Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Decomposers increase the fertility of the soil and prevent dead organisms from building up in the environment. In which way do decomposers make the soil more fertile?
by adding nitrogen
By breaking down organic matter into simpler compounds, releasing essential nutrients.