More on using items that have kedushah shev'it. But why doesn't a lulav from the 7th year have kedushah? Which teaches us that trees themselves (the wood of them) don't have kedushat shevi'it. The sanctity kicks in for that produce that is used for food. Which leads us into a sharp brief focus on what it takes for kedushat shevi'it to kick in. Also, how are you supposed to deconsecrate that which has kedushat shevi'it, once it's present? Naturally, that's a dispute - whether it can be done via redemption (redeeming kedushah is something that is used for other deconsecrations, such as ma'aser sheni), or only via purchase. The daf follows the dispute through its sources and rationale and argument against the other side.