AP BIOLOGY

Detailed explanation-1: -Plant and animal wastes decompose, adding nitrogen to the soil. Bacteria in the soil convert those forms of nitrogen into forms plants can use. Plants use the nitrogen in the soil to grow. People and animals eat the plants; then animal and plant residues return nitrogen to the soil again, completing the cycle.

Detailed explanation-2: -This process is called nitrification. Compounds such as nitrate, nitrite, ammonia and ammonium can be taken up from soils by plants and then used in the formation of plant and animal proteins. An interactive showing the main components of the terrestrial nitrogen cycle.

Detailed explanation-3: -Plants absorb nitrogen from the soil as both NH₄⁺ and NO₃⁻ ions, but because nitrification is so pervasive in agricultural soils, most of the nitrogen is taken up as nitrate.