if there is a block anywhere directly above a tilled soil block then you cannot plant any crop, it will pop right out of the dirt. idk if this was meant to be but it doesnt matter if the block above is 5 blocks or 200 blocks... it wont stay planted
MCPE-21912
Cannot plant crop with tile above it
Resolved
Cannot Reproduce
0
Given I have (and had for months) underground farms with 2-3 block high ceilings for every type of crop there is, I'm fairly certain your issue is different. I have not seen any issue with them in 1.0.8.1 version either. Make sure your farmland is hydrated and has enough light.
A screenshot of your farmland would make it easy to identify what the issue is.