Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2009
Publication Date: 11/13/2009
Citation: Blank, R.R. 2009. Effect of temperature on potassium and sodium exchange in a Sierra-Nevada riparian soil. Soil Science Society of America Journal. 74:105-106. Interpretive Summary: There is limited knowledge on the effect of temperature on soil cation selectivity. The effect of temperature of K+ and Na+ selectivity was researched on an A horizon of a Sierra-Nevada riparian soil. Selectivity varied significantly with temperature; K+ was preferentially sorbed over Na+ but the mole ratio decreased significantly at a temperature of 1 degree C. Moreover, the net sorption significantly increased at a temperature of 1 degree C. This increase in cation exchange capacity at low temperatures may have special relevance to ecosystems during snowmelt whence increased retention of certain cations could occur.
Technical Abstract: In the course of investigating nutrient availability in a montane meadow ecosystem of the Sierra Nevada range, it was determined that the proportion of Na+ and K+ on the exchanger phase was significantly affected by season (winter vs. summer and fall). The underlying mechanism(s) controlling this seasonal affect was investigated in the laboratory. Four replicate A horizon samples of a Typic Humaquept (silty clay texture, kaolinitic mineralogy, 3% organic C, pH 5.6) were saturated with Mg+2. Using 5 g subsamples from each replicate, soil was equilibrated for a period of 30 min with 30 mL of a 5.00 mmol solution of Na+ and K+ at 1, 15, 30, and 45 degree C. After centrifugation, supernatant was analyzed for K+, Na+, and Mg+2. Exchanger sorption characteristics varied significantly with T. Overall, K+ was preferentially sorbed over Na+ but the mole ratio decreased significantly at a T of 1 degree C. Moreover the net sorption (K+ + Na+ - Mg+2) was statistically similar to 0 at T’s of 15, 30 and 50 degree C, but significantly increased at a T of 1 degree C. This increase in cation exchange capacity of low T’s may have special relevance to ecosystems during snowmelt whence increased retention of certain cations could occur.