KANcycling does an intermittent series called RiceWatch in which we try to catalogue all of the different ways people deal with rice stalks after threshing. Here’s another entry: round barrel-like shapes. Often these are encased in white or black (or even garish blue-green) plastic, so you see fields decorated with round colored dots.

This was the route I was most unsure of, since I didn’t know anything about the Nayoro area. Luckily, I can recommend it: following this river north was extremely pleasant with alternating hilly scenery and fields and farms in the distance. The route was by no means level, though, so be prepared for some climbing.