A+L Western Method - see humic acid, A+L Western Method

aeration - Aeration commonly refers to the process of using mechanized equipment to either puncture the soil with spikes (spike aeration) or remove approximately 1"x2" cores of soil from the ground (core aeration). Core aeration is done as a means of reducing compaction, reducing thatch buildup, and improving the infiltration of oxygen, water and nutrients.

aggregate stability - A measure of the proportion of the aggregates in a soil which do not easily slake, crumble, or disintegrate.

aggregate structure - See soil structure.


bacteria - A large, widely distributed group of one-celled microorganisms. Some bacteria are disease producing; many are active in processes such as fermentation, the conversion of dead organic matter into soluble food for plants, and the fixing of atmospheric nitrogen.

biological control - Control of pests by the use of living organisms.


cation - Positively charged ions including potassium, calcium, magnesium, and hydrogen.

CDFA Method - see humic acid, CDFA Method

CEC (cation exchange capacity) - The sum total of exchangeable cations that a soil can absorb. The value represents the nutrient-holding capacity of the soil.

compaction - State of being pressed closely together, as soil particles. Soil compaction prevents adequate water and air penetration, and reduces root growth.

compost - A decomposed organic material often used as a soil additive to increase organic matter (OM) content, improve water and nutrient retention, and improve soil structure.


disease - Disturbance in normal functioning and growth, usually caused by pathogenic fungi, bacteria, or viruses.


EC (electroconductivity OR electrical conductivity) - See ECE.

ECE (electrical conductivity of soil extract) - A laboratory measurement used to categorize the relative salinity hazard of a soil. Measured in decisiemens per meter of soil (dSm -1 ). For instance, an ECE > 4 is beginning to become saline for turfgrass growth.

ECW (electrical conductivity of water) - A laboratory measurement used to categorize the relative salinity hazard or total dissolved salts in irrigation water. Measured in decisimens (dSm -1 ).

ESP (exchangeable sodium percentage) - Used to classify sodic and saline-sodic soil conditions. Measured in percentage (%) units of the total sodium in relation to the total exchange capacity of the soil.

evapotranspiration (Eto) - The combination of soil evaporation and transpiration from the plant. Total water loss in vapor form from plant and soil.

F, G

fertigation - The application of fertilizer through an irrigation system.

flocculate - To aggregate individual particles into small groups or granules; used especially with reference to clay and colloid behavior.

fungus - Fungi are microscopic cells that usually grow as long threads or strands called hyphae, which push their way between soil particles, roots, and rocks. Fungal hyphae physically bind soil particles together, creating stable aggregates that help increase water infiltration and soil water-holding capacity. Fungi help prevent soil aggregates from breaking down upon wetting.

H, I, J, K

HumaliteTM - Humalite is a naturally occurring raw material found adjacent to the subbituminous coalfields of Canada. Humalite is a soft, brown coal-like material which has many similarities to leonardite but is very rich in humic acids. See HOGh and Dry HOGh.

humic acid - (Also see HumaliteTM) Humic and fulvic acids (fulvic acids are humic acids of lower molecular weight and higher oxygen content than other humic acids) are commonly used as a soil supplement in agriculture. Humic substances are formed by the microbial degradation of dead plant matter, such as lignin. They are very resistant to further biodegradation. The precise properties and structure of a given sample depend on the water or soil source and the specific conditions of extraction.

humic acid, A+L Western Method - The A+L Western method is a qualitative analysis, designed to report all of the alkaline-soluble humic materials in a sample. It consistently reports a higher percentage of “humic acid” than the CDFA method. It cannot be converted to a “dry basis.” The A+L Western method may mimic some of the industrial process used to extract humic matter from oxidized lignite. However, the base extraction method cannot discretely remove unwanted materials, nor can it prevent the extracted materials from recombining with free radicals or contaminants. Therefore, the A+L Western method more than likely includes non-humic materials as well as humic substances. Source: Mayhew, Lawrence, “Humic Substances in Biological Agriculture,” Acres, Jan-Feb 2004, Vol. 34 • No. 1+2.

