Pot Grown Carrots - Re-using the compost

Yep I've used spent compost too with some sand mixed in and some top soil to make up the volume as I was making an old recycling box in to a carrot box and needed the volume. I generally reuse the same box each year, just dig out the top half of the soil, stir some fertiliser of some variety in to the lower soil, then put the old stuff back on. Makes the carrots nice and straight and very little forking.