Minecraft 16w44a, Minecraft 1.11 Pre-Release 1
MC-102986, but with farmland blocks.
You can pick block farmland and place it under blocks, when you then update the block (by placing a block next to it for example) the farmland will become dirt (intended).
The farmland would instantly be replaced by dirt, not after a block update.
Steps to reproduce:
In creative pick block farmland.
Place a block (for example planks)
Place the farmland below it.
See it doesn't change to dirt.
Place a block besides the farmland.
See it change to dirt.
Fix: (Based off of Minecraft 1.11, MCP 9.35)