Absorption

In plants, the passing of a compound from one system into another such as water movement from soil into plant roots. In soils, the binding of a chemical into a soil particle.

Acclimation

Physical and physiological processes that prepare plants for temperature extremes.

Acid Injection

In irrigation systems, adding of acidic materials such as sulfur or phosphoric acid to irrigation water with excessive pH, bicarbonate, and carbonate contents. This lowers the pH and converts bicarbonate and carbonate into carbon dioxide and water.

Activated Sludge

Aerated sludge that is subjected to bacterial processes.

Acidity

Acidity of a soil solution from free hydrogen ions measured as pH.

Activity Index

Measurement (index) of the proportion of hot water soluble nitrogen (HWSN) relative to hot water insoluble nitrogen (HWIN) in urea formaldehyde fertilizers.

Adhesion

Molecular attraction and contact between the surfaces of two unlike substances or objects.

Adsorption

Bonding or adhering of ions or compounds to the surface of soil particles or plant parts.

Aerobic

Requiring oxygen or having oxygen present in the environment.

Aggregate

Collected together in tufts, groups, or bunches.

Alkaline Soil

Soil that has a pH above 7.0.

Alkalinity

The capacity of water to neutralize acids. A property imparted by carbonates, bicarbonates, hydroxides, and others.

Amendment

Any material such as sand, sawdust, gypsum, diatomaceous earth, peat, or calcined clay that is added to soil to alter its chemical and/or physical characteristics.

Amino Acids

Nitrogen containing organic acids that are building blocks to form proteins. Amino acids contain one or more amino (-NH2) groups, a carboxyl group (-COOH), and possibly sulfur.

Ammonification

Conversion of amino acids and other nitrogen containing organic compounds into ammonia (NH3) and ammonium ions (NH4+).

Anaerobic

Not requiring oxygen or the absence of oxygen in the environment.

Atomic Weight

Weight of an atom of an element relative to the weight of an atom of carbon (12C), which has been assigned the value of 12.

Available Water

Portion of soil water that can be readily absorbed by plant roots. Often considered to be that water held in the soil against a pressure of -33 kPa to approximately -1,500 kPa (or -15 bars).

Bacteria

Microscopic, single cell, non-green organisms with rigid cell walls that reproduce by cell division. Bacteria are prokaryotes.

Base Saturation

The degree to which the cation exchange capacity’s binding or exchange sites are occupied with cations such as calcium, magnesium, sodium, and potassium as opposed to acid cations such as aluminum and hydrogen is referred to as the base saturation of a soil. Soil pH and fertility generally increase as the percentage base saturation increases.

Biodegradation

Breakdown (digestion) by biological organisms.

Buffering Capacity

The ability of a soil to resist chemical changes. The major buffering system for soils is the cation exchange capacity.

Bulk Density

Measurement of soil compaction expressed as a weight per unit of soil (grams per 100 cc).

Calcined Clay

A granular soil modification amendment consisting of highly fired clay minerals such as montmorillinite and attapulgite clays that are absorbent and stable.

Carbohydrates

Plant food sources including sugars and starches containing carbon with hydrogen and oxygen in a 2 to 1 ratio, as in water (H2O).

Carbon-Nitrogen Ratio

Ratio of organic carbon weight to total nitrogen weight in soil or organic material.

Cation Exchange Capacity

Sum of exchangeable cations a soil can adsorb and retain against leaching and is expressed as centimoles per kg of soil or milliequivalent per 100 grams of soil. Sometimes referred to as the

CEC.

Centrifugal Spreader
Machine that spreads granules as they drop onto a spinning disc or blade beneath the hopper.

Chelate

Cyclic structures of a normally non-soluble metal ion and an organic component that, when held together, become soluble in water.

Chlorosis

Yellowing of normally green plant tissue due to chlorophyll loss.

Colloids

Very small particles that are formed during the weathering process of soils.

Compost

Residues from organic matter and soil piles allowed to undergo biological decomposition.

Crown

A meristematic growing point at or just below the ground where stems and roots join and new shoots emerge.

Cultivation

The disturbance of soil and/or thatch layer without destroying the turfgrass (e.g. aerification, slicing, spiking, etc.).

Denitrification

The biological conversion of nitrate or nitrite to gaseous nitrogen as either N2 or N2O.

Dethatching

Removal of excessive turfgrass thatch and/or mat using stiff rakes or a series of vertically mounted knives or tines.

Diatomaceous Earth

Geological deposit of siliceous skeleton material of diatoms (algae).

Effluent

Partially or completely treated waste water from a treatment plant, reservoir, or basin.

Electrical Conductivity (EC)

A measure of salinity using electrical conductance expressed millimhos per centimeter (mmhos/cm) or decisiemens per meter (dS/m).

