Glossary

aggregates
Units of minerals and organic material cemented together by various actions: carbohydrates produced by bacteria, entanglement by fungal hyphae, electrostatic attraction. The result is a distribution over a wide range of sizes; small particles promote water movement by capillary action, and large sizes facilitate root growth and air flow.
amino acids
The building blocks of proteins. They are made up primarily from nitrogen and carbohydrates, but many also contain sulfur, phosphorus, and other minerals.
anaerobic
Without oxygen. Anaerobic conditions in the soil permit only those organisms which can use chemically bound oxygen. For example, many organisms can remove oxygen from nitrates, resulting in denitrification. Although generally undesireable, an anaerobic environment is occasionally helpful. Some nutrients, such as iron and manganese, are made more available under anaerobic conditions. Anaerobic decomposition is less efficient than aerobic, but anaerobic organisms can attack residues which are too resistant for aerobic organisms. Nitrogen fixation by free-living organisms usually occurs under anaerobic conditions; this is because the enzyme used to aid the process is sensitive to oxygen.
borax
Sodium borate. It is available in food stores and is a suitable fertilizer for supplying boron.
broiler manure
Manure from chickens raised to become broilers. It is usually mixed with wood chips and is drier and not as strong as cage layer manure.
cage layer manure
The unadulterated droppings from confined egg-laying hens.
carbohydrates
Stabilized structures of sugars. Carbohydrates form the skeleton of the plant, and they are a means for storing energy for a long period of time.
cation exchange
A process in which the small number of cations dissolved in the soil water (soluble cations) change place with the much larger number of cations associated the soil micelles (exchangeable cations). This constant interchange establishes an equilibrium between soluble and exchangeable cations which, for example, controls the pH of the soil solution and, to some extent the availability of nutrient cations.
cation exchange capacity
A measure of the ability of the soil micelles to attract cations and keep them in exchangeable form. The exchange capacity depends upon the amount of clay, the type of clay, the organic content and the degree of humification of the organic matter.
CEC
An abbreviation for cation exchange capacity.
chelate
The process by which an organic substance binds a cation having more than one electrical charge. Chelation is similar to cation exchange, with two differences: (1) A chelating organic substance is highly reactive and often water-soluble, while a soil micelle is unreactive and stable; (2) Chelating substances cannot bind cations with a single electrical charge, such as potassium and sodium. In practice, cation exchange holds the majority of the major cation nutrients (calcium, magnesium, potassium), while chelation holds the cation trace elements (copper, iron, manganese, zinc).
C/N ratio
An abbreviation for carbon/nitrogen ratio.
colloidal rock phosphate
A low grade form of rock phosphate, consisting primarily of a fine clay powder. It is the most commonly available rock phosphate for small farmers and gardeners.
denitrification
A process by which bacteria obtain oxygen from nitrates rather than air, during which the nitrogen in the nitrates becomes volatile and escapes; see chapter 10. Nitrogen - Denitrification for details
energy index
A term coined in chapter 2. Essentials of Soil Fertility to denote the energy equivalence, in terms of #2 fuel oil, of an organic substance. It is expressed as gallons of fuel oil per ton of an organic substance.
epsom salts
Magnesium sulfate. It is used as an emergency source of magnesium.
granular soil structure
A well-structured soil, consisting of soil aggregates of varying size.
green manure
An annual cover crop which is turned into the soil just before flowering. It is most often used to smother weeds, to protect the soil over winter, and to hold nutrients that might otherwise be leached. Traditionally a green manure is planted after the harvest of a cash crop, but an alternative is a living mulch; this refers to a cover crop interspersed with a cash crop.
humus
The state of organic residues plus the remains of soil organisms at and beyond the point where the residues are no longer distinguishable as such; the agricultural benefits vary from biological and chemical (nutrient enhancements, pest and disease control) to physical (air and moisture control through a superior soil structure), depending upon the degree of decomposition and consequent stability.
lignins
organic residues characterized by extraordinarily strong chemical bonds among the carbon molecules; they are difficult to decompose; they can be broken down, but at a slower rate and by fewer soil organisms - mostly fungi - than other substances
magnesia
Magnesium oxide, used as an emergency source of magnesium.
micelle
Shorthand for micro-cell, it refers to a colloidal clay or humus particle with a large number of negative electrical charges. It attracts positively charged cations, and the collection of micelles and associated cations are the source of cation exchange.
NPK
A short-hand notation for Nitrogen-Phosphate-Potash.
pH
A measure of the acidity of a liquid in logarithmic units. A neutral solution has a pH of 7. An alkaline solution has a pH greater than 7, and an acid solution a pH less than 7. The pH in soil is the pH of the water in soil; it controls the availability of phosphorus and trace elements and the diversity of soil organisms; the soil pH for most soils is in the range 5.0 to 9.0
rotted manure
Fermented manure which has been stored in a sufficiently compacted state to exclude air
superphosphate
The first manufactured phosphorus fertilizer, prepared originally by dissolving bones in sulfuric acid

© 2013 Robert Parnes

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