The Soil Food Web with Dr. Elaine Ingham
April 13-17th, 2015
For the eighth year in a row, GreenFriends Farm hosted Dr. Elaine Ingham, a world renowned soil biologist, for a soil food web workshop. Participants came from around the country and from as far away as Germany.
The 5-day Soil Food Web workshop, held April 13-17th, featured hands-on lectures on the soil food web, composting, compost tea and more. The soil food web is the intricate network of organisms above and below ground that provide the basis for all plant life on earth and therefore most life. Participants learned how to make and evaluate good compost that benefits the right microorganisms for their plants needs.
On the last day people brought soil samples from their farms, their gardens, or just went outside to collect samples from the orchard. Putting those samples under the microscope was proof that everything they had learned in the past few days was true. The soil is alive.
Most people don’t realize that the soil beneath their feet is teaming with life. A mere teaspoon of garden soil can contain up to 1 billion bacteria, several yards length of fungi and thousands of protozoa. These beneficial soil microorganisms are not human pathogens. In fact, they outcompete human pathogens, such as E.coli, that might be harboring in the soil.
The soil food web is directly involved in getting nutrients from the soil to the plants and eventually to you. Plants convert sunlight into sugars through photosynthesis. These sugars are then secreted through the roots as exudates. Exudates are simply compounds that are secreted from the roots to feed the bacteria and fungi. Or, as Dr. Ingham puts it, they are the “cakes and cookies” the plant uses to lure in the bacteria and fungi that provide it nutrients.
The bacteria and fungi extract nutrients from the soil and decompose organic matter. They keep nutrients in the root zone so that they are available to plants. They also enhance soil structure by binding soil particles into aggregates, thereby improving the flow of water and oxygen and preventing inhospitable waterlogged, anaerobic soil.
Protozoa, nematodes, microarthropods and earthworms are considered predators in the soil food web because they eat the bacteria and fungi. This causes the release of the nutrients stored in the bacteria and fungi, in a soluble, plant available form. Because they are larger organisms, they further improve soil structure by burrowing and creating air and water passages. They also enhance decomposition of organic matter and mix it into the soil.
When plants have the nutrients they need, made available by the soil food web, inorganic fertilizers are not needed. Toxic pesticides and herbicides are un-necessary because beneficial organisms, or “the good guys,” as Dr. Ingham puts it, outcompete plant pathogens. Pesticides not only destroy plant pathogens, but also destroy the biology of the soil, essentially turning it into lifeless dirt, devoid of nutrition.
Establishing the soil food web is not difficult. Even better, it is cheaper than using conventional fertilizers and pesticides. The key is to feed the microbes that feed the plants. It simply requires some good compost.
On day three of the workshop, participants trooped out into the bright afternoon sunshine and gathered on a green hillside. They examined components of good compost: woody material for fungi, green material for bacteria and organic material high in nitrogen, such as legumes. Good compost should not smell bad and should have a rich dark color.
Dr. Ingham explained that life above ground is directly intertwined with life below ground. Microorganisms that increase the porosity of the soil increase the water-holding capacity of the soil. This allows roots to go deeper and reduces or eliminates the need for irrigation. This is incredibly important for drought-stricken places, like California.
The workshop participants explored GreenFriend Farm’s 700 tree fruit orchard and took soil samples. Dr. Ingham recommended ways to improve the soil biology so that the tree roots could go deeper and access more water.
The entire food web must be present Dr. Ingham emphasized. Nutrient retention cannot happen without fungi and bacteria in the root systems. These nutrients are made available to the plants by protozoa, beneficial nematodes and microarthropods. All of these organisms work together to enhance soil structure so that oxygen and water can flow freely. The roots will grow deeper, the plants will be healthier, and so will you.