Precipitation of a substance occurs when:

In solids, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to rapid quenching or ion implantation, and the temperature is high enough that diffusion can lead to segregation into precipitates.

Explanation:

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.