From wine to truffles, conniseurs of such flavors, keenly observe the terroir of their favourite delicassies. Appreciating that an ecosystem imparts distinctive qualities and nutrients, that we can taste and benefit from. Though soil plays a vital role in this equation, our interest and knowledge of its science over the centuries is fragmented. Fortunately, a resurgence and respect for soil is on the rise. Climate change has influenced the balance required for fertile ground, but there are still ways to improve if not rewild the earth we rely on.
In this article: Dr. Elaine Ingham, unearths potent concepts in soil science, driving a biological approach to agriculture which revitalizes microorganisms to create a robust Soil Food Web.
The biological approach to growing plants uses life-based management which requires an understanding of how plants interact with below-ground and above-ground organisms. Conventional agriculture uses a chemical / mechanical engineering approach to plant production focused on adding inorganic fertilizers (salts) to replenish missing soluble nutrients, and toxic chemicals to control unwanted weeds, diseases, and pests.
These two approaches conflict sharply in their basic view of how the world functions. One major difference is their understanding of what soil is; a growing medium for plants (biologically based) or merely an inert matrix to keep plants from being washed away when it rains (chemical approach).
Biological agriculture recognizes that as soil builds, structure improves, nutrient cycling begins anew, infiltration and water-holding capacity re-establish, preventing erosion, soil keeps soluble nutrients, and weeds, pests and diseases reduce if not are completely prevented. All these benefits accrue as the proper set of organisms return to the soil. Soil is all about life; if that life is killed, crushed, or otherwise eliminated, plants cannot get the full nutritional balance needed to benefit by animals, including humans.
The overuse of tillage, applications of large quantities of inorganic fertilizers, pesticides and herbicides in Conventional agriculture destroys soil by physically, through tillage and compaction, and chemically, through each application of toxic chemicals. Once the beneficial life in the soil is extinguished and the organisms required to perform the benefits (mentioned above) are lost, it leaves farmers to grow plants in dirt (Montgomery, D. 2007. Soil erosion and agricultural sustainability. PNAS.Org).
Hans Jenny, considered one of the Father’s of Soil Science, clearly explained the difference between soil and dirt. He points out that dirt refers just to the mineral part of soil ( i.e. sand, silt, clay, rocks, pebbles, gravel, parent material, bedrock). These materials contain the spectrum of nutrients which plants require however, they are locked in the crystalline structure of these minerals and are inaccessible. Converting those mineral forms of nutrients into plant-available forms can only be done by living soil organisms, in the proper balances. (Ingham, E., Moldenke, A., & Edwards, C. (2000). Soil Biology Primer [Gov]. NRCS Soils).
Plants are very much in control of making nutrients bioavailable to other plants. Plants release exudates, which are mixtures or sugars, amino acids and carbohydrates, straight from above-ground photosynthesis, which “tell” specific species of the bacteria and fungi to make enzymes to solubilize the nutrients from the crystalline structures of sand, silt, clay, rocks, pebbles, parent material, and organic matter.
The bacteria and fungi store this material in their bodies and use it to grow more bacteria and fungi. The increasing populations of bacteria and fungi attract predators to the root system—because that’s where exudates are released from the plant—most bacteria and fungi are then eaten by those predators.
Because the nutrient concentrations in the bacteria and fungi are so much greater than the concentration of nutrients needed by the predators (protozoa, nematodes, micro arthropods, earthworms), the predators release the excess as plant nutrients. Think of this system as being like getting pizza delivered to your house—the plants “order” their pizza by paying out exudates, and the pizza arrives in precisely the forms that plants require, such as sulfate, phosphate, and chelated calcium.
Another way for soil life to bring nutrients to the plant known as rhizophagy cycle, outlined by researchers, involves the plant releasing exudates to grow bacteria, the bacteria use their enzymes to pull nutrients from mineral and organic material, and then the bacteria are “invited in” to the root tip, whereupon the plant can get the nutrients in the bacterial cells. The plant then escorts the bacteria out of the root, having extracted some nutrients the plant needs (White, J. F., Kingsley, K. L., Verma, S. K., & Kowalski, K. P. (2018). Rhizophagy Cycle: An Oxidative Process in Plants for Nutrient Extraction from Symbiotic Microbes. Microorganisms, 6 (3), 95).
Yet a third way that plants can get nutrients from soil is to engage mycorrhizal fungi to colonize their root systems. Once the fungi attach up to the root cells, the plant will feed the hyphae inside the root (exudates) which cause the fungi outside the root to take-up the nutrients and cycle them back to the plant. (Ingham, E., Moldenke, A., & Edwards, C. (2000). Soil Biology Primer [Gov]. NRCS Soils).
We need to learn to work with nature and not try to fight it. There are no “wastes” in natural systems, and to be sustainable, to increase our ability to produce fully nutritional food for humans, we need to understand how nature put systems together that recycle everything.
As scientists keep looking, we are discovering more and more ways that plants do not need inorganic fertilizers added to soil to flourish. Inorganic fertilizers, tillage, and pesticides kill the microbes that supply nutrients to plants, completely disrupting how nature performs this process. We can extend agriculture production for a short time by adding inorganic fertilizers, but it is not financially feasible to add back all the all the nutrients plants need to be healthy. Human health will suffer as we eat food lacking the needed balances of nutrients.
Dr. Elaine Ingham, is the Founder of Soil Foodweb. Her goal is to empower people to bring the soils in their communities back to life using the science of the Soil Food Web. Dr. Ingham’s biological approach has been used to restore the ecological functions of living-soils all over the world, ensuring healthy, strong plants and super-nutritious food, whilst eliminating soil erosion and the need for chemical inputs.
Feature photo: Ants are important ecosystem engineers that have a large impact on the soil food web. This is reflected in the alteration of soil properties by ants due to burrowing activities, the accumulation of organic matter and other nutrients in the soil, which, in turn, alters soil physical, chemical and (micro) biological processes. (E. L. H. Cammeraat, A. C. Risch (2008). The impact of ants on mineral soil properties and processes at different spatial scales, Journal of Applied Entomology).
