Linearly placed water source blocks create a flow-pull effect on neighboring farmland blocks

I set up a series of linear water source blocks by digging a ditch and then inserting a water source block at every other position (thus filling in the interleaving blocks.). On the neighboring grassland blocks, I treated them with a hoe to create farmland.  For some reason, standing on those farmland blocks will pull you toward (and eventually into) the ditch as if you were being pushed by water flow.  If those neighboring blocks are untreated then no such pull is exhibited.