PRS™-Probe Background

Plant Root Simulator (PRS)™-probes (Western Ag Innovations, Saskatoon, SK, Canada) will be used each year to provide a measurement of soil nutrient bioavailability. The PRS™-probes consist of cation- and anion-exchange resin membranes encased in a plastic holding device, which are inserted into soil to measure nutrient supply over time while causing minimal disturbance (Qian and Schoenau, 2002). Soil temperature and soil moisture data will be collected on a ______ (i.e., hourly, daily, weekly, etc.) basis throughout the duration of the PRS™-probe burial. This will account for the effects of soil temperature on ion diffusion and microbial activity (i.e., mineralization and immobilization) and soil moisture content effects on nutrient availability to plants, specifically through its influence on: physical ion movement; biologically based nutrient cycles (i.e., uptake, mineralization, immobilization, etc.); and, chemical reaction of ions in the soil.

• Qian, P. and Schoenau, J.J. 2002. Can. J. Soil Sci. 82: 9-21. Practical applications of ion exchange resins in agriculture and environmental soil research.

Soil Surface

The PRS™-probes will be placed vertically in the soil to measure the nutrient supply rates of the surface layer. Burying the PRS™-probes directly in the field will provide an integrated nutrient supply rate measurement, based on the principal edaphic factors affecting nutrient availability to plants (Jowkin and Schoenau, 1998).

• Jowkin, V. and Schoenau, J.J. 1998. Can. J. Soil Sci.78:563-572. Impact of tillage and landscape position on nitrogen availability and yield of spring wheat in the brown soil zone in southwestern Saskatchewan.

Note: PRS™-probes are designed for ease of use in the topsoil, therefore, many researchers use the PRS™-probes to measure soil nutrient bioavailability in the top 15 cm of soil. For more references please see papers from peer reviewed journals.

At Depth by Horizon

Nutrient supply rates will be measured in different soil genetic horizons (at _____m) by digging a soil pit and inserting PRS™-probes horizontally (at a slight angle to avoid ponding) into different layers (Huang and Schoenau, 1996). After inserting the PRS™-probes, the excavated soil will be replaced according to horizon in order to maintain as close to original soil environmental conditions as possible.

• Huang, W.Z. and Schoenau, J.J. 1996. Commun. Soil Sci. Plant Anal. 27: 2895-2908. Microsite assessment of forest soil nitrogen, phosphorus, and potassium supply rates in-field using ion exchange membranes.

At Depth Vertical

Nutrient fluxes will be measured at _____ m by digging a soil core using a Dutch auger and inserting a PRS™-probe vertically into the soil. After reaching the desired depth, the auger will be used to loosen up the subsoil prior to PRS™-probe insertion. Each PRS™-probe will be bolted to a 2" PVC pipe enabling their insertion at depth. An adequate amount of water then will be added to redistribute the soil, ensuring adequate contact with the ion-exchange membrane. The top of the PVC pipe will be covered to avoid preferential water flow and accumulation (Dong et. al., 2005).

• Dong, S., Neilsen, D., Neilsen, G.H.,and Fuchigami, L.H. 2005. Plant Soil 268: 357-366. Foliar N application reduces soil NO3-N leaching loss in apple orchards.

Soil Surface

In lab PRS™-probe burials, using intact soil cores sampled from the field and kept at _____ % field capacity, will be used to measure the contribution of mineralization to soil nutrient supply (Qian and Schoenau, 1995).

• Qian, P. and Schoenau, J.J. 1995. Fert. Res. 40:143-148. Assessing nitrogen mineralization from soil organic matter using anion exchange membranes.

By Horizon

In lab PRS™-probe burials, using intact soil cores sampled from the field and kept at _____ % field capacity, will be used to measure nutrient supply rates in different soil genetic horizons. At the appropriate locations along each core 3 cm wide access holes will be cut. Using rubber stoppers the PRS™-probes will be inserted horizontally.

Composite Samples

In lab PRS™-probe burials, using thoroughly homogenized soil sampled from the field and kept at _____% field capacity, will be used to measure the contribution of mineralization to soil nutrient supply (Dijkstra et. al., 2006; Li et. al., 2001).

• Dijkstra, F.A., Cheng, W., and Johnson, D.W. 2006. Soil Biol. Biochem. 38: 2519-2526. Plant biomass influences rhizosphere priming effects on soil organic matter decomposition in two differently managed soils.
• Li, S., Lin, B., and Zhou, W. 2001. Commun. Soil Sci. Plant Anal. 32: 711-722. Soil sulfur supply assessment using anion exchange resin strip-Plant Root Simulator™ probe.

With Root Competition

The PRS™-probes will be buried among plant roots, which will provide a net nutrient supply rate (i.e., measuring the difference between total soil nutrient supply and plant uptake), therefore, yielding a measure of nutrient surplus rather than net mineralization over the burial period. (Blumenthal, 2008; Jowkin and Schoenau, 1998).

• Blumenthal, D. M. 2008. Biological Invasions. Springer Netherlands. Carbon addition interacts with water availability to reduce invasive forb establishment in a semi-arid grassland.
• Jowkin, V. and Schoenau, J.J. 1998. Can. J. Soil Sci.78:563-572. Impact of tillage and landscape position on nitrogen availability and yield of spring wheat in the brown soil zone in southwestern Saskatchewan.

Without Root Competition

The PRS™-probes will be buried inside of root exclusion cylinders (PVC pipe) in order to prevent interspecific competition for nutrients with plant roots; therefore, yielding a measure of net mineralization over the burial period (Adderley et. al., 2006; Sulewski and Schoenau, 1998).

• Adderley, D.R., Schoenau, J.J., Holm, F.A., and Qian, P.Y. 2006. J. Plant Nutr. 29:25-34. Nutrient availability and yield of wheat following field pea and lentil in Saskatchewan, Canada.
• Sulewski, G.D., and Schoenau, J.J. 1998. Can. J. Soil Sci.78:459-466. Can the plant availability of element sulfur be enhanced through its combination with sewage sludge and hydrated lime?.

With and Without Root Competition

Nutrient supply rates and the effect of plant uptake on nutrient supply rate will be assessed using PRS™-probes buried inside and outside of root exclusion cylinders (PVC pipe). The difference between ion flux to the membranes inside (root uptake excluded) versus outside the cylinders will be used as an indicator of plant nutrient uptake over time (Huang and Schoenau, 1997).

• Huang, W.Z. and Schoenau, J.J. 1997. Can. J. Soil Sci. 77: 597-612. Seasonal and spatial variations in soil nitrogen and phosphorus supply rates in a boreal aspen forest.

In Situ

The PRS™-probes will be inserted into peat/wetland at a depth of _____ cm (using a yard stick) and fishing line attached to the handle for easy removal after the burial period. The PRS™-probes circumvent the need to collect and transport frozen cores to lab for analysis. Furthermore, measuring nutrient dynamics in situ provides more biologically meaningful data.

In Lab

The PRS™-probes will be used to measure nutrient release and leaching potential following the application of _. The PRS™-probes will be placed horizontally/vertically on the soil surface below the _____ layer and act as an ion sink for nutrients released over the burial period (Nelson et. al., 2007; Qian and Schoenau, 2002).

• Nelson, J.D.J., Schoenau, J.J., Malhi, S.S., and Gill, K.S. 2007. Nutr Cycl Agroecosyst. Burning and cultivation effects on greenhouse gas emissions and nutrients in wetland soils from Saskatchewan, Canada.
• Qian, P. and Schoenau, J.J. 2002. Can. J. Soil Sci. 82:219-225. Availability of nitrogen in solid manure amendments with different C:N ratios.

Under Plant Residue, Cover Crops, or Following Amendment

The PRS™-probes will be used to measure nutrient release and leaching potential under crop residue and/or following the surface application of _____. The PRS™-probes will be placed vertically/horizontally into the top soil and/or on the soil surface below the _____ layer and act as an ion sink for nutrients released over the burial period.

