SPEAKER: A/Prof. Luke Mosley – School of Agriculture, Food and Wine
TITLE: Soil pH: a misunderstood master variable?
Soil acidity is major constraint to agricultural production in Australia, resulting in an estimated $400 million loss in crop production annually. Soil acidification is being accelerated by agricultural practices, its main cause in cropping soils being inefficient use of nitrogen, followed by the export of alkalinity in produce. 4-5 million hectares of cropping land in South Australia currently has surface soil that is acidic, or has potential to become acidic. Soil pH is the key parameter used to assess soil acidification, and is a so-called ‘master variable’ that influences a wide range of biological and chemical processes (e.g. nutrient and metal availability, microbial reactions, CO2 system equilibria, corrosion). Given the importance of measuring pH in soil, how well do we understand this variable? This presentation will firstly outline some of the history, problems and pitfalls associated with conventional soil pH measurements using glass electrodes and electrolyte (e.g. CaCl2) extractant solutions. State of the art soil pH measurements using indicator dye and infra-red spectroscopy and ‘on the go’ sensing technology will be discussed. It will also be highlighted how variable soil pH is at both micro (e.g. rhizosphere) and macro (e.g. paddock) scales.
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