Potential measurements between the first and second electrodes {HEAD ~ validate ion transport} between {TAIL ~ the soil} and the first reference electrode 
between
Potential measurements between the first and second electrodes { HEAD ~ validate ion transport } between { TAIL ~ the soil } and the first reference electrode
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH