Question

how does nitrogen get moved from the atmosphere to the earths soil?
how does nitrogen get moved from the earths soil back into the atmosphere?

Explanation:

Nitrogen in the atmosphere is mainly in the form of nitrogen - gas ($N_2$) which is inert. Nitrogen - fixing bacteria in the soil or in root nodules of legumes convert $N_2$ into ammonia ($NH_3$) through biological nitrogen fixation. Lightning can also cause nitrogen and oxygen in the atmosphere to react, forming nitrogen oxides which dissolve in rain and enter the soil. For the return of nitrogen from soil to the atmosphere, denitrifying bacteria convert nitrates ($NO_3^-$) and nitrites ($NO_2^-$) in the soil into $N_2$ or nitrogen - containing gases like nitrous oxide ($N_2O$) through denitrification.

Answer:

How does nitrogen get moved from the atmosphere to the Earth's soil?

• Biological nitrogen fixation by bacteria.
• Lightning - induced reactions forming nitrogen oxides.

How does nitrogen get moved from the Earth's soil back into the atmosphere?

• Denitrification by denitrifying bacteria.