| Smethurst, PJ; Matschonat, G; Ballard, LM; Dingle, J: Phase partitioning of ammonium in Australian and European forests soils, Communications in Soil Science and Plant Analysis, 30, 2023-2034 (1999) | |
Abstract:
An understanding of phase partitioning of ammonium (NH4) in soils is one of a number of parameters needed to predict the consequences of nitrogen (N) inputs from atmospheric deposition or the application of fertilizers, and for predicting NH4 uptake by roots. However, very few data are available on solid-liquid partition coefficients (Kd) for NH4. The main aims of this study were to determine and compare the Kd values for NH4 in a variety of soils and horizons from Australia and Europe. A Freundlich function was fitted to the sorption or desorption data for each sample and the Kd value calculated at three concentrations (0.001, 0.1, and 1 mM). The Australian study indicated that, although site differences in Kd values were evident at 0.1 mM, variability was too high to distinguish site effects at other concentrations, or depth and plot effects at any concentration. Depth effects were evident at one of the European sites. Despite samples of contrasting origin and different methods of measurement, there was similarity in the Kd values at 0.1 mM for most mineral soils. Organic horizons had higher Kd values at 0.1 mM (8.7-26.2 mL g-1) than most mineral soils (0.3-7.4 mL g-1), but mineral soil at one site had a particularly high Kd value (36.9 mL g-1). In common with other solutes, NH4 concentrations were well buffered at low concentrations (<0.005 mM), but improved precision and accuracy of NH4 measurements at low concentrations will be needed to further improve our knowledge of partitioning at these concentrations. |
