User blog comment:LOTRMod/Farming problems/@comment-26172435-20160113060114

Pondered this over, and I think you've come up with the answer yourself. Let players prepare farmland fir pumpkins and melons by creating a pattern of sand blocks one block below the surface and code the farmer NPCs to sense these 'patches less suitable for planting' and ignore them while hoeing about. :)

It wouldn't conflict too strongly with practical issues in the game nor with realism as a sand subsurface layer improves soil drainage and lower soil humidity, making it less suitable for growing seedlings.