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PRS™ probes are excellent tools for monitoring nutrients in agricultural systems. Because they measure the plant nutrients that a root is able to find and take up, they identify only the nutrients that are available for plant uptake. This trait allows the supply rate measured by the PRS™ probe to bridge the gaps among soils of different pH and climate and yields a measurement that is virtually independent of location. The factors that vary with changes in soil pH and other soil variables to influence the uptake of nutrients are integrated in the measurement determined by the PRS™ probe because the mechanisms by which the nutrients are taken up by plant roots are mimicked by the PRS™ probe. This allows the PRS™ probe to account for all sources of nutrient supply such as release from soil reserves (both inorganic and organic), release from fertilizer materials, mineralization from manures and organic amendments, and immobilization and mineralization from crop residues. They are able to account in real time for the contribution of legumes to nitrogen availability to the succeeding crop. PRS™ probes are able to integrate all of these factors in evaluation of nutrient supply from new fertilizer products because it is able to measure the nutrient supply at a specific point in the soil. It is able to measure the rate of release of nutrients as they are transformed from one form to another. It is also able to measure nutrient flows into surface and ground waters. The versatility of the measurement tool makes it an effective tool for understanding nutrient transformations in the soil-plant system.

Here are some examples of how the PRS™-probe has assisted scientists to realize their research objectives:

• Salisbury and Christensen (2000) effectively demonstrated differences in release of mineral N to succeeding winter wheat following spring oats and clover. The PRS™ probe was able to measure the reduction in N release as the soils cooled during the early winter period.
  One likely unexpected discovery from this research was the comparison of the release of K observed from the oat and clover residues. Most of the response to cropping after a legume has traditionally been attributed to the response from N fixation of the clover. Some of the observed benefit for wheat following clover was the enhanced supply rate of potassium on these "marginally adequate in K" soils. Traditional chemical extraction would not have predicted the benefit of K supply for the winter wheat crop.
• In similar fashion, Adderley (1998) demonstrated that some of the yield benefit from growing cereals on pea stubble as compared to lentil stubble is due to an increased supply rate of phosphorus. The cumulative supply of phosphorus from pea stubble to the succeeding cereal over a period of 56 days was 25% higher over a comparative lentil stubble.
• Thavarajah et al. (2003) was able to discriminate the N supply rate to young developing cereal seedlings from mid row bands and side bands of fertilizer. She concluded that the early supply rate of N as nitrate to the young developing cereal seedlings was about twice as high for side row banded fertilizer as for mid row banded fertilizer. Differences in phosphate supply rates for the two methods of fertilizer placement were not significantly different.
• The PRS™-probe is an efficient tool for the measurement of nutrients in the environment, both in agricultural ecosystems and in undisturbed settings. Grazing systems are another agricultural system where PRS™ probes have assisted in understanding a complex nutrient cycle. Dr. Vern Baron has been studying intensively rotational grazed pasture systems seeking to develop how to predict the fertilizer inputs to sustain this agricultural system.

PRS™-Probe Related Literature:

• Manure
  1. Qian, P. and Schoenau, J.J. 2000. In Soils and Crops Workshop Proc., pp 274-285. Univ. Saskatchewan. Effect of hog manure on soil phosphorus forms.
  2. Qian, P. and Schoenau, J.J. 2000. J. Plant Nutr. 23: 381-390. Effect of swine manure and urea on soil phosphorus supply to canola.
  3. 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.
  4. Qian, P. and Schoenau, J.J. 2000. Can. J. Soil Sci. 80: 561-566. Fractionation of P in soil as influenced by a single addition of liquid swine manure.
  5. 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.
• Tillage
  1. Adderley, D.R., Schoenau, J.J. and Holm, F.A. 1998. In Soils and Crops Workshop Proc., pp 339-344. Univ. Saskatchewan. Availability of soil nitrogen released from pea and lentil residue to subsequent cereal crops under reduced tillage.
  2. Flaten, B. and Greer, K. 1998. In Proc. of the Wheat Protein Symposium. Univ. Saskatchewan. Nitrogen supplying power of canola versus pea stubble under zero and conventional tillage systems.
  3. 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.
  4. Schoenau, J.J. Campbell, C.A., Beckie, H., and Brandt, S. 1998. In Green Plan: Final Project Report. AAFC. Conservation tillage initiative accounting for nitrogen mineralization and its roles in conservation cropping systems.
• Irrigation
  1. Whitely, K.M., Davenport, J.R., and Manley, S.R. 2000. In Fifth International Conference on Precision Agriculture Proc., pp 453-461. Bloomington, MN. Differences in nitrate leaching under variable and conventional nitrogen fertilizer management in irrigated potato systems.
  2. Whitely, K.M. and Davenport, J.R. 2003. Hort. Tech. 13: 605-609. Nitrate leaching potential under variable and uniform nitrogen fertilizer management in irrigated potato systems.