• In Situ: Arcand, M. M., Lynch, D. H., Voroney, R. P. and van Straaten, P. 2010. Can. J. Soil Sci. 90:257-266. Residues from a buckwheat (Fagopyrum esculentum) green manure crop grown with phosphate rock influence bioavailability of soil phosphorus.
• In Situ: Bair, K.E., J.R. Davenport, and R.G. Stevens. 2008. Hortscience 43(3): 875-880. Release of available nitrogen after incorporation of a legume cover crop in Concord Grape.
• In Situ: Huang, W.Z. and Schoenau, J.J. 1996. Commun. Soil Sci. Plant Anal. 27: 2895-2908. Microsite assessment of forest soil nitrogen, phosphorus, and potassium supply rates in-field using ion exchange membranes.
• In Lab: Qian, P. and Schoenau, J.J. 2002. Can. J. Soil Sci. 82:219-225. Availability of nitrogen in solid manure amendments with different C:N ratios.

Single Burial

Four pairs (i.e., four cation- and four anion-exchange) of PRS™-probes will be spread throughout each experimental unit and then combined for analysis. This will account for soil heterogeneity within each replicate, much like a composite soil sample. The PRS™-probes will be left in soil for _____ days and analyzed to determine the nutrient supply rates over this period (Fortier et. al., 2010; Hangs et al., 2004).

• In Situ: Fortier J., Gagnon, D., Truax, B., and Lambert F. 2010. Nutrient accumulation and carbon sequestration in 6-year-old-hybrid poplars in multiclonal agricultural riparian buffer strips. Agriculture, Ecosystems and Environment. 137(3-4): 276-287.
• In Situ: Hangs, R.D., Greer, K.J., and Sulewski, C.A. 2004. Can. J. For. Res. 34:754-761. The effect of interspecific competition on conifer seedling growth and nitrogen availability measured using ion-exchange membranes.

Intermittent Measurement

The relationship between PRS™-probe nutrient supply rate and plant nutrient uptake and growth will be determined using plots/pots growing _____ and others containing only PRS™-probes. Soil nutrient supply rates will be measured periodically using the PRS™-probes and then compared to plant nutrient uptake and growth throughout the growth period.

• In Situ: Arcand, M. M., Lynch, D. H., Voroney, R. P. and van Straaten, P. 2010. Can. J. Soil Sci. 90:257-266. Residues from a buckwheat (Fagopyrum esculentum) green manure crop grown with phosphate rock influence bioavailability of soil phosphorus.
• In Situ: Qian, P., Schoenau, J.J., and Li, G. 1998. Commun. Soil Sci. Plant Anal. 29:635-641. Potential soil potassium supply capacity as related to wheat potassium demand.

Multiple Burials

Four pairs (i.e., four cation- and four anion-exchange) of PRS™-probes will be spread throughout each experimental unit and then combined for analysis. This will account for soil heterogeneity within each replicate, much like a composite soil sample. A cumulative measure of nutrient supply throughout the growing season will be measured by removing buried PRS™-probes after _____ days and then re-inserting fresh PRS™-probes in the same soil slot. This allows for the assessment of temporal changes in nutrient supply due to changing environmental conditions. Graphing cumulative nutrient supply rates from repeated burials will be used to assess changes in nutrient supply in situ over time (Adesemoye et. al., 2008; Sturite et. al., 2007; Jowkin and Schoenau, 1998).

• In Situ: Adesemoye, A.O., Torbert, H.A., and Kloepper, J.W. 2008. Canadian Journal of Microbiology 54: 876-886. Enchanced plant nutrient use efficiency with PGPR and AMF in an integrated nutrient management system.
• In Situ: Jowkin, V. and Schoenau, J.J. 1998. Can. J. Soil Sci.78:563-572. Impact of tillage and landscape position on nitrogen availability and yield of spring wheat in the brown soil zone in southwestern Saskatchewan.
• In Situ: Sturite, I, Henriksen, T.M., and Breland, T.A. 2007. Annals of Botany 100: 33-40. Longevity of White Clover (Trifolium repens) Leaves, Stolons and Roots, and Consequences for Nitrogen Dynamics under Northern Temperate Climatic Conditions.

Cumulative Measurements in Growth Chamber

The relationship between PRS™-probe nutrient supply rate and plant nutrient uptake and growth will be determined using a growth chamber experiment involving pots growing _____ and others containing only PRS™-probes. _____ % field capacity will be used to measure the contribution of mineralization to soil nutrient supply. Cumulative nutrient supply rates measured using the PRS™-probes will then be compared to plant nutrient uptake and growth at the end of the growth period (Qian and Schoenau, 2000).

