Soil Composition For Root Veggies

David Trammel's picture

Missouri has an extremely high clay content in its soil. Even worse in urban areas because builders often leveled the individual yards with fill dirt. Unless you take several years to amend your bed soil with organic material it makes growing root veggies difficult. So I've been looking at a variety of ways to provide a looser medium for things like carrots and potatoes. One way is to add a large amount of sand.

This video is a good example.
"How to Grow Fantastic Carrots in Sand Boxes"

Yes, you can do this in containers like 5-gallon buckets but I like what this guy does, build tall (18 to 24") raised beds. It puts them all in one more easily cared for raised beds.

I think instead of having to dig out the soil with a shovel, I would make the front of the box removable. Cover each panel with plastic to protect it, have an internal cross piece of
wood or even metal to hold its shape, and then just unscrew the front and let the sand come out onto a tarp to reuse. Or maybe use galvanized roofing panels?

He fills the bed first with a good supply of large particle-sized sand. I might also add something like vermiculite for drainage, and to provide a loose growing medium. Then he cores the sand and adds a fine compost in the holes. I've never seen coring done before in a video. That would save from having to fertilize the entire bed, sand included. I also like the small plastic rings he uses at the top to guide water down into the compost and not into the sand.

Hard to argue with his results!!! You could pull just one carrot and make a meal of it for several people. I think I may build a few of these on the fence side of my new beds, pairing one of these with a 3x4' metal bed like what my others are.

I wonder if this would work with something like potatoes if you cored a wider hole but a shallower one?

Thoughts from those of you who grow carrots?

He is growing for size for a competition, so that seems to be a great technique for growing perfect, prize winning carrots. I remember seeing something from England about growing parsnips in drain pipes to produce roots that were 4 feet or more long.

Still, the sand may help you a lot. I garden in very heavy clay as well and I used dump compost to lighten my local soil, but I also grew varieties of carrots that were better adapted to my soil conditions, that is carrots that are short and fat rather then long and thin. We even grow round carrots in the community garden to discourage thieves. My garden buddy, Peggy, likes that variety for canning purposes. You can grow a lot of them in a small space, they are just a little bit more tedious to either peel or scrub up before eating them.

Ken's picture

Carrots and potatoes really do depend on good tilth. It's pretty annoying to try to peel lumpy, crooked root vegetables grown in chunky, lumpy, stony soil. However, I will tolerate a whole lot for the right flavor! I think that mixing your compost right into the sand would be easier in the containers. I have found that the bigger the container, the longer it holds water, so unless you have the time and attention to water multiple times per day in the dog days of summer, I suggest the biggest containers you can manage. I use 100 gallon galvanized horse troughs. The 100 gallon size is by far the most common size and typically less expensive than smaller or larger tanks. If you are cash strapped but have plenty of soil, you can make a pretty decent 'box' bed with 4 pallets. I do this for the compost heaps from the humanure toilet (that compost only goes on trees and the bamboo, not into garden beds, mostly because of concerns about persistent chemicals in human waste). I tie the pallets together with baling twine at the corners and the fill material really doesn't seem to fall out through the gaps very much at all.

In fact, I think the 'air pruning' would happen at those gaps to help keep the root systems centered in the bin. This would be an easy way to grow potatoes. I'd probably limit myself to three or four plants if they were not sprawling fingerling types, in which case I might only do one or two. Potatoes don't like to be crowded. Carrots though could be packed pretty tightly.

Organic carrots are so cheap that it's been hard to justify growing them myself. I realize they are 'factory-organic' but for the same amount of work I can get a lot more value from my tomatoes or potatoes.