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Glossary for agroforestry

Compiled and edited by Peter Huxley and Helen van Houten, International Centre for Research in Agroforestry - 1997

on-farm experimentation

    1. A generic term to indicate all kinds of scientific experiments that are carried out to evaluate new agricultural technology within the context of existing cropping and livestock systems. Main types are 'on-farm experiments' and 'on-farm trials'.

    2. Experiments aimed at evaluating the biological and technical feasibility of improved technology on farmers' fields. Design and supervision are often the researcher's responsibility.

open community

    See closed community, community

open forest

    A 'forest' where the canopy is not closed and a large proportion of the area does not carry trees.

open loop

    A control system in which corrective action is not automatic but depends on external intervention. Control actions are made without reference to the present output of the system.

open pollination

    Uncontrolled pollination brought about by wind or insects.

open rooted

    See bare-rooted planting

open system

    A system that exchanges matter with the surroundings; it may also exchange energy with the surroundings.

opportunity cost

    The benefit forgone to an individual or society by using a scarce resource for one purpose instead of for its next best alternative use.

ordination

    1. A method for reducing the dimensionality of sets of data with as little loss of information as possible, so that the configuration of the data sets can be examined in various ways. For example, principal components analysis can be used statistically or for pattern analysis.

    2. The ordering of a set of data points with respect to one or more axes. Alternatively, the displaying of a swarm of data points in a two- or three-dimensional coordinate frame so as to make the relationships among the points in many-dimensional space visible on inspection.

organic farming

    The production of crops from land that does not receive and has not received (for a stated period of time) any inorganic inputs (fertilizers, pesticides, and so on). See also alternative farming

organic matter

    1. A general term for plant and animal material in or on the soil and in all stages of decomposition. Readily decomposed organic matter is often distinguished from the more stable forms that have already passed through the stage of rapid decomposition.

    2. Carbon containing materials of either plant or animal origin; exists in all stages of decomposition in soil. See also soil organic matter

organic soil

    Soil containing a high percentage of organic matter (> 20%). See also mineral soil

origin

    For an indigenous stand of trees, the place in which the trees are growing. For a non-indigenous stand, the place from which the seed or plants were originally introduced.

ornamental

    Any tree or plant that is planted for its beauty. This does not mean that it has no other uses. For example, Chlorophora excelsa is often planted as an avenue tree along roadsides (in Uganda); its stately appearance in no way diminishes its usefulness for timber. Ornamentals with other uses in agroforestry are the Cassias and Senna spp. See also multipurpose tree

ortet

    Derived from seeds. See also genet

orthodox seed

    Seed that can be dried and stored at subzero temperatures without damage and with beneficial effects on longevity. See also recalcitrant seeds

orthogonal

    In an experimental design, factors whose effects are estimated independently.

orthotropic branching

    Of branching, stems that only grow vertically. See also dimorphic branching, plagiotropic branching

orthotropy

    Gravitational response that produces a vertical axis. Hence orthotropic shoot with the complex of characters resulting from this response; that is, radial symmetry and vertical orientation. See also plagiotropy

osmotic potential

    See leaf water potential

outbreeding

    1. Mating unrelated parents.

    2. A system of producing progeny sexually that involves the frequent exchange of genetic material between individuals of a population. Outbreeding plants may be self-infertile or have mechanisms to ensure outcrossing.

outcross

    A cross, usually natural, to a plant of a different genotype. See also outbreeding

oven-dry soil

    Soil that has been dried at 105°C until it reaches constant weight. See also air-dry soil

overall application

    Where a fertilizer or herbicide is applied uniformly over the whole crop area, as opposed to band application.

over bark

    Measurement of the diameter or circumference of a trunk or branch made with the bark left on. See also under bark, diameter at breast height

overhead application

    Where, for example, a herbicide is applied over the whole crop area, as differentiated from application directed specifically to weeds.

overlapping cropping

    A cropping sequence where two or more species are grown together on the same unit of land and where the sowing (planting) times do not coincide and the harvesting of one extends beyond that of the other(s); relay cropping is an example.

overstorey

    The portion of trees in a forest stand forming the upper crown cover. See also stratified, understorey

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