Some form of irrigation items would be a nice implantation.
Like ones used in farms today across north America.
Like a well it can b built any where but cost of which would be affected by the water tables, use of these will prevent the drop in crop Quality but the water Quality itself should not affect the the Quality of crops.
(some have suggested that this should increase the cap in Quality that irrigated crops can jump)
As an example a turnip planted at Q100 would not drop below that Quality when irrigated but it can still stay at that Quality or go up to a max of 105.
These should have 2 built pieces the base (where the water it pulled from) and the extensions(pieces that irrigate/water).
Extension pieces should be able to be walked through or planted under but no picese are movable.
Instead of moving extensions should irrigate the area of a 3x3 9x9 square.