Well rice fields are common in Japan and it seems like it a custom in Inakadate. A few others fields in rural Japan also followed the trend. The fields there are common from the 90's and it seems like the tradition is changing every year.
This site is in Japanese and has the years labeled next to them so you can see its becoming a tradition.
http://www.am.askanet.ne.jp/~tugaru/z-inakadate.htm