total Kjeldahl nitrogen

Total Kjeldahl nitrogen is the total concentration of organic nitrogen and ammonia nitrogen.

traditional farming

The original farming method handed down from generation to generation. It involves the intensive use of indigenous knowledge, natural resources and cultural beliefs of the farmers.

transpiration

Water discharged into the atmosphere from plant surfaces.

tree-rings

The layer of wood growth put on a tree during a single growing season. In the temperate zone, the annual growth rings of many species (e.g., oaks and pines) are readily distinguished because of the differences in the cells formed during the early and late parts of the season. In some temperate zone species (e.g., black gum and sweetgum) and many tropical species, annual growth rings are not easily recognized.

triploidy

A cell, tissue, or organism having three sets of chromosomes.

triticale

The grain of an intergeneric hybrid of Triticum x Secale (wheat and rye)

trophallaxis

The mutual exchange of food between insects, especially between adults and larvae in social insects.

trophic levels

A description of community structure based on the relationship between the production, consumption, and decomposition of energy (food) by organisms. Primary producers such as algae, herbivores such as deer, and carnivores such as wolves represent three different trophic levels.

tundra

Arctic or subarctic regions where tree growth is limited due to low temperatures, the short growing season, and the permanently frozen subsoil. Dominant vegetation consists of grasses, sedges, mosses, lichens, and dwarf shrubs and trees.

udic regimes

A soil water regime where soil moisture is sufficiently high to meet plant needs throughout the year. This regime is common for soils in humid zones and is typical for about one third of the worldwide land area.

uglifruit

Fruit of the hybrid of the grapefruit (Citrus paradisi) and tangerine (Citrus reticulata).

understory

A layer of vegetation (such as saplings in a forest) that is below the canopy but have cleared the ground level vegetation.

uneaten food

Food waste is a component of food loss and occurs when an edible item goes unconsumed, as in food discarded by retailers due to color or appearance and plate waste by consumers.

Universal Soil Loss Equation

An equation used for the design of water erosion control systems. A = RKLSPC wherein A = average annual soil loss in tons per acre per year, R = rainfall factor, K = soil erodibility factor, L = length of slope, S = percent of slope, P = conservation practice factor, and C = cropping and management factor.

vacuum packaging

The packaging of processed products in which air is removed and a vacuum is formed. Carbon dioxide gas or nitrogen gas may be introduced into the package to help eliminate the oxygen. Removal of the air retards growth of aerobic bacteria.

value-added products

Products that generally have increased in value due to processing.

value chain

The network of firms that bring products to market, from companies that produce raw materials to retailers and others that deliver finished products to consumers. Economic value is added through the coordinated management of the flow of physical goods and associated information at each stage of the chain.

vascular plants

Plants containing specialized vascular tissue (xylem and phloem) which are more highly evolved than such bryophytes as mosses and liverworts. Vascular plants include ferns, gymnosperms, and angiosperms.

vector competence

The physiological ability of a vector organism to acquire, maintain and transmit an infectious agent, as described by susceptibility to a pathogen, immune response, and sustaining infection long enough for disease transmission to occur.

vectorial capacity

The capability for disease transmission by a vector to a host, as influenced by behavioral, ecological and environmental factors, such as population density, host preference, feeding habits or frequency, duration of latent period, or longevity.