humic acid, CDFA Method - The CDFA method is a quantitative analysis of humic acid. This method reports the acid-insoluble fraction of humic material. The analysis is reported on an “as received” basis (includes moisture). The result can be mathematically converted to a dry-matter basis report. The CDFA method is based on the operational definition of humic acid. This technique, however, only uses a portion of the methodology described by the International Humic Substances Society method, which analyzes both humic and fulvic acid fractions. The Standard Methods for Soil Analysis of the Soil Science Society of America, as stated by R.S. Swift in “Organic Matter Characterization,” states that the IHSS method is broadly accepted and can be performed in most laboratories. The CDFA method is a compromise, because the fulvic fractions are completely ignored — the fulvic fraction is actually discarded during the process. Source: Mayhew, Lawrence, “Humic Substances in Biological Agriculture,” Acres, Jan-Feb 2004 • Vol. 34, No. 1+2.

humus - The stable product of well-decomposed organic matter (OM) in the soil.

infiltrate - To filter into; the penetration of water into soils.

infiltration rate - The speed at which water moves into a soil or root zone mixture. Frequently confused with Saturated Hydraulic Conductivity (SHC) - a laboratory procedure used to measure the speed at which water moves through the pores of the soil.


leaching - Downward movement in soil of soluble nutrients or other ions past the rootzone. Removal of accumulated soil salts resulting from irrigation with a saline water source.

lime - Materials containing calcium and magnesium used to neutralize soil acidity and to supply calcium and magnesium as plant nutrients. Aids in soil flocculation; decreases soluble iron, aluminum, and manganese, and aids decomposition of organic matter in acid soils. Lime materials include limestone, shell, marl, and slag.

liquid fertilizer - Plant nutrients applied in solution.

localized dry spot- A dry area of sod and soil which repels water.

M, N, O

macronutrient - Essential elements required in larger amounts for plant growth (e.g. nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, carbon, hydrogen, and oxygen).

micronutrient - Essential elements required in small amounts for plant growth (e.g. iron, manganese, zinc, copper, molybdenum, boron, and chlorine).

nematode - Nematodes are microscopic, wormlike organisms that live in water films and water-filled pore spaces in the soil. Though some nematodes are parasitic and disease causing, the overwhelming majority are nonparasitic. Beneficial nematodes provide nutrient cycling and are important in mineralizing, or releasing, nutrients in plant-available forms.

organic matter (OM) - Material derived from a plant or animal source.

P, Q, R

pathogen - An organism that causes disease.

percolation - The downward movement and filtering of water through the soil.

permeability - A measure of the rate with which air, roots, and water penetrate the soil.

pH - A numerical measurement of the hydrogen ion concentration. The measurement indications of the relative acidity or alkalinity. Values below 7 are increasingly acid; values above 7 are increasingly alkaline.

pore space - The space between solid soil particles or aggregates that is normally filled with water, air, or grass roots.

porosity - Porosity refers to the amount of space between the solid soil particles. Pore space can be filled with either water or air.

porosity, balanced - When a growing media has approximately equal amounts of water-filled and air-filled pore space, the soil is said to have balanced porosity.

porosity, capillary - The percentage of pores in a soil or root zone mixture that retain water after free drainage. This also is occasionally referred to as water-filled porosity.

porosity, non-capillary - The large pores in a soil or root zone mixture that are filled with air after free drainage. Also referred to as air-filled porosity.

porosity, soil total - The degree to which the soil mass is permeated with pores or cavities. The porosity is the sum of the capillary and non-capillary porosity values.

profile, soil - A cross-section of soil that shows the layers or soil horizons.

protozoa – Single-celled animals that feed primarily on bacteria , but also eat other protozoa, soluble organic matter, and sometimes fungi. As they eat bacteria, protozoa release excess nitrogen that then can be used by plants and other members of the foodweb.

recycled / reclaimed / reuse water - A water source not considered of potable quality that has been used for another purpose prior to use as irrigation. Recycled water can include, but is not limited to, treated residential or industrial sewerage effluent, storm runoff and/or recaptured irrigation runoff. These water sources often contain higher quantities of salts than groundwater or potable sources. Recycled water is the preferred terminology.

remineralization, soil (SR) - The process of returning minerals to the soil at levels that approximate the composition of fertile, unweathered ‘young’ soils using finely ground rock minerals. Broad-spectrum minerals provide major, minor and trace nutrients that support healthy plant growth above the soil and promote biological life within the soil.


saline soils - Soils in which there is a heavy accumulation of salts that adversely affects plant growth. Soils are categorized as saline when soluble salts reach or exceed ECe > 4.0 dSm.

