Systematic Sampling 
An area to sample is evenly divided up into a number that represents the number of samples to be investigated. Using an example 10,000m² area and with 50 samples being required then each division would be 200m². The first (initial) sampling point is located randomly, with all subsequent points being located at an equal irregular interval from the others.
Taxon
A rank of a taxonomic group. The following taxa (which is the plural term of taxon) are widely recognised: Domain or Super Kingdom; Kingdom; Phylum (or Division); Class; Order; Family; Genus; Species. Sub-species may also sometimes be included.
Taxonomy
The scientific identification, description, naming and classification of organisms: animals, bacteria, fungi and plants. The plant (Plantae) kingdom is divided into numerous hierarchical ranks, being called a Taxon.
Temporary Wilting Point
Water transpired by a plant exceeds that which can be supplied by water in the soil resulting in wilting of a plant. This can be common feature in some sports turf situations during hot, bright, and windy summer days, especially where root growth is limited or shallow. There can often be adequate available water within a soil, however, the rate of removal from the soil cannot keep up with the need to keep a plant cool and healthy during these environmental conditions. Once normal, or less extreme, conditions prevail, especially towards the latter part of a day, then the temporary wilting point
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Thigmotropism
The response of a plant due to being touched or coming into contact with an object.
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Threshold
A level at which some action or activity is expected to be taken. In the Integrated Pest Management approach to pest control, this is called 'Action Threshold'.
Tight Cut
Time-Domain Refractometry (TDR)
A method used by a soil moisture meter to measure soil moisture content. It measures the time for electrical signals to travel the length of a sensor-probe and return to determine the volumetric water content of the soil. The progress of the electrical pulse varies according to the moisture content encountered; a higher recorded voltage indicates higher moisture content.
Tolerance
The ability of an organism to withstand, without significant detriment to itself, the effects of an undesirable condition. For example, some plants are more tolerant of saline conditions than others.
Toxic
A situation in which one or more substances or conditions are harmful to an organism, having a significant impact on its health and development, often resulting in weak and poor growth, and where the organism is unable to tolerate the impact then death will typically occur.
The overapplication or excessive presence of many micro-nutrients can lead to a deficiency of other nutrients, with a common response being a reduction in the unit weight and resilience of a plant.