Nothing blows my mind more than coming to terms with the fact that so much of what we see and take for granted hinges on the world that exists naked to the human eye. Think about all of the molecular compounds that make up our physical world, from single-celled organisms to the tallest of mountains. Consider the billions of bacteria happily coexisting inside of your intestines, doing you an irreplaceable service, or the phytoplankton floating in the ocean that are a priceless source of our oxygen. The processes that happen around us are made possible by the most unassuming of participants; they are essential, but not often recognized.
Take compost, for example. That beautiful transition from your unfinished salad and last fall’s leaves to what gardeners call “Black Gold” is driven by the voracious appetites of several different kinds of small organisms. We can see the macrobes (worms, varieties of beetles, black soldier fly larvae, millipedes) but we cannot see the microbes that are the driving force behind decomposition. Without them, we’d be wading in organic matter, and soil – one of our most important and underrated nonrenewable resources – would not be able to successfully regenerate. Looking at the decomposition process at a macroscopic scale ironically misses the bigger picture, but scaling down to the microscopic world gives you the best one.
We can look at the decomposition within a compost pile as a process that occurs in phases. In the first phase, cold-loving psychrophiles kick off the party in the compost heap. The bacterial activity – eat, excrete, reproduce, repeat – slowly begins to heat up the pile from the center outwards. Macrobes are driven to the edges of the pile, and psychrophilic activity levels off. At this new level of temperature, mesophilic bacteria take over. This large category of bacteria comfortably exists in wide range of temperatures, so they end up doing most of the decomposition work in the second phase. Eventually, their hard work makes large portions of the pile unsuitable for all but the most extreme: the thermophiles. Often found in thermal springs (think Yellowstone), thermophiles can handle living in temperatures above the boiling point of water. Within the compost pile, their time is glorious but short-lived. At this point in the decomposition process, human and plant pathogens of concern die off. Within three to five days of this third phase, thermophiles use up available resources and start to become inactive when their decreasing activity levels lead to a drop in temperature. In the fourth phase, mesophilic bacteria once again take center stage while macrobes reintroduce themselves in cooler sections of the pile. As the compost matures, a type of bacteria called actinomycetes may grow in large numbers and become visible as white fungus-like fuzz. Mature compost is stable, nutrient-rich, and ready for use as a soil amendment (not a soil replacement) on gardens and lawns.
Soil management and good compost is all about maintaining a healthy soil food web; with current industrial agricultural practices, we tend to overlook the importance of biodiversity in soil. If you blanket spray fungicides and pesticide over a field, you will not only destroy the organisms that can cause crops distress but also your best microscopic tools for success. You can grow food in “dead” soil with enough synthetic fertilizer, but over time the gains of crop production and overall ecosystem health are less compared to what soils with healthy populations of beneficial microbes can do. Whether they live in a compost heap or in our soils, we need these “beautiful bacteria” because they play a huge role in regulating the ecosystems we depend on. So, show some love for the things unseen and thank the microbes the next time you throw your banana in the compost pile.