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Enlightening Research

Electrical potential differences between soil horizons

The natural electrical potentials (stationary and fluctuating) in soils were studied by our group for last 40 years and the results were summarized and presented on 17th World Congress of Soil Science (Pozdnyakov and Pozdnyakova, 2002). The largest electrical potential differences were observed between soil horizons drastically different in physical and chemical properties. In most soils topsoil has higher electrical potentials than subsoil. The highest potential difference between soil horizons reported for Spodosols (40-60 mV), decreasing to 20-40 mV in Alfisoils and to ~20 mV in Mollisols, and even lower in Aridisols. Probably, the higher potential difference in Spodosols and Alfisols profiles guides growth of woody plants with well developed root system spreading deep into the subsoil. Natural electrical potential differences between soil horizons facilitate root growth. Those differences also form in uniform soil profiles under consistent vertical or horizontal water fluxes. Lysimeter studies on uniform soil column confirm that negative potential gradient forms downwards after intensive infiltration.