Fungal Functioning and Biosolids

I was enthralled by the interview with forest scientist Suzanne Simard on the Radiolab podcast From Tree to Shining Tree, in which she boldly claimed that the communications network of fungi and tree roots constituted a type of “intelligence.” Then I discovered her TEDTalk, How trees talk to each other, which has had over 1 million viewers. This is exactly my kind of story; where had I been? Her research has shown that “trees talk, often and over vast distances.” Importantly, they share “resources” in the form of carbon and nutrients over wide swatches of forest. Mediating this amazing underground communication network are fungi. Their networks hidden in the soil are analogous to the nerve networks in the human brain, according to Simard.

Dr. Simard offhandedly commented that fungi are a complex life form. I checked with Wikipedia, and learned several amazing things. I read that in today’s understanding of the “tree of life,” while bacteria and archaea each occupy its own domain, the domain of multi-cellular life, the eukaryotes, are now categorized by supergroups (modern classification experts are moving away from the term “kingdom”). One supergroup contains plants, and another supergroup contains animals and also, believe it or not, fungi. Get this, according to the International Society of Protistologists, humans have more in common genetically with fungi that they do with an oak tree.

The key to Dr. Simard’s work is micorrhizal networks, or the mediation by fungi of the movement of food and of other signals between plants vascular plants. In her 2004 research paper Mycorrhizal networks: a review of their extent, function, and importance she asserts “mycorrhizal networks have the potential to influence patterns of seedling establishment, inter-plant competition, plant diversity, and plant community dynamics, but studies in this area are just beginning.” And she has continued to work prodigiously over this past decade.

In digging into this topic, I learned another amazing fact. These mycorrhizal networks are as old as dirt, literally. According to Four hundred-million-year-old vesicular arbuscular mycorrhizae “… the existence of arbuscules in the Early Devonian indicates that nutrient transfer mutualism may have been in existence when plants invaded the land.”

The importance of fungi to the health of ecosystems is now understood to have been a big deal for a very long time.

And this got me thinking of some of the recent work on soil health, a topic which has become very fashionable. Cornell just released its Comprehensive Assessment of Soil Health – The Cornell Framework Manual (3rd edition 2016). The tests offered in this protocol included microbial respiration rate and a measure of an esoteric parameter glomalin, first described by scientists just a mere twenty years ago. Here is Cornell’s definition: "Glomalin is a glycoprotein produced abundantly on hyphae and spores of arbuscular mycorrhizal (AM) fungi in soil and in roots." Ah Hah! Glomalin is a measure of fungal activity.

Arbuscular mycorrhizal fungi, AM fungi, by most accounts are the organisms doing the heavy lifting in connecting plants to soil and to nutrients in a healthy ecosystem. Apparently, if you have lots of glomalin you have lots of AM fungi and you have healthy soil. At least that is hypothesis, one not fully vetted.

The question for us: does land-applied biosolids improve or hurt AM fungal populations and, hence, glomalin levels in soil?

The recent research findings have been good to biosolids. A first pass at the question had raised some concern that biosolids suppressed AM fungi, but this was not seen in subsequent study. In the recent study, Temporal variation outweighs effects of biosolids applications in shaping arbuscular mycorrhizal fungi communities on plants grown in pasture and arable soils, researchers determined that “biosolids application in agroecosystems did not affect mycorrhizal fungi diversity, [nor did biosolids] affect percent root colonisation of arbuscular mycorrhizal fungi.”

Other researchers looked specifically at persistent toxic compounds in biosolids for an effect on AM fungi, and again no adverse effects were seen. In the research paper Effect of biosolids-derived triclosan and triclocarban on the colonization of plant roots by arbuscular mycorrhizal fungi, researchers showed: “A relationship between the concentration of triclosan or triclocarban and colonization of plants roots by AMF was not observed. Biosolids-derived triclosan and triclocarban did not inhibit the colonization of crop plant roots by AMF. [Further,] biosolids had a positive effect on the colonization of the roots of lettuce plants.”

The bottom line is that, if good fungal functioning is an important parameter of soil quality, then biosolids is at least not a negative factor.

Many of us who work with biosolids believe the case is just the opposite, that biosolids is a strong positive ingredient when applied to soil.

We have learned from generations of agronomic researchers that, at a minimum, biosolids can meet most basic crop nutrient needs. This is well documented, as in Washington State’s “Managing Nitrogen in Biosolids.”

Further, our research into the microbiology of biosolids recycling has us address the synergy between biosolids and soil, as when soil microbes assist with the attenuation of biosolids-borne organisms. Even though it is a well-known process, we can be gratified that recent research confirms this: Influence of soil type, moisture content and biosolids application on the fate of Escherichia coli in agricultural soil under controlled laboratory conditions reports that “soil ecological mechanisms are implicated as having a critical role in the fate of enteric organisms introduced into temperate agricultural soil in sewage sludge.”

How biosolids affects soil health is “fertile” research ground even today. While we intuitively understand biosolids benefits, scientists are looking for performance measures in soil health. This is not just for biosolids, but also for a full sweep of agricultural practices and nutrient sources. As explained in Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation “biological relationships are by far the most complex with large deficiencies in basic understanding. Many new tools and techniques have been or are being developed, thus making it more feasible to unravel these complex systems. desperately needs to meet the rapidly increasing food, feed, fiber, and fuel needs of an expanding global population.”

Research is underway today on this topic. Virginia Tech agronomist Greg Evanylo has devoted his research career to this topic, not only for biosolids, but for a wide array of fertilizers, composts, manures and residuals. An example of a practical application of his research is: “Agricultural Management Practices and Soil Quality: measuring, assessing and comparing laboratory and field test kit indicators of soil quality attributes.” Dr. Evanylo is on the WERF High Quality Biosolids project research team that is exploring several specific biosolids formulations as to show how biosolids be better prepared for use in urban soil health. With DC Water launching its new biosolids product, Bloom, this research has special relevancy.

Exciting times are ahead as we illuminate how biosolids helps sustain communications between soil and roots, which, when mediated by our cousins the fungi, is a , in my mind, a wonderous manifestation of an Ancient Intelligence.