Soil teems with microorganisms responsible for breaking down organic matter, releasing compounds that plants absorb as nutrients and improving soil fertility. Healthy soil is living soil, alive with active microorganisms. Assessing the health of soil bacteria is one way to predict the fertility of the soil overall.
Broadly speaking, the dehydrogenases are a class of enzymes that remove a hydrogen atom from a substance and transfer it to an acceptor. They are essential to cellular respiration and are used by microorganisms in the soil to break down organic matter, metabolic processes that occur in abundance in healthy microorganisms.
Respiration is one essential role dehydrogenases play in the metabolism of soil bacteria. As retired Harvard professor John W. Kimball explains on his website, during respiration, food is broken down to release energy. Just like people, bacteria require energy to carry out life functions. Dehydrogenase is one of several enzymes required during this process.
Soil microbes break down organic material found in the soil, a process that requires multiple enzymes, including dehydrogenase. Soil bacteria produce dehydrogenase, which helps them to take apart organic molecules such as sugars and proteins when they encounter them in the soil. This process frees elements, some of which the bacteria use for their own growth and reproduction. The leftovers are available for use by other organisms, including plants.
These activities naturally improve soil health, but dehydrogenase has additional importance to agriculturalists. Dehydrogenases occur only within soil bacteria. They do not act on their own without a bacterial host. Therefore, when dehydrogenase is present in the soil, you can reasonably conclude that bacteria are present and, furthermore, are carrying out the valuable metabolic processes that improve soil fertility.
As explained by the National Agricultural Innovation Project, testing for dehydrogenase activity in soil bacteria involves adding a substance to the soil that serves two purposes. First, it makes organic materials more available to microorganisms. At the same time, the bacteria convert it to a chemical called formazan, which can be extracted from the soil and analyzed. Higher levels of formazan indicate that bacteria are present and healthy, undertaking the metabolic processes that boost soil fertility. Measuring dehydrogenase levels allows researchers to better understand the effect of agricultural practices, such as pesticide use or fertilization methods, on the health of soil.