Taxonomy, Biology

The traditional science and methodology of classifying organisisms based on physical similarities. Taxonomy is by far the most common method of organizing and classifying organisisms, but is criticized for not reflecting patterns of evolutionary relatedness. (A newer field, cladistics, seeks to address this problem.) Taxonomists classify all organisms into a hierarcy, and give them standardized Latin names. There are seven main levels of classification in the hierarchy:

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

Each level, called a taxon (plural = taxa,) includes all those below it. A given organism belongs to one species, which belongs to one genus, which belongs to one family, and so on. Conversely, a genus can contain one or many species, a family can contain one or many genera, an order can contain one or many families, etc. Scientists often use prefixes like "super-," "sub-," and "infra-" in front of a main taxonomic level, thereby increasing the total number of levels.

Within a particular group of organisims, scientists usually try to give the same "Latinized" ending to the names of all groups at the same taxonomic level. For example, all the Divisions of plants end in "-phyta," and Families of animals usually end in "-idae." This can be a helpful clue as to which taxonomic level you are dealing with. One final tidbit. When referring to a particular species, it is correct to give both genus and species together. The genus is capitalized, but the species is not. Both should be italicized or underlined. As an example, here is the taxonomic classification for the grey wolf:

1. Kingdom: Animalia
2. Phylum: Chordata
3. Sub-phylum: Vertebrata
4. Class: Mammalia
5. Order: Carnivora
6. Family: Canidae
7. Genus: Canis
8. Species: Canis lupus

Taxonomy, Soil

The science of classification of soil.

Tillage

The mechanical manipulation of soil for any purpose but usually to modify the soil physical characteristics to promote crop growth.

Minimum Tillage - the minimum soil manipulation neccessary for crop production.

No-Till - crop is planted directly into the soil without any manipulation since the last harvest. i.e. into standing stubble.

Primary tillage - the operation that contribute to major soil manipulation e.g ploughing.

Tiller

A shoot or culm produced from a crown bud.

Tilth

The physical condition of soil related to its ease of tillage, fitness as a seed bed, resistance to root penetration and seedling emergence.

Top Dressing

Application of fertilizer to the soil surface after the crop stand has been established.

Topsoil

The surface soil manipulated by cultivation. Often called the plough layer approximated as 15cm deep.

Toxin

A poisonous substance produced by an organism.

Trace Elements

Elements that occur or are found in low concentrations typically at the parts per million level. See micronutrients.

Tundra

A treeless artic plain.