The Nitrogen Cycle. Ammonium (NH4+) and nitrate (NO3â) are the predominate inorganic forms of nitrogen in soils. Ammonium exists in exchangeable and nonexchangeable forms. Nitrite (NO2) and nitrous oxide (N2O) are present in soil in lesser quantities. Plants normally use nitrogen in only the ammonium and nitrate forms. Nitrite is actually toxic to plants. The nitrogen cycle (Figure 5.2) shows reactions that various inorganic nitrogen compounds undergo in soil.
Ridgefield, Washington. Ridgefield is a city in the pastoral, rolling-hills countryside of northern Clark County, Washington, in the United States. The population was 4,763 at the 2010 census.
Ridgefield, Connecticut. Ridgefield is a town in Fairfield County, Connecticut, United States. Situated in the foothills of the Berkshire Mountains, the 300-year-old community had a population of 24,638 at the 2010 census. The town center, which was formerly a borough, is defined by the U.S. Census Bureau as a census-designated place.