With spring just around the corner, crocus, tulips and daffodils will be popping their little flower buds up through the cold spring soil. With the return of brighter days and warm sunshine, the grass will turn green again and the tree buds will swell and burst into bloom. This is the spring that we have waited all winter for. But just like a great theater play we only see what is happening on stage not what goes on behind the scenes.
Let’s start at the ground and work our way up. Though the earth appears frozen there is still some activity going on in the soil or behind the stage so to speak. Because the soil temperature is cold everything shifts into slow motion. There can still be root growth, microbial movement as well as moisture and gas exchange, but it is slow. We don’t think of soil as a living thing but it is, and in the winter, it takes a much needed break.
In the spring as the soil temperature increases, the underground activities start to wake up. It is slow at first but by early summer it speeds up like a bustling street in New York City during the rush hour. Much of this activity we cannot see with the naked eye but it is in motion 24/7.
The crews behind the scenes are the microbes in the soil. Members of the “microbe crew” include bacteria, fungi, actinomycetes, algae, nematodes, arthropods and earthworms. Each member of this crew has a job to do to maintain a healthy living soil.
Small but mighty, the bacteria in a gram of soil can number one million and up to 600 million in a highly fertile soil. There are numerous kinds of bacteria that all have their own function. One of their main benefits is making nutrients available to plants. Some bacteria release nitrogen, sulfur, phosphorous and trace elements. Others help to break down soil minerals like potassium, phosphorus and iron. Some release plant hormones that stimulate root growth.
Fungi break down organic matter and release nutrients from soil minerals. Some fungi produce plant hormones that benefit plant growth, while others produce antibiotics like penicillin to fight off microscopic soil borne plant diseases. There are far more beneficial fungi then harmful ones.
Actinomycetes are thread-like bacteria that look like fungi. These microscopic creatures are vital to breaking down organic plant material to release nutrients for hungry plant roots. They also produce antibiotics to fight plant diseases. Some of these are the same antibiotics that are used to treat human diseases. The sweet earthy smell of freshly tilled soil is the result of actinomycetes in the soil.
We often see algae in ponds and lakes in the summer. Many different species of moisture-loving algae live in the upper half inch of the soil. They can often appear as a greenish film on the soil’s surface during wet periods. Algae improve soil structure by producing a slimy substance that helps soil stick together.
There are good nematodes and bad ones. Most are beneficial because they eat up the garbage that microbes leave behind. As a result, nutrients are released for roots to absorb.
Bigger creatures in the soil that we can see are the arthropods — slugs, snails, sow bugs, millipedes, soil centipedes, and springtails. Their job is that of primary decomposers. They eat and shred large pieces of plant and animal material.
Last, but not least, are many species of earthworms. As they work their way through the soil, they create tunnels that help open up the ground to enhance water filtration and soil aeration. Healthy soil with a lot of earthworm activity will increase water absorption anywhere from four to ten times more when compared to soil void of earthworms. Deep earthworm burrows allow better air and gas movement to microbes at deeper depths. Their burrows help stir or mix soils that are not cultivated by man. It is one more way that nature has for stirring the pot or mixing things up.
In the spring as the earth wakes up and plants start to grow, take a moment to acknowledge the crew working behind the scenes. All those creatures underground and out of sight that make the spring blossoms a reality followed by the green, productive beauty of the next growing season.
Margo Hansen is the Director of Bickelhaupt Arboretum.