LIFE SCIENCE

Detailed explanation-1: -Although the atmosphere is mostly made up of nitrogen, it is in the form of a gas known as dinitrogen N2. Plants cannot use this form. Dinitrogen, or atmospheric nitrogen, can also be found in the soil.

Detailed explanation-2: -The major source of nitrogen is the atmosphere. It exists as a colorless, odorless, nontoxic gas and makes up about 78 percent of the atmosphere. Nitrogen is also found in the Earth’s crust as part of organic matter and humus.

Detailed explanation-3: -Nitrogen is converted from atmospheric nitrogen (N2) into usable forms, such as NO2-, in a process known as fixation. The majority of nitrogen is fixed by bacteria, most of which are symbiotic with plants. Recently fixed ammonia is then converted to biologically useful forms by specialized bacteria.