Ruth Rhodes previously worked for The South African Sugar Research Institute (SASRI) as a soil scientist and is now a private consultant, delivered a well balanced and objective presentation on the definition of soil health, highlighting some prevalent factors affecting soil health and methods of quantifying soil health. Rhodes initiated the concept of soil health by highlighting “how every soil tells a story” as illustrated below where two soils that started out identically thirty years ago ended up so different due to land use and management: The “term soil health” today is used interchangeably with the terms “soil quality” and “soil condition” and there are various definitions that are used to describe soil health: A state of a soil meeting its range of ecosystem functions as appropriate to its environment. Soil health / quality describes soils that are not only fertile but also posses adequate physical and biological properties to “sustain productivity, maintain environment quality and promote plant and animal health”- Doron 1994. “how well soil does what we want it to do” – USDA Rhodes pointed out that there are many other definitions however we should want our soils to support and grow optimally yielding crops, “forever” without harming the environment. The soil food web may be used as the starting point in assessing soil health, however there are over forty different factors that determine soil health which can be grouped into biological factors, physical factors, chemical factors and nutritional factors. Rhodes aptly likened these groups of factors to being the pieces of a puzzle and that if on piece was missing then the puzzle is incomplete: Soil health shouldn’t be viewed in terms of biology only as it is comprised by a whole range of different factors, of the these there are only two inherent qualities that we can’t really control and aren’t affected by management easily; soil depth and texture. They are determined by the factors of soil formation such as climate, topography, vegetation, parent material and time which give soils some kind of inherent health or quality for example comparing a loamy soil to a sandy soil. A loamy soil may seen to be more healthy because it has a higher water holding capacity; or referred to as having a higher “soil capability’. Dynamic qualities affect soil quality or condition that we can manage, Rhodes proceeded to briefly highlight some of these factors and how the changing nature of soil properties determining soil health may be affected by management. Chemical and Nutritional factors Soil Acidity is a significant yield limiting factor in dryland agriculture in South Africa especially in KZN and the Eastern Cape and is starting to become a problem in irrigation areas which until recently have not been a familiar with this problem. Soil acidity initially starts off in small patches that expand if not rectified, they can often be identified as areas displaying poor growth (in severe cases not even weeds will grow); “seed vigour” and germination problems resulting from soil acidity have…
