The Journey Towards Global Soil Health Indicators.

The concept of Soil Health has gained considerable traction over the last few years. It has evolved from the concept of Soil Quality, which largely described the inherent and management-imposed physical (‘tilth’) and chemical (nutrients) of soils, and generally in relation to agriculture. Soil Health differs from this production-oriented viewpoint to explicitly include the consideration of living organisms in the soil as our partners in the drive towards ecosystem service delivery from optimal soil function.

Despite the vast complexity of terrestrial systems – geology, climate systems, vegetation and anthropogenic perturbation – there appear to be, perhaps incredibly, common rules to the responses and presentations of soils at the field-scale that are recognisable and useful to land managers, and that provide tantalising clues to the underlying microscale processes at work. We now understand that Soil Health is an emergent property arising from as yet poorly understood combinations of physical, chemical and biological mechanisms in soils that drive soil systems towards common observable and measurable phenomena that we describe as ‘Soil Health Indicators’.

The question remains: are all Soil Health Indicators (SHIs) created the same?

As a starting point to addressing this conundrum, we investigated widely recognized and accepted SHIs (soil organic matter content, dry aggregate friability and stability in water, colour) and explored their applicability to soils in temperate (UK) and tropical (South America and Africa) farmed environments. We subjected the soils to intensive analyses of physical, chemical and biological processes to determine whether the mechanisms that give rise to SHIs are similar regardless of geographical location. We hope to determine underpinning empirical evidence that is common to the manifestation of SHIs, and ultimately describes the stage in the journey along a continuum of Soil Health that could be used by land managers to improve the function of their soils.