Before this year I hadn’t had the pleasure of hearing Christine Jones speak about regenerative land management practices that will be key to preserving natural resources and feeding the world’s population.
I’d heard a little bit, but not a lot, about the process of “quorum sensing” before the Australian soil ecologist delved into this concept recently at the No-till on the Plains Winter Conference. So what does it mean for your soil life?
In human society, she explains, a quorum is the “number of members of an organization that must be present in order for decisions to be made and business to be transacted.” In the microbial world, the term quorum sensing refers to “density dependent coordinated behavior that regulates gene expression in the microbial population and/or in the host plant or animal.”
“Microbes can’t see, speak or hear,” Jones says, “yet they communicate extremely well — and are incredibly well organized.”
Every species produces its own unique signal and these chemical signals are called “auto-inducers,” she says. “When the concentration of auto-inducers in the environment reaches a critical level, they regulate gene expression in the microbial population and/or in plant or animal hosts.”
Microbes are also multilingual, having a species-specific system — a molecule that says ‘me,’ Jones notes. “Running parallel to that is a second system that’s generic, the language of interspecies communication.”
Jones says this enables microbes to know how many of ‘us’ and how many of ‘them.’ This information is used to decide what tasks to carry out, depending on who’s in the minority and who’s in the majority of any given population.
A plant or animal genome is the complete set of genetic material in that organism, and the major portion of DNA is usually considered inactive, she says. “All of these genes can be influenced by quorum sensing in the embedded and surrounding microbial population,” Jones says.
By detecting biochemical signals, soil microbes can determine how many different kinds of plants are growing in a particular soil. Once the diversity of plants and functional groups of microbes reaches a certain threshold — or ‘quorum’ — everything changes, Jones says.
Quorum sensing in the soil microbiome enables multi-species crops and pastures to function more effectively than monocultures. Researchers have long known that there's more than physical complementarity involved — but until recently haven’t been able to determine the other factors, notes the founder of Amazing Carbon.
"Quorum sensing also helps explain how biostimulants improve plant health, even at very low concentrations,” Jones says. “Effects are more pronounced when two or three different types of biostimulant are combined, at one half to one third the recommended rate. The multitude of biochemical signals mimic plant and microbial diversity, resulting in the production of growth stimulating and plant protection hormones.”
Jones believes quorum-sensing knowledge will become key to harnessing the power of microbes to not only produce food of higher nutritional quality but improve water retention in soils. One study from 2011 suggested quorum-sensing disruption techniques could be used as a tool for plant disease management through the application of Plant Growth Promoting Rhizobacteria (PGPR).
As you can imagine, great things happen with healthier soils. Jones says organic carbon content in the soil is the key determinant of water-holding capacity and is often the most limiting factor in farm production. Soil organic carbon is also the driver for the nutritional status of plants, and “therefore the nutritional status of animals and people.
"Water retention isn’t just important for agriculture, but in buffering the effects of climate change, Jones adds. She says it’s a scientific fact that water vapor accounts for 95% of the greenhouse effect that is causing climate change. “If we’re serious about reversing climate change we need to put the water back in the soil where it belongs,” Jones says.
Regardless of where they fall on the climate-change issue, I think most farmers in semi-arid regions will agree that maximizing soil moisture retention is vitally important to their operation’s success.
So again, it boils down to choices. There’s no way you can build more carbon in your soils and put microbes to work for you without having at least some plant diversity that will accomplish that task. If you don’t have enough plant diversity on your farm, make it a goal this year to take a step in that direction.