saline-sodic soils - Soils with both a high salt content (ECe > 4.0 dSm -1 ) and high exchangeable sodium percentage (ESP > 15%).

salt index - Used to measure the effect of fertilizers on soil solution, and is expressed as a ratio of increase in osmotic pressure produced by a material to that produced by the same weight of sodium nitrate. Download A+L Labs Fertilizer Salt Index Fact Sheet.

saturated hydraulic conductivity (SHC) - A laboratory-determined value measuring the speed at which water moves through the pores of a soil or root zone mixture. The number is expressed in inches or millimeters per hour. SHC is frequently confused with infiltration rate - a term used to describe the speed at which water can enter the soil.

slake - Slaking is the breakdown of large, air-dry soil aggregates (> 2-5 mm) into smaller sized micro-aggregates (less than 0.25 mm) when they are suddenly immersed in water. Slaking occurs when aggregates are not strong enough to withstand internal stresses caused by rapid water uptake. Internal stresses result from differential swelling of clay particles, trapped and escaping air in soil pores, rapid release of heat during wetting, and the mechanical action of moving water.

sodic soil - Soils with a high percentage of cation exchange sites occupied by sodium (> 15%). The high sodium percentage causes infiltration and permeability problems due to de-flocculation of soil particles.

sodium absorption ratio (SAR) - Used to determine whether sodium levels in water will cause soil structure to deteriorate. A ratio of calcium, magnesium, and sodium ions in irrigation water.

adjusted sodium absorption ratio (SAR adj) - A calculated value used to predict an increased sodium hazard of an irrigation source with a high bicarbonate content. A ratio of calcium, magnesium, sodium, and bicarbonate ions in irrigation water.

soil analysis: chemical - The process of determining the relative amounts of nutrients in the soil available to the grass plant.

soil analysis: physical - The process of determining the percentages of sand, soil, and organic matter required for the best physical arrangement of soil separates for a mixture suitable for sports turf root zone mix.

soil foodweb - The soil food web is the community of organisms living all or part of their lives in the soil. It describes a complex living system in the soil and how it interacts with the environment, plants, and animals.

soil health - An assessment of the ability of a soil to meet its range of ecosystem functions as appropriate to its environment. The underlying principle in the use of the term “soil health” is that soil is not just a growing medium, rather it is a living, dynamic and ever-so-subtly changing environment. Soil health is a term used to assess the ability of a soil to: (1) Sustain plant and animal productivity and diversity; (2) Maintain or enhance water and air quality; (3) Support human health and habitation.

soil horizon - A soil horizon is a specific layer in the land area that is parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath. The term 'horizon' describes each of the distinctive layers that occur in a soil. Each soil type has at least one, usually three or four assy horizons.

soil modification - Alteration of soil characteristics by adding soil amendments such as sand, peat, etc.; commonly used to improve physical condition.

soil probe - A tool used to remove a one inch diameter, four to ten inch long soil core from turf areas to examine root development, thatch depth, topsoil depth, soil arrangement, and soil moisture.

soil separates - Particles into which soil can be separated by size without regard to chemical composition, color, weight, or other properties.

soil structure - A property of soils that depends upon the arrangement of soil particles and aggregation. Soil structure is determined by how individual soil granules clump or bind together and aggregate, and therefore, the arrangement of soil pores between them. Soil structure has a major influence on water and air movement, biological activity, root growth and seedling emergence.

soil texture - The relative proportions of the various soil separates in a soil. The coarseness or fineness of the soil.

T - Z

topdressing - A prepared mixture of soil usually containing sand and organic matter to a desired specification. It also may contain physical conditioning materials, nutrients, and pesticides which are spread over turfgrass areas for the purpose of improving the surface, adding to the nutrient-supplying ability of the soil, or applying pesticides. Used for leveling, smoothing, covering stolons or sprigs in vegetative planting, as an aid in controlling thatch, and in maintaining biological balance.

topsoil - A general term applied to the top layer of native or natural soil found on any open land site to be used for agriculture. Normally limited to the uppermost soil horizon referred to as the "A" horizon of soils.

transpiration - Giving-off of water vapor by the plant. Evaporation of water through the stomata.

water analysis - The process of determining the relative amounts of ions (nutrients and salts) in water to determine its quality for irrigation purposes. Used to predict adverse effects upon plants and soil structure.

Sources: USDA NRCS Soils Website, Soil Science Society of America, USGA Glossary, and Wikipedia.