What is the process called when soil organic matter is decomposed by soil microbes, converting organic nitrogen to ammonium nitrogen?

The correct answer is mineralization, as it specifically describes the process in which soil organic matter is broken down by soil microbes, leading to the conversion of organic nitrogen into ammonium nitrogen. This is a vital component of the nitrogen cycle, allowing nitrogen from organic matter to be transformed into a form that plants can readily uptake.

During this process, microbes consume organic nitrogen sources and release ammonium as a byproduct, which can then be utilized by plants for growth. Mineralization is critical for maintaining soil fertility, as it provides bioavailable nitrogen that is essential for plant health and productivity.

In contrast, volatilization refers to the process where nitrogen in the form of ammonia gas is lost to the atmosphere, which does not contribute to the soil's nutrient pool. Immobilization involves the uptake of ammonium and nitrate by soil microbes, effectively locking nitrogen in microbial biomass instead of making it available to plants. Decomposition is a broader term that encompasses the breakdown of organic material but does not specifically address the conversion of organic nitrogen to ammonium. Each of these terms describes different soil processes, with mineralization focusing on the transformation crucial for plant nutrient availability.