An award given to developers who resumed ruined fields was at first nothing but the right to cultivate the land on a temporary basis, but eventually evolved into permanent rights in the early Heian period, which greatly motivated Tato (wealthy cultivators) and powerful local clans at Gunji (magistrates) level to cultivate fields.
当初は、荒廃田を再開させた開発者には、期限つきで耕作権が認められるに過ぎなかったが、平安時代初期には終身の権利に発展したため、富豪農民（田堵）・郡司級土豪は積極的に開発を行った。