Customer Information

Interpretation

Plant Root Simulator (PRS®) Probes have been used for the measurement of soil nutrient supply rate in a wide range of ecosystem types since 1996. A summary of results is provided for the following ecosystems (see notes below):

Ecosystem

Climate

n ('000s)

Burial weeks

Median (25-75%ile)

Nitrogen

Other

Agriculture

Temperate & Tropical

40

32

2 (2 to 3)

Grassland

Temperate & Alpine

26

14

6 (4 to 11)

Arid

Temperate & Tropical

12

8

12 (9 to 16)

Forest

Tropical

3

3

3 (2 to 4)

Forest

Temperate

29

23

8 (4 to 12)

Forest

Boreal

9

8

9 (6 to 18)

Tundra

 Polar

9

6

8 (5 to 10)

Wetland

 Boreal & Temperate

6

6

4 (3 to 4)

Urban

 Temperate & Tropical

2

2

4 (2 to 6)

 

Distribution of all in situ PRS® data with a burial duration of one week or more.  Boxes represent the 25- to 75%ile range and numerical values are median values.  Units are mg/m2 of membrane/burial period (equivalent to ug/10 cm2 of membrane/burial period).  The y-axes for all elements except Ca and Mg are on a log scale.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Notes

  • PRS® data are obtained from a wide range of studies, methods, and soil conditions!
  • Ion adsorption by PRS® probes is non-linear with time (see here).  Most ions on PRS® probes are at equilibrium within a period of one to two weeks, but this depends on both ion and soil properties (dynamic).
  • Approximately 70% of PRS® measurements have been obtained in North America.
  • Nutrient supply rates often positively skewed due to “hotspots” (Johnson et al. 2010, 2011).  This occurs both among and within studies. PRS® data often needs to be log-transformed for statistical analysis.
  • NO3-N supply rates vary over a growing season due to plant uptake and other processes influencing NO3-N bioavailability.
  • NH4-N supply rates are often close to the detection limit, but can be considerably elevated in acid, waterlogged or recently fertilized soils.
  • P supply rates are generally low and sensitive to micro-scale variability due to low mobility.
  • K supply rates are moderately high in most soils, but much lower than Ca and Mg supply rates.  K can be displaced from membranes if both the activity and mobility of bivalent cations are high and burial periods are extended.
  • S supply rates are extremely high in moist soils with high levels of SO4-S (saline soils).
  • The supply rate of Ca within a location is often stable and thus a useful indicator of consistent soil:membrane contact.  The ratio of Ca to Mg is also stable in most soils, depending primarily on soil mineralogy.
  • Fe, Mn, Cu, and Zn are mostly adsorbed by anion rather than cation probes due to addition of EDTA on anion probes and their low mobility as cations.  High Fe and Mn levels (> ~ 20 ug cm-2 burial period-1) are indicative of anaerobic and/or acidic conditions. Anaerobic conditions may also increase P and Pb supply rates.