Unhealthy plants create unhealthy soils
The popular narrative is that healthy soils produce healthy plants.
This is correct but incomplete.
We need to ask the question, what creates healthy soils? “Healthy plants”, is the right answer.
Without the contribution of plants, soil is just decomposed rock particles; sand, silt, clay.
Plants contribute the carbon, the sugars, the energy that serves as a fuel source, and substrate to develop microbial populations that build organic matter and mineralize nutrients and make them available to plants. The humic substances and humus clay complex are the result of plant contributions to the ecosystem.
Healthy plants create healthy soil.
The key adjective in this statement is ‘healthy’. Unhealthy plants do not create healthy soil. In fact, the opposite.
Unhealthy plants create unhealthy soil.
In this post a few days ago, Robert Kremer described how the root exudates of GMO crops can increase the virulence of soil-borne pathogens. But wait, root exudates are supposed to be a good thing, no?
The influence of root exudates on soil microbial communities is determined by the complexity and quality of the compounds they transmit through the root system, not only the quantity of exudates.
Unhealthy plants will transmit simple carbohydrates, non-reducing sugars, amino acids, and other compounds in ratios that enhance the virulence of pathogens, by providing them with a ready food source.
Healthy plants at higher levels on the plant health pyramid transmit more complex carbohydrates, reducing sugars, polysaccharides, enzymes, and complete proteins, as well as plant secondary metabolites.
Unhealthy plants may also transmit some of these compounds, but in different ratios from healthy plants.
The different ratios of complex carbohydrates, enzymes and secondary metabolites produce a different microbial community response in the rhizosphere.
Unhealthy plants that transmit a lot of simple sugars favor the development of a disease enhancing soil microbial community. They increase the virulence of disease pathogens present in the soil.
Healthy plants that transmit more complex compounds favor the development of a disease suppressive soil microbial community. They decrease the virulence of disease pathogens in the soil, and actually convert them to have a symbiotic relationship with the plant instead of a pathogenic one.
While healthy plants create healthy soils, unhealthy plants create unhealthy soil. This is why focusing on optimizing plant health in the current growing season provides such big soil health rewards.
GMO crops generally have different carbohydrate and amino acid profiles from their non-GM counterparts, which produces a different soil microbial community.