I spent the day in some fields that have not been cultivated this year. After harvesting the potatoes the soil was tilled and left flat. Then turnips were sowed, seeds scattered over the land immediately after cultivation. Since then, apart from picking off the leafy stems of course, no other action has been carried on in this plot. No other crops were rotated, the soil is going to rest so turnips could grow to their full, senesce and produce their seed crop, picked again to be sowed in other fields after a new potato harvest cycle is completed.
Besides a complementary crop with its seasonal sprouts, turnips are used for biological control of weed species. Appropriate cultivation plus turnips seedling vigor shade other competing plants, first forming a cover that occupies almost all available space during the first months, then growing up and using resources that effectively suppress any other broadleaf species.
Well into a new annual cycle turnips are still absolutely dominant in the field.