A healthy microbial community within soil combats the effects of drought. Photo courtesy of CIAT
The Texas Transfarmers of Austin, Texas, recently had a meetup at Third Coast Horticulture Supplies. At the meetup, Shawn Bishop, the owner, passed around this easy to understand essay on the importance of soil microbiology. With his permission, I’ve reproduced it here.
Soil Simplified: An Introduction to Your Garden’s Microbial Life
Plants Relationship With Microbes
Until modern times, plants have relied on nutrients provided by their relationship with microbial life. This relationship can seem complex and mysterious. There are however, some key elements to microbial soil life that can enlighten curious gardeners with little more than a brief explanation:
- Plants exude sugars from their roots.
- Bacteria and fungi ingest these sugars.
- Protozoa and nematodes then eat the bacteria and fungi.
- Their excess waste is transformed into “plant available” nutrients right in the root zone.
- The plant uses these nutrients to grow.
- The plant is in control of when and what it eats. By using a piece of its own energy to feed these microbes, the plant insures a future source of energy greater than what it has lost.
Understanding this cycle will help you better learn how plants relate to the soils in which they are grown. Realizing that plants evolved with this relationship can help you decide what is best for your garden.
Soils Relationship to Microbes
Soil is a mixture of organic matter, minerals, and a full spectrum of living creatures.
It is also a microscopic landscape where life decomposes to its base ingredients and ushered into new forms. Gardeners don’t need to know complex biochemistry to know their garden, but understanding some of the processes going on in your soil can be rewarding:
- Fresh organic material is broken down by microbes. The bacteria eat the sugars and fresh green material. The fungi eat the tougher woody material and proteins.
- Plant material is further broken down by larger microbes, small bugs, and worms that feast on the bacteria and fungi.
- Microbes hold moisture and nutrients in their biomass. They keep the water from evaporating and the nutrients from leaching away.
- Bacteria produce slimes that bind particles together to form humus in your soil. This helps the soil store oxygen, creates cracks for water to flow, and provides shelter for the multitude of creatures thriving underfoot.
These are just a few examples of microbial soil interactions that can help you better relate to your garden. Through these processes, the life in your soil maintains balance with the environment that it is a part of.
Working With Soil Biology
If you are adding compost, mulching, or avoiding chemical fertilizers, then you are probably already doing much to improve your soils health. By learning how these actions affect your garden, you can better trust your own reasoning and intuition to guide your relationship with soil life.
Compost is organic matter that has been broken down by microbes so that its energy is stored for further use. Applying it to your garden adds colonies of diverse organisms to the soil.
It also supplies a new food source for existing colonies.
There is much variation in qualities compost can process. For instance, the debris that comprises the compost should be fully broken down and unrecognizable. It should have a deep brown color and rich but subtle smell.
If it smells strong then it is probably potent in some way. If it smells rotten, then it could add problems to your soil. Many methods of producing compost can yield different results, but remember: We evolved with these microbes, plants, and soils as well. Your senses can be the best judge of the quality of compost.
Compost tea is a brew of oxygen rich water, high quality compost, and some foods to help microbes bloom in population.
The goal of good compost tea is to substantially multiply the beneficial organisms.
They can then be used to coat leaf surfaces, inoculate compost, and restore or improve soil health.
A bio film of compost tea on leaf surfaces can keep pathogens from reaching the plant as a food source. The microbes also respire CO2 that helps fuel plant metabolism. Use of tea in compost or soil can drastically increase the biomass of healthy life that stores and converts energy.
Most plants in Earth’s soils have evolved to have a mycorrhizal relationship with fungi. This is when a specialized species of fungi attaches to the root of a plant, and directly exchanges nutrients in the soil for foods from the plant.
The fungi use enzymes and organic acids to break down minerals in the soil and draw them into the plants roots.
The fungal hyphae (strands of cells that form the organism) can multiply the water-absorbing surface area of the root zone by hundreds of times. Use of mycorrhizal fungi spores can greatly increase your plants access to water and nutrients.
Many of the nutrients locked within our soils are in the form of minerals. Some are readily available to plants, while others need the help of microbes to unlock their energy.
When we harvest from our gardens, we deplete the nutrients made available from organic matter and minerals.
We usually replenish organic matter in the form of compost or fertilizers. It is also good to add minerals while restoring fertility to your soil.
Mulch can be a useful tool for dealing with a number of garden issues.
It can keep moisture in the soil, prevent weeds from sprouting, and be a food source for the microbes in your garden.
Mulch should be layered thick enough to accomplish these tasks but loose enough to allow for the flow of oxygen. It can take many forms and each posses unique functions. Try different materials and decide for yourself what’s best for your garden.
Tilling your soil can destroy fungal colonies, damage bacteria, and release precious nutrients back into the air.
Sometimes it is necessary while rehabilitating a landscape to till damaged soil. Compost and compost tea should be applied soon after to inoculate the soil and restore its composition. Hand picking weeds, cover cropping, and mulch can be useful alternatives to annual tilling. When it comes to tillage, less is more.
Everything you do to your garden affects microbial life. With little effort, you can enhance this life for the benefit of your garden, our health, and your environment.