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.

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.

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.

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).

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.