Illuviation : The process of depositing soil material removed from one horizon in the soil to an-

other, usually from an upper to a lower horizon in the soil profile. Illuviated substances include

silicate clay, hydrous oxides of iron and aluminum, and organic matter.

Leaching : The removal from the soil of materials in solution.

Loam : Soil material that contains 7 to 27% clay, 28 to 50% silt, and less than 52% sand.

Metabolism : The total of all the chemical reactions that occur within a living organism.

Micronutrient : A chemical element necessary only in small amounts (usually less than 1 part per

million in the plant) for the growth of plants and the health of animals. Examples of these elements

are boron, molybdenum, copper, iron, manganese, and zinc. “Micro” refers to the amount, not the

essentiality of the element to the organism.

Mineral :Ausually inorganic substance which occurs naturally, and typically has a crystalline struc-ture, whose characteristics of hardness, lustre, color, cleavage, fracture and relative density can be

used to identify it. Each mineral has a characteristic mineral composition. Rocks are composed of

minerals.

Mineralization : The conversion of an element from an organic form to an inorganic state as a result of microbial decomposition.

Nutrient : An element or compound essential as a raw material for organism growth and develop-

ment.

Particle-size Analysis: The determination of the various amounts of the different separates in a soil sample, usually by sedimentation, sieving, micrometry, or combinations of these methods.

Pollutant : A by-product of human activities which enters or becomes concentrated in the environment, where it may cause injury to humans or desirable species. In addition to chemical substances,the term also embraces noise, vibration and alterations to the ambient temperature.

pore space: The total space not occupied by soil particles in a bulk volume of soil.

Precipitate : A suspension of small solid particles produced in a liquid by chemical reaction.

Precipitation : The deposition of hail, mist, rain, sleet, or snow onto the earth.

Reduction : A reaction in which atoms or molecules either lose oxygen or gain hydrogen or elec-

trons.

Sand  (textural class): Soil material that contains 85% or more sand; the percentage of silt plus 1.5 times the percentage of clay does not exceed 15.

Sandy Clay: Soil material that contains 35% or more clay and 45% or more sand.