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Microsite assessment of forest soil nitrogen, phosphorus, and potassium supply rates in-field using ion exchange membranes.

Huang, W.Z. and J.J. Schoenau . 1996. Communications in Soil Science and Plant Analysis 27: 2895-2908


A new method for microsite assessment of soil nutrient supply in forest soil was developed. The method involves the use of ion exchange membranes to assess differences in soil nitrogen (N), phosphorus (P), and potassium (K) supply rates in-field over small depth increments in the forest floor (i.e., the L, F, and H horizons). Ion exchange membranes were buried and retrieved from the forest floor in an aspen forest stand in Saskatchewan, Canada. Small (6 mm diameter) sections of the membrane were cut out and ion concentration on the sections measured to provide a nutrient supply rate at that location. Soil nutrient supply rates at the site ranged from 4.6-6.0, 7.3-8.5, 11.6-21.5, and 122-196 mg 10 cm-2 2 h-1 for NH4 -N, NO3--N, P, and K, respectively. On average, the highly humified H horizon had the highest N and P supply rates, followed by the F horizon, with the surface litter (L horizon) having the lowest N supply rates. The simplicity and sensitivity of the procedure make this method appropriate for in-field assessment of differences in soil nutrient supply over small vertical and horizontal distance and was especially appropriate for the forest floor horizons in forest soils.