Soil Chemistry

• Bedrock - the lithified rock that lies under loose softer material called regolith within the surface of the Earth's crust or other terrestrial planets.
• Cation Exchange - the exchange of cations from the surface of a soil colloid to another material.
• Cation exchange capacity - the capacity of soil to adsorb and exchange cations. It is defined as directly proportional to the surface area and the surface charge of the clay.
• Clay - is made of tiny or fine particles with a diameter less than 0.002 millimeters.
• Drainage - refers to the frequency and duration of periods of saturation or partial saturation.
• Humus - the organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms.
• Infiltration - the downward entry of water into the immediate surface of the soil and is influenced by texture, structure, bulk density, and the type and connectivity of macropores.
• Loam - a fertile soil of clay and sand containing humus.
• Permeability - the state or quality of a material or membrane that causes it to allow liquids or gases to pass through it.
• Porosity a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%
• Sand - is made of large or coarse particles with diameters ranging from 0.05 to 2.00 millimeters.
• Saprolite - a chemically weathered rock. Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface. In most outcrops its color comes from ferric compounds.
• Silt - is made of medium-sized particles with a diameter of 0.002 to 0.05 millimeters.
• Subsoil - the layer of soil under the topsoil on the surface of the ground.
• Topsoil - the upper, outermost layer of soil, usually the top 5–10 inches (13–25 cm). It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.
• Weathering - the mechanical breakdown of rock and the associated chemical alteration of minerals that occurs at the Earth's surface.
• Soil - is an important material in sustaining life on our planet. It is a very special mix of inorganic and organic material in form of colloids, water and different gases, and decomposed plant and animal material, all in a variable but balanced proportions (Bear, 1964).
• The largest component of soil is the mineral portion.
• Soils mineral have two types, the primary minerals and secondary minerals.
• Primary minerals - are those soil materials that are the same to the parent material from which they formed, such as those found in sand and silt.
• secondary minerals - are result from the weathering of the primary minerals, which releases important ions and form more stable mineral forms such as silicate clay
• Primary minerals - are formed at high temperature and pressure under reducing condition without free oxygen.
• secondary minerals - are normally found in the clay fraction of the soil
• Water - is the second basic component of soil. It is important for transporting nutrients to growing plants, soil organisms and facilitating chemical decomposition.
• Organic matter - is the next basic component that is found in soils at level of approximately 1% to 5%.
• Soil organic matter - is any material produced originally by living organisms that is returned to the soil and goes through the decomposition process.
• Air - is the next basic component of soil because air can occupy the same space as water. Oxygen is essential for root and microbe respiration which helps support plant growth, carbon dioxide and nitrogen are also important for belowground plant function
• Microorganism - are very small forms of life that can sometimes live as single cells.
• soil texture - is depends on the balance of sand, silt, and clay in soil. Texture is significant since it will affect the soil’s water holding capacity, porosity and aeration, hydraulic conductivity, compatibility, resistance to root penetration, nutrient-holding capacity and resistance to acidification.
• Soil color - does not affect the behavior and use of soil; however, it can indicate the composition of the soil and give clues to the conditions that the soil is subjected to.
• Soil structure - the prior soil particles bond together into larger sized aggregates that are separated by surface of weakness.
• soil horizon - might be slightly or very much different from the other layer existing above or below it. Each horizon also tells a story about the makeup, age, texture and other characteristics of that layer.
• Soil horizon - The layers are divided as top-soil layer, sub-soil layer, and the bed rock layers.
• most of the soils have four or five major horizons. These are designated as O, A, B, C, E and R.
• O-Horizon (humus +litter layer): is very common in many surfaces with lots of vegetative cover. It is the layer made up of organic materials such as dead leaves and surface organisms, twigs and fallen trees.
• A-Horizon (top-soil + root zone): may be seen in the absence of the O horizon, usually known as the top soil. It is the top layer soils for many grasslands and agricultural lands. Typically, this horizon is made of sand, silt and clay with high amounts of organic matter. This layer is most vulnerable to wind and water erosion and it is also known as the root zone
• E horizon: is usually lighter in color, often occurring below O and A horizons. It is often rich in nutrients that are leached from A and O horizons. It has a lower clay content and common in forested lands or areas with high quality O and A horizons
• B-Horizon (Mineral Dominated Zone): This horizon is formed below the O, A and E horizons and may contain high concentrations of silicate clay, iron, aluminum and carbonates. It is also called the illuviation zone because of the accumulation of minerals and in this layer where roots of big trees exist
• C-Horizon (Saprolite layer): C horizon are mineral layers which are not bedrock and are little affected by pedogenic processes and lack properties of O, A, E or B horizons. The C horizon lacks all the properties of the layers above it. It is mainly made up of broken bedrock and no organic material
• R-Horizon: is bedrock horizon. It contains materials that are compacted and cemented by the weight of the overlying horizons. It is the hard layer of unweathered parent material and all kinds are rock types exist as basement