Final answer:
The breakdown of organic nitrogen compounds into ammonia by decomposers and detritivores is called ammonification, which is the first step in nitrogen recycling in ecosystems.
Step-by-step explanation:
The process by which decomposers and detritivores break down organic nitrogen compounds into ammonia is known as ammonification. This process involves bacteria and fungi converting nitrogenous waste from living animals, or from the remains of dead organisms, into ammonium (NH4+). Subsequently, the ammonium is converted first to nitrites (NO2-) and then to nitrates (NO3-) by nitrifying bacteria through the process of nitrification, before the nitrates are finally converted back to nitrogen gas (N2) by other bacteria through denitrification.