|Organic and Compost-based Growing Media for Tree Seedling Nurseries (WB, 1995, 90 p.)|
Activator - added to raw materials to speed up the composting process. This is usually in the form of additional nitrogen (either chemical fertilizer or organic).
Additives - materials used to improve the chemical composition, physical structure, supply micro-organisms, or reduce nitrogen losses in a compost heap.
Aerobic - in the presence of air or oxygen.
Amendments - a material or component added to a growing media to improve its physical or chemical characteristics. Generally does not exceed 10% of the entire mass.
Ammoniation - the lowering of a C/N ratio through the process of adding a source of nitrogen (ammonia, urea, etc.) to a material with which is difficult to decompose quickly (one with a high C/N ratio).
Anaerobic - in the absence of air or oxygen.
Bagasse - the plant residue remaining after the extraction of juices from sugarcane.
Bulk Density - a ratio of the dried weight to its unit volume of material (g/cc).
Carbon/Nitrogen Ratio (C/N) - the ratio of carbon to nitrogen by weight in an organic material. This is an important value when composting.
CEC (Cation Exchange Capacity) - the sum of the exchangeable cations, measured in units called milliequivalent, that a material can adsorb per unit weight or volume - the larger the number, the greater the nutrientholding ability.
Components - the ingredients or materials which comprise a growing media. A component is usually at least 10% of the media.
Humus - complex and stable organic matter resulting from the decomposition of plant and animal material.
Hydrophilic - material which attracts water.
Inoculant - microorganisms (bacteria, fungi, etc.) added to a compost heap in order to promote composting.
Macropores - large air-filled pores in material from which water can drain freely and serves to aerate.
Marc - the residue remaining after a fruit has been pressed.
Mature - when composting material has broken down completely to form humus.
Mesophilic - the lower temperature stage in composting prior to and after the thermophilic stage) during which less active decomposition occurs.
Micropores - the small pores in a media which hold water after gravity has drained excess water from macropores
Organic Fraction - the portion of a media (or soil) consisting of organic material.
Phytotoxic - that which is poisonous to plants.
Pomace - the dry or pulpy residue of material from which a liquid (as juice or oil) has been pressed or extracted.
Porosity - the percent of total volume not filled with solid particles.
Potting Mixture/Media - used interchangeably with growing media to describe the artificial soils used in container nursery culture.
Substrate - any media used in containers in which plants are grown.
Thermophilic - the stage in composting during which high temperatures (45-70 °C) are reached. This stage is necessary for killing pathogens and weed seeds in compost.
Wetting Agents - added to a media to increase the ability to absorb water. Often added when components are hydrophilic.