Pieter Bruegel the Elder, The Tower of Babel, 1563
Recently Philippe Bayeve published some commentary on the topic of soil health, under the title Soil health at a crossroads.
His concern - should we call it Bayeve’s Lament? - is that there appears to be a proliferation of meanings for the term but no crisp, generally-agreed definition. In the same way, he points out that there are lists of soil health indicators, and no satisfactory universal quantitative assessment.
He notes that this can lead to miscommunication, misunderstanding, and something less than science.
As a result, he reluctantly concludes that the path forward lies in subscribing to the intent of the soil health journey, as an overarching principle, while always considering the need for a clear definition that guides us to relevant, reliable measures.
By contrast, to gain public support for the importance of soils, he advocates not a simpler definition, but a well-designed advertising campaign.
Elon Musk achieved more for the adoption of electric vehicles, and more energy efficient vehicles generally, by making sexy electric vehicles that lots of drivers would aspire to. Contrast that with the fate of manufacturers whose products were aimed at people wanting to reduce their environmental footprint.
There is much to agree with in Bayeve’s Lament. There are also many lines of thought that deserve more consideration and broader context.
Having a single definition of a concept is uncommon and generally short-lived. Susan Sontag and others have noted that words have two aspects: a core definition and a cloud of association. While ‘red’ can be measured as a narrow range of wavelengths between 625–740 nanometers, there are many cultural associations that form our understanding, and they vary from danger in Western communities to good fortune in Eastern communities. Our narrow definition of a concept leaves it without the context that enables communication. In addition, we need to have a feeling for how that word is understood by our group or audience. People bend the meaning to their purpose, and always have.
This does not mean that there is lots of confusion, it merely means that the meaning of the word or concept is the subject of implicit agreement between speaker and listener. It is unavoidable that policy makers want different content in their discussions about soil health than farm managers want. In fact its a good thing. In this era of integration of separate disciplines, we can expect more of it.
Words evolve in sync with communities, leading to a diversity of communities but who generally share a sense of the limits of the cloud of meanings. The limit is often found by applying the common sense test.
Its irksome at times to hear someone assert that the cloud of meanings for a concept should be construed as the lack of definition, and as an invitation to claim that they perform highly in regards to the vague concept or that it is irrelevant. I grit my teeth when I hear people assert boldly that there is no definition of sustainable agriculture, or of sustainability. There are very good definitions that have been in public discussion for decades.
Initially, soil quality and soil health were concepts that brought soil scientists, agronomists and some farm managers together. They might have shared an interest in concepts like land health, advocated by Aldo Leopold. As a result, the initial soil health indicators seem to include a mix of indicators for farm managers and for soil scientists. Often there are notes in the literature about the need to reduce the count of indicators used. There are papers suggesting indicators so that comparisons can be made between farm management systems such as between organic and conventional.
The purpose for the indicators (and the aspirations of the user community be they scientists or farm managers) form the most important distinction. What matters is that the indicators are sufficient for the purpose, not that they are adaptable to several purposes.
As farm managers incorporate awareness of the significance of soil biology and soil physical condition as well as the familiar soil chemistry into their management practice, I envisage that they will want new indicators that provide guidance earlier than current indicators. Soil RNA or enzyme activity measures may provide earlier guidance on soil organic matter status than current methods of measurement. The new measures will enable adapting the management regime faster.
As well as the evolution of models and frameworks, we continue to make rapid gains in the capacity to measure, and visualise. Scientific and expensive instruments are adapted to industrial level production with a rapid reduction in cost, and consequent expansion in user community. It will continue to affect soil management and measurement. New users will drive demand for further innovation.
As a result, it is unfruitful to try to create a single definition of soil health with a universal set of indicators. Our understanding should evolve and the broadening of the cloud of meanings around a concept should be an indicator, generally, of a spiral of evolution, reflected in the spiral tower shape of the Tower of Babel.
Soil health is now a tool being explored by a range of communities for similar but not identical purposes, and fitness for purpose will be their guide.
To provide a common ground for ongoing discussion between groups however we should consider a resilience measure in soil sampling programs. I suggest that the common sense limit of soil health is that a body of soil should be able to return over time to its original environmental functions, without requiring human efforts. If a body of soil has a low pH or high salinity as a result of human management, we are right to consider it not healthy.
Its important to distinguish between soil functions and soil ecosystem services. The functions exist without human valuing; ecosystem services are those benefits that society currently assigns some significance to. Alex McBratney and other authors in 2019 paper On Soil Capability, Capacity and Condition discuss this distinction:
The notion of soil quality is often defined in terms of the chemical, physical, and biological aspects of the topsoil [1]. The shift from quality to the term soil health is largely characterized by its redefinition to include biological terms [2] to capture the ecological attributes of the soil and improve communication with non-scientists. The term soil condition refers to soil changes compared to a reference state, as a function of management [3]. Soil quality is aligned with the ideas around production, while soil health attempts to expand to include the range of soil functions [4] and ecosystem services [5]. They are primarily focused on the ‘condition’ of the soil, with no explicit statement of a reference state…
The best candidate for reference state, I suggest, is the pedogenon. It is a generic version of the terron/terroir which has specific application to viticulture. In the 2021 publication by Roman Dobarco, McBratney, Minasny and Malone A modelling framework for pedogenon mapping the authors describe a soil unit in new terms:
” …soil entities could be characterized by groupings of homogeneous soil-forming factors under the assumption that the dominant soil-forming processes occurring over a time period within each group are similar, and therefore develop unique soil entities with similar soil properties.”
The pedogenon matches well as the location from which we derive concepts that guide our intuitive sense of soil health. It is a method that farm managers grasp immediately.
The McBratney (2019) paper explores an approach which enables formal comparisons of generic soil functions to be compared with those same functions in soil being managed for human benefit.
As a result we have two separate models, the soil health for productivity, and the soil functions of a reference soil or terron. It enables comparisons of the effects of management for productivity over time and between different management systems.
The soil health journey has a long path ahead but models are available to ensure continued evolution of concepts and the technology to measure them, while providing through the terron, a way to measure and communicate with other communities and interests.
Whether farm managers or policy makers or soil scientists, we can use the comparison of the soil of interest with the pedogenon while entrusting the details to the specialists. It’s what we do with cars: we learn to drive them without understanding all the technology that enables the usefulness we need from them.