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