Electron

A negatively charged subatomic particle which orbits the atom’s positively charged nucleus, determining the atom’s chemical properties.

Element

A substance composed of only one kind of atom. These combine to compose all materials.

Enzyme

A complex organic agent that enhances cellular reaction rates without being altered in the process.

Exchangeable Sodium Percentage (ESP)

A measure of excessive sodium hazard in the soil as the ratio (as percent) of exchangeable sodium to the remaining exchangeable cations (Ca, Mg, and K).

Fertigation

Fertilizing through irrigation systems.

Fertilizer

Any material, except lime, supplying essential nutrients to plants.

Fertilizer Burn

Plant injury from dehydration due to contact with materials containing salts.

Field Capacity

The percentage of water a soil retains against the action of gravity and typically is that remaining in a soil 2 to 3 days after having been saturated and free drainage has occurred. Estimated at -33 kPa water potential.

Foliar Feeding

Light liquid fertilizer applications to plant foliage.

Ground Water

Subsurface water in the zone of saturation that moves freely, often horizontal.

Heavy Metals

Metals with densities of 5 mg per meter or greater and include Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Pb, and Zn.

Hot Water Insoluble Nitrogen (HWIN)

Insoluble nitrogen fertilizer fraction associated with urea reaction fertilizers that is insoluble in hot water (212 F).

Humate (humin)

Portion of soil organic matter that is insoluble in dilute alkali.

Humic Acid

Portion of humus that is water insoluble and is extracted from soil with dilute alkali and precipitated upon acidification.

Humus

Relatively stable, dark-colored colloidal soil organic matter containing no recognizable plant parts.

Hydraulic Conductivity

Rate of water flow in soil as imposed by a hydraulic head.

Hydrolysis

Splitting of one molecule by addition of water.

Immobilization

Conversion of an element from the inorganic form to the organic form in microbial or plant tissues. Often used to describe the conversion of nitrate or ammonium into organic forms by soil microorganisms.

Infiltration Rate

Downward movement or entry of water into the soil.

Ions

Electrically charged atoms resulting from the loss of electrons (cations) or gain of electrons (anions).

Leaching

Downward movement of soluble materials through a soil.

Lime

Calcium oxide (CaO) and/or a variety of acid neutralizing materials containing Ca, Mg, or both Ca and Mg.

Limestone

Sedimentary rock composing more than half calcium carbonate (CaCO3).

Liquid Fertilization

Applying nutrients as dissolved fertilizer in solution.

Macronutrient

Nutrients needed in largest amounts (usually 50 mg/kg) for plant growth (e.g. C, N, O, K, Ca, Mg S, and H).

Micronutrient

Elements or nutrients needed in only small amounts (usually less than 50 mg/kg) for plant growth (e.g. B, Cl, Cu, Fe, Mn, and Zn).

Mineralization

Conversion o fan organic form of an element to an inorganic form (e.g. conversion of organic nitrogen to ammonium nitrogen) by microbial decomposition.

Nitrification

Microbial oxidation of ammonium nitrogen to nitrites and eventually to nitrates.

Organic Matter

Residual decomposition of plant or animal content in soil.

Osmosis

Diffusion of water or any solvent (pure liquid) from a region of greater water potential to one of lesser water potential across a selectively permeable membrane.

Oxidation

Loss of an electron by an atom or molecule where oxygen is the electron acceptor.

Peat

Partially decomposed organic matter accumulating under wet conditions.

Percolation Rate

Downward movement of water through a soil profile.

pH

Degree of acidity or alkalinity. Defined as the negative logarithm of hydrogen ion activity. A scale of 0 to 14 is used where 7 is neutral, below 7 is acidic and above 7 is alkaline.

Sewage Sludge / Bio-Solids

Settled sewage solids removed by screening, sedimentation, chemical precipitation, or bacterial digestion.

Soil

Upper layer of Earth’s surface used as the natural medium for plant growth.

Solute

A molecule dissolved in a solution.

Thatch

Brown to black colored layer of dead turfgrass plant leaves, stems, rhizomes, crowns, and stolons between the green colored vegetation and the soil surface.

Verification

In turfgrass, a method of cultivation where hollow or solid tines are inserted into and removed from the turfgrass and soil to control soil compaction and increase water and air penetration. Hollow tine aerificaiton involves using hollow tines that remove soil cores or plugs while solid tine aerification using solid tines and does not remove any soil.

Water Insoluble Nitrogen (WIN)

Insoluble nitrogen fertilizer fractions associated with urea reaction fertilizers that are insoluble in cold water (72 F).

Water Soluble Nitrogen (WSN)

Soluble nitrogen fertilizer fractions associated with urea reaction fertilizers that are soluble in cold water (72 F).