PRS probes: From farm field to meadow, forest and bog

Background/Question/Methods

Plant Root Simulator (PRS^TM; Western Ag Innovations) probes consist of ion exchange membranes in a plastic support that can be buried in situ to monitor soil nutrient dynamics. Ion exchange resins have been used for soil nutrient research in many ecosystem types since the mid-1900s, while PRS probes were developed in the early 1990s, primarily for agricultural applications. During the past ten years, research with PRS probes has expanded to include many other types of ecological and environment applications. We analyzed PRS probe use metadata to determine trends in the type of ecosystem and research question in which PRS probes have been used and to assess broad-scale differences in PRS probe data among ecosystems.

Results/Conclusions

PRS probes have been increasingly used in non-agricultural ecosystems.  Of the 185 refereed papers that have presented PRS data since 1992, 130 have been used in non-agricultural ecosystems: from 31% of all papers prior to 2004 to 75% since then.  These papers were primarily from grassland (52%), arctic/alpine ecosystems (21%) and forest (19%), with the remainder from desert or wetland ecosystems. The trends were similar to those observed in the number of graduate student theses and overall projects.

Except for Ca and Mg, PRS measurements were log-normally distributed in all ecosystem types.  Although median values were lower in non-agricultural ecosystems, the range in values overlapped and often exceeded those observed in agricultural ecosystems.

Unsurprisingly, climate change has been the major subcategory with 62 percent of ecology papers in 2013 studying the effects of climate change on various ecosystems. Other major themes addressed with PRS probes were invasive species, varying precipitation regimes and the effects of fire. The use of PRS probes has expanded considerably from its original purpose of crop nutrition planning to a variety of ecological applications, although there are still plenty of opportunities for continued research.