• In Lab: Qian, P. and Schoenau, J.J. 2000. Can. J. Soil Sci. 80:203-218. Use of ion exchange membrane to assess soil N supply to canola as affected by addition of liquid swine manure and urea.

Short-term Burial

A short-term (i.e., _____ h/hrs) PRS™-probe burial will be used to measure a “snapshot” of the soil nutrient supply rates to determine the balance of available nutrients in the soil. These short-term assessments of nutrient availability support the modeling of increased nutrient supply over the growing season given an increase surface area of ion sink (i.e., growing root system).

• In Situ: Huang, W.Z. and Schoenau, J.J. 1996. Commun. Soil Sci. Plant Anal. 27: 2895-2908. Microsite assessment of forest soil nitrogen, phosphorus, and potassium supply rates in-field using ion exchange membranes.
• In Lab: Nguyen, H., Schoenau, J.J., Van Rees, K., Nguyen, D., and Qian, P. 2001. Can. J. Soil Sci. 81: 481-488. Long-term nitrogen, phosphorus and potassium fertilization of cassava influences soil chemical properties in North Vietnam.

Long-term Burial

A long-term (i.e., _____ weeks/months) PRS™-probe burial will be used to measure nutrient supply rates throughout the growing season and/or account for the temporal factors affecting nutrient supply. These include ion diffusion from greater distances and the slow-release of nutrients from mineralization (i.e., soil organic matter or organic amendments) and dissolution.

• In Situ: Drohan, P.J, Merkler, D.J., and Buck, B. J. 2005. Soil Sci. Soc Am. J 69:1482-1491. Suitability of the Plant Root Simulator Probe for use in the Mojave Desert.
• In Situ: Dijkstra, F.A., D. Blumenthal, J.A. Morgan, E. Pendall, Y. Carrillo, and R.F. Follett. 2010. New Phytologist. 187: 426-437. Contrasting effects of elevated CO2 and warming on nitrogen cycling in a semiarid grassland.
• In Lab: Qian, P. and Schoenau, J.J. 2002. Can. J. Soil Sci. 82:219-225. Availability of nitrogen in solid manure amendments with different C:N ratios.

PRS™-Probe Analysis Method

After removal, the PRS™-probes will be washed with deionized water, bulked according to treatment plot (anion and cation PRS™-probes that make up one sample are analyzed together), and then eluted for one hour using 0.5 N HCl. The eluate will be analyzed for levels of ammonium (NH₄⁺) and nitrate (NO₃^-) using automated colourimetry flow injection analysis system. Inductively-coupled argon plasma (ICP) spectrophotometry will be used to measure levels of phosphorous (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), aluminum (Al), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), lead (Pb), and cadmium (Cd) in the 0.5 N HCl eluate (Hang et. at., 2004).

• Hangs, R.D., Greer, K.J., and Sulewski, C.A. 2004. Can. J. For. Res. 34:754-761. The effect of interspecific competition on conifer seedling growth and nitrogen availability measured using ion-exchange membranes.

PRS™-Data Reporting

Nutrient supply rates generated with the PRS™-probes are reported as the amount of nutrient adsorbed per amount of adsorbing surface area per time or burial in soil (i.e., µg nutrient 10 cm^-2 time of burial^-1) (Qian and Schoenau, 2002). These nutrient supply rates will be compared with _______throughout the measurement period to test the PRS™-probe capability of measuring soil nutrient bioavailability and predicting _______.

• Qian, P. and Schoenau, J.J. 2002. Can. J. Soil Sci. 82: 9-21. Practical applications of ion exchange resins in agriculture and environmental soil research.

PRS™-Probe Number

For each year of this study, a total of _____ PRS™-probe analyses will be required. One analysis will consist of _____ anion and _____ cation PRS™-probes (i.e., _____ treatments x _____ reps x _____ PRS™-probe analyses per rep).

PRS™-Probe Analysis Agreement

After removal and washing, the PRS™-probes will be sent back to Western Ag Innovations for analysis. The cost of up to four pairs (i.e., four cation- and four anion-exchange) of PRS™-probes is included in the analysis price. Each complete analysis is $___, for a total of _____ dollars (i.e., _____ samples x $______) over a _____ year period.