Question

which statement correctly describes how nitrogen in the soil returns to the atmosphere? soil bacteria convert nitrates into nitrogen gas. decomposers directly convert ammonium into nitrogen gas. plants assimilate nitrites and convert them into nitrogen gas. nitrogen - fixing bacteria in plant roots convert

Explanation:

To determine the correct statement, we analyze the nitrogen cycle:

• Denitrification is the process where soil bacteria (denitrifying bacteria) convert nitrates ($\text{NO}_3^-$) into nitrogen gas ($\text{N}_2$), which returns to the atmosphere.
• Decomposers break down organic matter into ammonium, not directly to nitrogen gas.
• Plants assimilate nitrates/nitrites to make organic nitrogen, not release nitrogen gas.
• Nitrogen - fixing bacteria convert atmospheric $\text{N}_2$ to ammonia, not the reverse process of releasing nitrogen gas from nitrates.

So the first option correctly describes how nitrogen in the soil (as nitrates) returns to the atmosphere.

Answer:

A. Soil bacteria convert nitrates into nitrogen gas.