I have barley grains planted in each of the available tiles. The two tiles that are northeast of where i'm standing right now were planted just now, then i zoomed out and immediately zoomed back in. The tile north and northwest of me were planted after zooming back in. The other tiles were planted on previous days.
When I'm planting my fields, i like to plant a little bit each day until I get an agriculture increase and then i come back the next day to plant some more, so I would like the "something has been planted here" image to persist longer than it does.
If I fall asleep, the image also goes away.
The workaround i am using is that i drop my bag of seeds on the next tile to be planted and try to remember what direction i was walking in.