ABSTRACT
In several disciplines related to agronomy, particularly in soil science and plant physiology, pH has long been regarded as the master variable to be reckoned with. As oxidation and reduction reactions refer to the transfer of electrons, oxidation-reduction conditions can be expressed in volts, by measuring the variable known as redox potential (Eh). Biological activity is itself a major driver of soil structure dynamics. Eh has long been a key focus in disciplines that deal with living organisms, such as microbial ecology, biogeochemistry, bioenergetics, crop physiology, and ecophysiology. Soil Eh and pH and their spatial and temporal variability are related to the soil's physical structure in relation to organic matter and biological activity, including the effects of plant roots. Soil Eh-pH jointly determines nutrient solubility and, as a consequence, plant nutrition. Balanced conditions of soil Eh-pH lead to successful plant nutrition and allow plants to expend a minimum amount of energy to sustain the Eh-pH homeostasis that ensures their health.
