Olericulture - Branch of horticulture which deals with cultivation of vegetables.

Olland - The aftermath following the harvesting of ha y from a clover Ley.

Omasum - The third stomach of 3 ruminant in which food is ground following partial digestion in the second stomach or reticulum. Also called manyplies or psalterium.

Omnivore - An animal which eats both vegetable and animal foods (e.g., the pig), as distinct from a flesh eating carnivore or a herbivore.

Open Centre - System of training fruit tree where the main stem is allowed to grow only upto a certain height by leading it within a year of planting and inducing gall subsequent vegetative growth by lateral branches, resulting in a lowhead in which bulk of crop is borne to ground that in central leader tree.

Open Furrow - A type of furrow in which the furrow slices are turned in opposite directions so that they lie facing away from each other. Open furrows a re used when completing the ploughing of a land or a field (the finish).

Open-Pollinated Seed - The seed produced as a result of natural pollination as opposed to hybrid seed produced as a result of controlled pollination.

Orchard - An area of' land used for growing fruit trees (e.g., apples, pears, plums, cherries, etc.) either on a small scale or on a more extensive commercial scale. Now-a-days commercial fruit varieties are normally grown on the more dwarfing rootstocks selected for their ability to control t he size, growth, and cropping characteristics, since it is now economically desirable to harvest early in the life of the trees and to do so from the ground or short steps. In addition tree shape is greatly affected by the pruning system used. At the end of their useful life orchards are grubbed, the tendency being to grub trees on dwarf rootstocks at a younger age than those on vigorous rootstocks. Orchards producing desert and culinary fruit are mainly operated by specialist growers, whilst a certain number of orchards producing cider fruit are still combined with livestock grazing.

Orf - A disease mainly of sheep, but also affecting cattle and goats, due to a primary attack by a virus which causes pustules. These are secondarily infected by a fungus (Fusiformis necrophorus) and develop into ulcers and scabs on the lips and mouth, and on other parts including the face, legs tail, genitals, teats, etc. Also called contagious pustular dermatitis, contagious ecthyma, necrobacillosis, of and ulcerative stomatitis.

Organic - A term applied to a substance containing carbon combined with hydrogen, and very often also with nitrogen, oxygen and other chemical elements, farming complex molecules.

Organic Fanning - Systems of farming which avoid the use of artificial fertilizers, pesticides or herbicides, and concentrate on methods of crop rotation and the use of home grown feeds, organic fertilizers and manures, and ley farming.

Organic Fertilizers - Those Fertilizers derived from animal products (e.g. Dried Blood, Hoof and Horn Meal, Shoddy, etc.) and from ,plant residues (e.g., malt culms, castor seed meal) all of which have a considerable nitrogen content. Also applied to more bulky organic materials such as Manures

Organic Matter- 1. The Organic substances in the soil, including animals and plant residues in various stages of decomposition (Humus), cells and tissues of soil organisms (e.g., bacteria, fungi, insects, earthworms, etc. those organic compounds synthesised by such organisms, and organic materials added to the soil as fertilizers, e.g., Manures. The organic fraction of the soil is intimately mixed with the mineral matter. The organic matter content of soil varies according to soil type. On a dry weight basis it is usually in the range 2-15%, but certain organic soils consist almost entirely of organic matter (e.g., peats, black Fen soils). 2. One of the two main components of the dry matter of a feedingstuff (the other beil,1g' Mineral Matter) and consisting mainly of Carbohydrates, Fats and Proteins.


Organophosphorus Compounds - A group of synthetic non persistent chemicals mainly used as insecticides (e.g. Malathion), now-a-days often in preference to the more persistent Chlorinated Hydrocarbons. They may have either a Systemic or a non ­systemic action and mainly affect the nervous system.

Orpington - A general purpose breed of poultry combining both laying and table qualities. Black, buff or white in colour, with white legs and feet, a single comb, and hens laying tinted eggs.

Osier - Any willow grown as a coppice crop, the flexible twigs of which are used in basket making, particularly Salex viminalis. Also called withy.

Other Crop Seed - Seeds of those plants which are grown as crops, other than the main crop.

Out-Crossing - The mating of unrelated animals of the same breed, normally in order to introduce a desired character to the strain which is otherwise absent.

Outfall - The point where a drain discharges into a ditch, or where a watercourse discharges to a river or the sea (sometimes associated with a sluice or flap valve).

Outfield, Out-lying Field - 1. A field situated some distance from the farm buildings usually on the farm boundary.
2. A scottish term for a field under continuous arable cropping without being manured .

Outliers - Livestock kept outside during the winter.

Out-run Land - The open unenclosed areas surrounding a Hill Farm, normally some distance from the farm buildings.

Out-wintering - The practice of keeping cattle in the fields during the winter as distinct from keeping them under cover

Oven Dry Soil - Soil is considered to be oven dry when it has reached
equilibrium with the vapour pressure of an oven at 105°C. The oven dry condition corresponds to a relative humidity of approximately 0 per cent or a pF near 7.

Over Irrigation - Application of more water than is necessary for the needs of vegetation, resulting in loss of water through seepage and leaching with the resultant loss of humus, nitrogen and other mineral elements of the soil.

Overstocked - Condition of overcrowding in tree crops, leading to retarded growth.

Ovine Virus Abortion - Contageous disease of sheep characterized by premature birth or abortion near full term, often accompanied with retention of placenta. The disease is caused by a virus of psittacosis-lympho-granuloma -venereum group.

Oviparous - Laying eggs which hatch to release the young. Birds,
amphibians, most insects and some reptiles are oviparous.

Ox - A general term for a male or female of domestic Cattle. Particularly applied to a castrated male or Steer, especially when used for draught purposes.

Oxidase - A type of Enzyme which acts as a catalyst in the oxidation of substances, removing hydrogen which then combines with oxygen to form water.

Oxidation - The combination of oxygen with a substance, or the removal of hydrogen from it. In cellular respiration,. oxygen reacts with carbohydrates such as Glucose yielding carbon dioxide and water as by-products and liberating energy. This process is comparable to the oxidation of substances by burning, in which energy in liberated as heat. The term is also used to describe chemical reactions in which electrons are lost from atoms such as when ferrous iron (Fe²⁺ ) is oxidised to ferric iron (Fe³⁺ ).

Oxygen - (O). An odourless, colourless, gaseous element, forming about 20%, of the atmosphere and a constituent of water. Essential to most living organisms for respiration and necessary for combustion.

Oxytocin - A hormone secreted by the posterior lobe of the pituitary gland. It is responsible for activating the let-down mechanism, releasing milk from a cow's udder. It also causes the contraction of smooth muscles in the uterus.