There are several shovels that do not allow you to dig "agricraft" water pads

[astrutzenberg-godaddy]

Specifically these are the blocks that are used to grow the water artichokes in witchery.

I was able to get a repro using the mekanism tool's "steel shovel", and based off a conversation with another player this may also extend to the periodot shovel as well?

Repro Steps:

1. Create a vanilla iron shovel
2. Create a vanilla based hoe
3. till some land with the hoe to turn it into farmland
4. using the steel shovel, right click on the farmland

Results: Nothing happens :D

5. using the iron shovel, right click on the farmland

Results: It generates the empty water pad

Expected results: either tool should work.with this scenario

[RedeyeTheGoblin]

Unfortunately not something that can be changed via config files or MineTweaker, you'll need to report this directly to the mod author.