I would not think so as they dont like being disturbed, they dont even like you weeding too close to them. That is what I have been told and have always gone by.Is your seed fresh, as in last years! Parsnip seed has to be last years so make sure so when you buy it.It also needs a decent soil manured the previous year with no stones. My parsnips are Avon Resister a good hardy one , not massive but a good size and disease resistant. Good luck with them , you cannot beat a good roast parsnip, I have just had my last lot from the ground.