Around the middle of the Heian period, the ritsuryo governmental system collapsed, a system whereby shoen and kokuga region were governing units was established and the contents of kanno gradually changed.
平安時代中期ごろに律令制が崩壊し、荘園・国衙領を支配単位とする体制が確立していくと、勧農の内容も次第に変質していった。