National Ambient Air Quality Standard; federal standards specifying the maximum allowable levels (averaged over specific time periods) for regulated pollutants in ambient (outdoor) air


A plant or animal indigenous to a particular locality.

Native species

Flora and fauna species that occur naturally in a given area or region. Also referred to as indigenous species.

Natural environment

The natural environment comprises all living and non-living things that occur naturally on Earth. In its purest sense, it is thus an environment that is not the result of human activity or intervention. The natural environment may be contrasted to “the built environment”, and is also in contrast to the concept of cultural landscape.

Natural resources

Nutrients and minerals in the soil and deeper layers of the earth's crust; water; wild and domestic plants and animals; air; and other resources produced by the earth's natural processes.

Natural selection

One of several gradual mechanisms through which evolution occurs. Process by which a particular beneficial gene (or set of genes) is reproduced more than other genes in succeeding generations due to selective pressures in the environment that favor the beneficial gene. The result of natural selection is a population that contains a greater proportion of organisms better adapted to certain environmental conditions.


Microscopic soil worm, which may attack roots or other structures of plants and cause extensive damage

Net area sown

It is the net area sown under crops, the area sown more than once during the year being counted once only

Net farm income

The money and non-money income form operators realize from farming as a return for labor, investment, and management after production expenses have been paid. Net farm income is measure in two ways net farm income before inventory adjustment and net farm income after inventory adjustment. Net farm income doesn't include changes in the value of inventories such as crops and livestock at the end of the year


A chemical element essential to life and a primary plant nutrient. Animals get nitrogen from protein feeds; plants get it from soil; and some bacteria get it directly from air

Nitrogen cycle

Cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment.

Nitrogen draft

 Incorporating high-carbon matter like wood chips into the soil (i.e., mixed into soil, not placed on top) can cause deficiencies in the nitrogen available to plant roots. Organic matter composts and, in order to compost, the high-carbon material requires the nitrogen from the soil to create the desired diet for microbial action.
N-p-k N-p-k is an abbreviation for nitrogen (n), phosphorus (p), and potassium (k). In the chemical philosophy, these three elements are considered important to force crop production (as opposed to the organic philosophy goal of improving the biodiversity of the soil). U.s. law requires that the ratio of these three elements be specified on every bag of commercially-available fertilizer. A ratio of 3-1-2 or 4-1-2 is considered good.

Nitrogen fixation

A process whereby nitrogen fixing bacteria living in mutualistic associations with plants convert atmospheric nitrogen to nitrogen compounds that plants can utilize directly.

Noise pollution

Noises that disturb the environment and people’s ability to enjoy it, for example continually sounding house alarms, loud music, air conditioning or other electrical units and aircraft or motor engines


Not able to be consumed and/or broken down by biological organisms. Non-biodegradable substances include plastics, aluminum, and many chemicals used in industry and agriculture. Particularly dangerous are non-biodegradable chemicals that are also toxic and tend to accumulate in organisms.

Non-point Pollution

Pollutants that cannot be traced to a specific source, including storm water runoff from urban and agricultural areas

Nonrenewable resource

Resource that exists in a fixed amount (stock) in various places in the earth's crust and has the potential for renewal only by geological, physical, and chemical processes taking place over hundreds of millions to billions of years. Examples are copper, aluminum, coal, and oil. We classify these resources as exhaustible because we are extracting and using them at a much faster rate than they were formed.

Normal Farming Practices

The customary and generally accepted activities, practices and procedures that farmers consistently adopt, use, or engage in the production and preparation for market of crops, livestock, and livestock products and in the production and harvesting of agricultural, agronomic, horticultural, silviculture, aquacultural crops and commodities.

No-till Farming

See zero till.

Noxious gases

Poisonous gases that can harm people and the environment. Some gases have a strong smell, for example sulphur dioxide and methane, while others, such as carbon monoxide, do not have any smell at all.



A substance or recognized plant nutrient, element, or compound which is used or sold for its plant nutritive content. The term can include livestock and poultry manures, compost as fertilizer, commercially manufactured chemical fertilizers, sewage sludge or any combination thereof


Any food or element an organism must take in to live, grow, or reproduce. Plant: An essential element in a particular ion or molecule that can be absorbed and used by he plant. For example, carbon, hydrogen, nitrogen, and phosphorus are essential elements; carbon dioxide, water, nitrate, and phosphate are respective nutrients. Animal: Materials such as protein, vitamins, and minerals that are required for growth, maintenance, and repair of the body and also materials such as carbohydrates that is required for energy.