The hitbox of a normal grass block and the farmland block are the same, but the farmland block is slightly smaller (just as the path block), so there is a slight offset. I'm not sure if this is a bug or just intended but it looks wrong.
Environment
OS X 10.10.3
Linked issues
is duplicated by 3
relates to 4
MC-96434
boats passes through farmland
Resolved
MC-82901
Slight player offset when on Grass Path Block
Resolved
MC-104259
Player / mob stuck on farmland while it changes to dirt
Resolved
MC-260615
Player on a moving boat on top of farmland glitches out of the boat when the farmland converts to dirt, causing the boat to break
Resolved
Confirmed. Does not happen on grass path.