Nitrogen Cycle
Nitrogen Cycle is the way nitrogen moves through air, soil, plants, and back again.
Think of it this way
A kitchen counter holds three bowls: one for air, one for soil, and one for plants. Small dots move from the air bowl into the soil bowl, carried by tiny helpers. The soil bowl passes those dots to the plant bowl, feeding the roots. Dead leaves fall back into the soil bowl, and some dots float up to the air bowl to start again.
Explaining nitrogen cycle by grade level
Plants need nitrogen to grow big and strong. Tiny living things in the soil change nitrogen into food that roots can drink up. When old leaves fall and rot, nitrogen goes back into the soil. Then new plants use it all over again.