls the
availability of plant nutrients within the soil and thus influenc-
es plant growth (Fig. 1), yield, and nutritional value for human
or animal consumption.
Elemental composition
The elemental composition of soil varies over a wide range,
permitting only a few general statements to be made. Those
soils that contain less than 12–20% organic carbon are termed
mineral. (The exact percentage to consider in a specific case
depends on drainage characteristics and the clay content of the
soil.) All other soils are termed organic. Carbon, oxygen,
hydrogen, nitrogen, phosphorus, and sulfur are the most
important constituents of organic soils and of soil organic
+
ward
'
s
science
Fig. 1: Proper soil chemistry helps a green seedling to sprout out from the soil. Soil
chemistry controls the availability of plant nutrients within the soil and thus influences
plant growth. (Credit: amenic181/Shutterstock)
