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Nitrogen mineralization assessment using PRSTM probes (ion-exchange membranes) and soil extractions in fertilized and unfertilized pine and spruce soils

Harrison, D. J. and D. G. Maynard. 2014. Agricultural Institute of Canada


Several assay approaches that measure mineralizable nitrogen (N) have been used, with varying success, to assess the N supply power of soil. We compared Plant Root Simulators (PRSTM probes, Western Ag Innovations, Inc., Saskatoon, SK) with chemical extractions in an incubation to evaluate how these methods quantify N-mineralization activity of forest soils. Nitrogen mineralization was compared in spruce- and pine-forest soils that had varying N status and had been subjected to 14 yr of N-based fertilization. We paired the assays to determine how the measures co-varied after 1, 2, 4, 6, 8, 10 and 12 wk of incubation. Significant correlations existed between PRSTM probes and extractable ammonium ( ) in the spruce (r=0.567, P<0.001) and pine (r=0.730, P<0.001) soils, although trendlines differed by soil type. Nitrate ( ) PRSTM relationships were evident only in the spruce soils (r=0.916, P<0.001), as the pine soils produced minimal . Both assays provide opportunities for assessing N-mineralization processes in forest soils and differences between assays appear to be related to soil N availability. The PRSTM probes responded primarily to factors affecting ion mobility because of the cumulative nature of the PRSTM probes; whereas the static soil extractions were more sensitive to variations in mineralization and immobilization fluxes.

Key Words

Ammonium, forest soils, inorganic N, laboratory incubation, nitrate