When, for example, hydrogen ions on {HEAD ~ the resin} are being exchanged for cations in {TAIL ~ the soil}, there is a tendency for the soil pH to be depressed 
When , for example , hydrogen ions on { HEAD ~ the resin } are being exchanged for cations in { TAIL ~ the soil } , there is a tendency for the soil pH to be depressed
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH