Glossary of Horticultural Terms

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Here is a short glossary of gardening and horticulture terms for beginners. Also visit the Compost (glossary) and Plant Morphology (glossary) for more information.


Adsorption: the chemical or physical binding of mobile particles to an immobile material, e.g. molecules of water held on the surface of soil particles.

Aggregate: a cluster. of soil particles (e.g. a crumb) held together by cohesive materials such as humus and metal oxides.

Air dry: the dryness of a soil whose water content is in equilibrium with the water content of the atmosphere.

Anaerobic: living or occurring in the absence of oxygen.

Anion: a negatively charged ion, e.g. the chloride ion, Cl-.

Annual Pasture: a pasture that consists of annual species, i.e. plants that live for only one growing season. An annual pasture germinates in the autumn, grows through the winter and spring, and, after setting seed, dies early in the summer.

Aquifer: a water-bearing layer of permeable rock, sand, or gravel capable of yielding significant quantities of water to bores or springs.

Auger: a tool for boring holes in soil; it is frequently used for extracting samples of soil for tests.

Available Water Capacity: the difference between the water content of a soil at field capacity and at wilting point.


Basin Irrigation:
a method of flood irrigation, sometimes used in orchards, by which water is ponded in basins around trees.

Bay: a strip of land, separated from other bays by check banks or ditch banks, to which water is applied during flood irrigation.

Bay Outlet: a structure in the bank of a farm channel through which water is discharged onto a bay.

Border Check Irrigation: a method of flood irrigation on gently sloping land by which water is applied to strips of land (bays) separated by check banks at right angles to the contour.

Border Ditch Irrigation: a method of flood irrigation on relatively flat land by which water is applied to strips of land (bays) separated by the banks of ditches at right angles to the contour.

Bore: a hole of uniform diameter (usually 15 to 60 cm) drilled vertically in the ground to tap an aquifer, and containing a pipe through which ground water can be pumped.


the movement of liquid through narrow tubes as a result of surface forces.

Cation: an ion with a positive charge, e.g. the sodium ion, Na+.

Channel: an artificial water course for supplying water to and within farms.

Channel check: a structure in a farm channel for regulation of the level and flow of water in the channel.

Check bank: a low embankment, used particularly in border check irrigation to check the lateral spread of water and so ensure that the whole of a bay is covered with water.

Clay: mineral particles in soil with a diameter less than 0.002 mm; a soil in which clay particles constitute more than 30 per cent of the mass.

Consistency: the degree of cohesion between soil particles.

Contour Bank Irrigation: a method of flood irrigation on relatively flat land by which water is applied to areas of land separated by check banks that follow the contour.

Contour Ditch Irrigation: see hillside irrigation.

Cut-off Point: the point in a bay which, when reached by the advancing front of water during irrigation, indicates that the flow onto the bay should be stopped so that the water just reaches the end of the bay.


Dethridge Meter:
a wheel with vanes that is used to measure water from supply channels onto individual farms in Victoria and many other parts of Australia.

Drain: a channel for collecting and removing run-off from irrigation and rain.

Drip irrigation: see trickle irrigation.


of application: the proportion of irrigation water applied to land that is used to replenish soil water and to leach salt from the root zone; of distribution: (on the farm) the proportion of irrigation water delivered to the farm that is applied to the land.

Of water use: the proportion of irrigation water delivered to the farm that is used to replenish soil water and to leach salt from the root zone; the term combines the efficiencies of application and distribution on the farm.

Electrical Conductivity: the capacity of a medium to pass an electric current. In an aqueous solution, it increases with the concentration of ions and hence the concentration of total dissolved salts. It is measured in microsiemens per centimetre (~uS/cm).

Electrolyte: a substance that dissociates into ions in aqueous solution.

Emitter: the small tube, nozzle, etc. through which water is emitted in trickle irrigation.

Evaporimeter: an instrument for deter mining evaporation; essentially, it is a pan of water in the open air, and evaporation is measured by the amount of water needed to restore the water level in the pan each day.

Evapotranspiration: a composite term expressing the loss of water resulting from both transpiration (q.v.) by plants and evaporation from soil.


Field Capacity:
the water content of a soil two or three days after it has been saturated by irrigation or rain.

Flood Irrigation: irrigation by flooding of the land.

Furrow Irrigation: a method of irrigation by which water is applied in furrows between rows of plants.


Ground Water:
all free water found in the surface layers of the earth's crust.


Head loss:
in farm channels, if the channel cross-section and the speed of water flow remain fairly uniform, head loss can be taken to be the difference in water level between any two points.

Heavy soil: a soil that requires considerable mechanical or animal power for cultivation; usually, a clay soil.

Hillside irrigation: a method of flood irrigation on steep land by which water is applied to a slope from a channel that follows the contour.

Horizon: a layer of soil, more or less parallel to the land surface, with characteristics such as texture and colour that distinguish it from other horizons. hydraulic conductivity: the rate at which a soil can transmit water by conduction.


Infiltration rate:
the rate at which water enters the soil.

Infiltrometer: an instrument for measuring the infiltration rate of a soil.

Ion: an electrically charged particle that is released on dissociation of an electrolyte (e.g. sodium chloride) in aqueous solution (see also anion, cation, electrical conductivity, electrolyte).

Irrigation: the application of water to land in order to grow crops or increase yields, or both (see also specific methods).


the moving of large volumes of soil to produce the required grade for flood irrigation (to be distinguished from simple smoothing of the surface).

Land layout: the design and construction of channels, drains, and bays for flood irrigation; the resulting arrangement of channels, drains, and bays.

Lateral: a pipeline that supplies sprinklers or emitters with irrigation water; a drain into which surface or subsurface drainage water first flows (see also main, sub-main).

Leaching: the removal of soluble material from soil by the passage of water through that soil.

Leaching requirement: the amount of water passing through the root zone that is required to control salinity.

Light soil: a soil that is easy to cultivate, requiring less power than a heavy soil (q.v.); usually a sandy soil.

Loam: a soil that consists predominantly of sand and silt but with sufficient clay to give it cohesion when moist.


the principal pipeline for the supply of water; the principal drain for the removal of water.

Matric suction: the suction exerted by the soil material (matrix) that induces water to flow in unsaturated soil. It is a negative pressure that results from the combined effects of adsorption and capillarity (q.v.) due to the soil matrix. Water flows from a soil with low matric suction (a wet soil) to soil with a high matric suction (a dry soil).

Moisture block: a porous block of gypsum or nylon that is buried in the soil to indicate the matric suction of the soil by electrical resistance.

Multi-bore system: several bores in close proximity connected to a single pump.


Neutron moisture meter:
an instrument for determining the water content of a soil through the slowing down of fast neutrons by hydrogen atoms.


Organic matter:
the substance of plants, animals, and micro-organisms. The decomposition of organic matter in soil produces further substances that can link soil particles to form aggregates.

Osmosis: the spontaneous diffusion of a solvent (usually water) that occurs through a semi-permeable membrane separating solutions of different concentrations. The solvent diffuses from the less concentrated into the more concentrated solution.

Oven dry: the dryness of a soil after it has been dried in an oven at 105C until it reaches a constant mass.


Parent rock:
the rock from which a soil originated.

Percolation: the downward movement of water through soil.

Perennial pasture: a pasture that consists of perennial species, i.e. plants that live for several years.

Permeability: the ease with which a soil, or a specific soil horizon, can be penetrated by air or water.

Photosynthesis: the formation by plants of carbohydrates from carbon dioxide and water through the agency of light.

Primary-secondary flow: a technique of furrow irrigation or border check irrigation of soils with high infiltration rates; it is used to obtain a uniform depth of water penetration. The furrow or bay is quickly filled by a large flow rate which is then followed by a smaller flow rate that just keeps the furrow or bay filled.

Profile: a vertical section of a soil through all its horizons.


Replenishment water:
the amount of water required to restore the root zone to field capacity; it represents the water taken up by plants and that lost directly from the soil by evaporation.

Root zone: the depth of soil in which most (about 90 per cent) of the roots of a plant occur.

Run-off: water that drains off the surface of land after irrigation or rain.


the content of salts in soil or water; in large enough quantity, these can be detrimental to plants and animals.

Salts: soluble mineral substances present in soil and water.

Salt tolerance: the capacity of a plant to tolerate salts in the soil solution.

Sand: mineral particles in soil with a diameter in the range 0.02 to 2.0 mm; a soil in which sand particles constitute more than 85 per cent of the mass.

Saturation: the condition of a soil in which nearly all of the pores are filled with water.

Silt: mineral particles in soil with a diameter in the range 0.002 to 0.02 mm. spear-point system: see multi-bore system.

Sprinkler irrigation: a method of irrigation by which water is applied to plants through sprinklers.

Stomata: pores through which exchange of gases occurs in the aerial parts of plants.

Structure: the arrangement of individual soil particles into aggregates.

Sub-main: the pipeline that supplies water from the main to the laterals in an irrigation system.

Sprinkler or trickle irrigation; the method that conveys water from the laterals to the pants.

Subsurface drainage: the removal of ground water by means of underground drains or a pump.

Supplementary irrigation: irrigation to increase yield when production itself is not wholly dependent on irrigation.


an instrument for measuring the matric suction of a soil.

Texture: the relative proportions in a soil of the different sized soil particles; the coarseness or fineness of a soil.

Tile drain: an underground drain of earthenware pipes used to control the height of the water table; plastic piping is sometimes used instead of earthenware.

Total dissolved salts: the total salt content of water, expressed in milligrams per litre (mg/l); it may be deter mined by multiplication of the electrical conductivity of the water by 0.6.

Transpiration: the loss of water from plants by evaporation.

Trickle irrigation: a method of irrigation by which water is applied very frequently (often daily) at very low rates from point sources above the root zone.

Tube well: see bore.

Turgidity: the firmness of plant tissue that is caused by the uptake of water and the consequent stretching of the cell wall.


Water content:
gravimetric: the water content of a soil expressed as the mass of water in a given mass of soil; volumetric: the water content of a soil expressed as the volume of water in a given volume of soil.

Water cycle: the continuous circulation of surface waters to the atmosphere (evaporation and condensation), thence to the ground (precipitation), and thence back to surface and subsurface waters (by run-off and infiltration, respectively).

Waterlogged: the saturation of a soil with water for so long that plants cannot grow.

Water re-use: the recycling of surface drainage water by collecting it and using it for irrigation.

Water table: that surface in a ground-water body at which the water pressure is atmospheric (it is taken to be the level at which water stands in wells that just penetrate the water body).

Well-point system: see multi-bore system.

Wetting pattern: the distribution of water throughout a soil after irrigation.

Wilting point: the water content of a soil at which indicator plants growing in that soil wilt and fail to recover when placed in a humid chamber.

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