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Use of ion-exchange membrane to assess nitrogen-supply power of soils

Qian, P. and J.J. Schoenau . 2005. J. Plant Nutr.28:2193-2200

Abstract

Soil nitrogen-supply power (NSP), including nitrogen (N) mineralized from organic matter, for crop growth is an important criterion in evaluating soil quality. Ion-exchange membranes in the form of a Plant Root Simulator (PRS)™ probe were used to measure ammonium and nitrate release rates as a measure of NSP in 54 Saskatchewan soils with contrasting pedogenic and management histories. Two incubation systems (aerobic and anaerobic), with ion-exchange membrane probes placed in situ, were conducted to predict NSP. The 54 soil samples were also used in two growth-chamber studies to assess patterns in plant N uptake by canola. Soil type had a profound influence on available N-supply rates, with soils of higher organic-matter content due to climatic conditions, slope position, and past management having higher NSP values. Good relationships (R2 = 0.54 and 0.69) between NSP and canola N uptake were observed. The N-supply rate values used as an index of NSP as predicted by two-week aerobic incubation for Brown, Dark Brown, and Black soils in Saskatchewan were 200-550, 550-1100, and > 1100 μg nitrate-N/10cm2/2 wks, respectively, with different management histories producing significant variation within a region.

Key Words

anion exchange membrane, cation exchange membrane, nitrogen supply power, nitrogen mineralization, canola