Getting to the Root of Crop Nutrition.

Conventional soil testing is based on the premise that a chemical extraction will reflect the soil nutrient supply to plants.  The shortfalls of this approach have been evidenced by the numerous studies conducted over the past 50 years aimed at improving soil test methods.  Radiotracer studies in the 1960’s where pivotal in shifting thinking away from amounts and toward mechanisms of supply.  Barber (1995) first coined the term soil nutrient bioavailability to describe the flux of ions to plant roots.  Our presentation will build on this concept by describing how we can use an ion exchange membrane as a plant root simulator (PRS™).  This simple absorbing surface affords a new tool to integrate the factors controlling ion supply allowing us to ``see what the plant sees``.  Ion supply over time from biologically active soils allow for a much more realistic picture of the soil nutrient supply.  These plant root simulators also account for ion movement dynamics that impact the supply to the plant root.  Combing this powerful functional test of soil nutrient supply with simulation models of root growth and plant demand has given ecosystem managers of the 21^st Century a new way of “getting to the root of crop nutrition”.