Sustainable Soil Management
Glossary
I
IGNEOUS ROCK. Rock formed from the cooling and solidification of magma that has not been changed appreciably since its formation.
ILLUVIATION. The deposition of materials such as clays, organic matter, iron, or aluminum into a horizon; generally, the materials come from an upper horizon in the soil body.
IMOBILE NUTRIENT. A plant nutrient that moves slowly in the soil or plant.
IMMOBILIZATION. The conversion of an element from the inorganic to the organic form in microbial tissues, resulting in that element not being readily available to other organisms or plants.
IMPERMEABLE LAYER. Soil layers, either natural or man-made, that resist penetration by fluids or roots.
INCEPTISOLS. An order in Soil Taxonomy. Soils that are usually moist with pedogenic horizons of alteration of parent materials but not of illuviation. Generally, the direction of soil development is not yet evident from the marks left by various soil-forming processes or the marks are too weak to classify in another order.
INFILTRATION. Entry of water from precipitation, irrigation, or runoff into the soil profile.
INJECTION. Placing something below the surface of soil by mechanical means.
INORGANIC NITROGEN. Mineral forms of nitrogen.
INORGANIC PHOSPHORUS. A salt of phosphoric acid or any of its anions, usually orthophosphate or polyphosphate.
IRRIGATION. Application of water to supplement natural rainfall.
