Useful Info - GlossaryA B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Absorption: The penetration of a substance into the surface layer of a solid with which it is in contact eg. process by which pesticides are taken into plant tissues by roots or foliage (stomata, cuticle, etc.)
Adiabatic process: A thermodynamic change of state in a system in which there is no transfer of heat or mass across the boundaries of the system. Compression always results in warming, expansion in cooling.
Adjuvant: An ingredient added to a pesticide formulation or mixture to improve its effectiveness. Includes wetting agents, spreaders, emulsifiers, dispersing agents, foam suppressants, penetrants and correctives.
Aeration: The creation of holes in soil or turf by coring, slitting, grooving, hole punching, forking, sliding, spiking or other means to reduce compaction and improve water and air movement through the soil
Carbon cycle: The cycle whereby carbon dioxide is fixed in living organisms by photosynthesis or by chemosynthesis, is consumed in carbohydrate, protein, and fat by most animals and plants that do not carry out photosynthesis, and ultimately is returned to its original state when it is freed by respiration and by the death and decay of plant and animal bodies.
Field capacity: The percentage of water remaining in the soil 2 or 3 days after the soil has been saturated and free drainage has practically ceased. The percentage may be expressed in terms of weight or volume.
Fixation: The process or processes in a soil by which certain chemical elements essential for plant growth are converted from a soluble or exchangeable form to a much less soluble or non-exchangeable form, for example, phosphate fixation.
Humic acids: A mixture of various dark-coloured organic substances precipitated by acidifying a dilute alkali extract from the soil. The term is used by some workers to designate only the alcohol-insoluble part of this precipitate.
Micronutrient: A chemical element necessary in only small amounts, usually less than 1 ppm in the plant, for the growth of plants and the health of animals. Examples of these elements are boron, molybdenum, copper, iron, manganese, and zinc.
Mulch: Any material such as straw, sawdust, leaves, plastic film, or loose soil that is spread on the surface of the soil to protect the soil and the plant roots from the effects of raindrops, soil crusting, freezing, and evaporation.
Nitrogen cycle: The sequence of biochemical changes by which nitrogen is used by a living organism, liberated upon the death and decomposition of the organism, and converted to its original state of oxidation.
Organic: An order of soils that have developed dominantly from organic deposits. The majority of Organic soils are saturated for most of the year, unless artificially drained, but some of them are not usually saturated for more than a few days. They contain 17% or more organic carbon.
Parts per million (ppm): Weight units of any given substance per one million equivalent weight units of oven dry soil; or, for soil or other solutions, the weight units of solute per million weight units of solution.
Perched water table: A water table due to the "perching" of water on a relatively impermeable layer at some depth within the soil. The soil within or below the impermeable layer is not saturated with water.
Pesticides: Chemicals that kill organisms that are injurious to man or to the crops and animals upon which he depends for food, fibre, and shelter. These organisms include insects, mites, microorganisms, weeds, and rodents. Pesticides include insecticides, fungicides, herbicides, and others.
Porphyrin Ring: The versatility of the porphyrin ring, its molecular simplicity and its ubiquity in the biosphere suggest that it was developed a very long time ago. At that time life's chemistry was less elaborate than it is now, and one molecule may have performed many functions. A porphyrin molecule is a planar group of four connected rings, each of which contains a nitrogen atom that faces the center of the ring cluster. These four nitrogens provide an ideal environment for the insertion of a metal ion, such as iron or magnesium, which are extremely useful for a variety of oxygen-related reactions. A particular porphyrin ring containing magnesium is the organic molecule called chlorophyll, the substance in green plants that helps harvest the electromagnetic energy of sunlight for use in photosynthesis.
Rhizobia: Small heterotrophic bacteria of the genus Rhizobium capable of forming symbiotic nodules on the roots of leguminous plants. In the nodules, the bacteria fix atmospheric nitrogen that is used by the plants. The bacteria receive their energy from the plants.
Wilting point (permanent wilting): The moisture content of a soil at which plants (specifically sunflower plants) wilt and fail to recover their turgidity when placed in a dark, humid atmosphere. The wilting point is commonly estimated by measuring the 15-bar percentage of a soil.