Redox potential as a soil health indicator – how does it compare to microbial activity and soil structure?

Abstract

Background and aimsRedox potential is a promising soil health indicator, which integrates the combined effect of chemical oxidation–reduction reactions into a single measurement. However, this method has been tested only on a few soils. The aim of this study was to test redox potential as a soil health indicator, to see if it responds to management practices and to compare it with existing soil health metrics for microbial activity (“CO2burst”) and soil structure.MethodsWe collected 35 soil samples in agricultural fields from a carbon farming trial, where contrasting management practices have been applied to increase carbon stock. The soil samples were dried, rewetted and analyzed for redox and microbial respiration during rewetting. In addition, soil structure, texture and organic matter content was measured. The data was analyzed for correlations between the indicators and for the differences between management and control fields.ResultsRedox was well correlated with microbial activity, structure, and texture. A low redox state was connected to high microbial activity, indicating bioavailable organic matter availability. Soils with good structure had an oxidized redox status, possibly reflecting high gas-transport. The carbon farming practices resulted in lower oxidation, possibly due to build-up of plant residues.ConclusionsThe findings supported the use of redox as a soil health indicator, but highlighted further research needs for identifying the shared mechanisms linking structure, redox and microbial activity. As such, redox can be a low-cost additional measurement to map changes in soil health, but it cannot replace existing structure or microbial activity measurements.