If I were to add sand to the soil mix listed below, would it cause it to dry out too fast? It already dries out fast as is (it's been designed for absorption, so as not to create water logged plants, roots with wet feet, etc.). I don't want the sand to make it dry out MORE quickly.

If adding sand, how much?
1 batch makes 30 gallons

2-3 cubic feet pine bark fines (pine bark mulch)
5 gallons spaghnum peat moss
5 gallons perlite

2 c fertilzer (I use Osmocote; it's a pelleted dry fertilizer designed for container gardening)

2 c dolomitic lime

All my other veggies love this soil mixture. Unfortunately I've had problems with growing root veggies,with this soil mix.

I'm not saying there is anything wrong with it, root veggies just don't like it for some reason; they don't bulb...or form spindly roots not even big enough to eat.

I'm considering adding sand (normal, run-of-the-mill sand) to this mix. I'm NOT referring to sandy loam (sandy dirt) on the ground. I'd be adding sand to this soil less mix, in an attempt to mimic loam.

I've never tried the soil mix above with sand mixed in. I don't know if it will work. Will adding sand to the existing soil mix create a mix that root veggies like more?

This year I plan to use 4' x 12' raised beds.

W/fertility of soil, I use a time released fertilizer that is mixed into the soil mix listed above. It's a 19-6-12, and is Osmocote.

By sand, I mean like sand you'd find at the beach (not coarse sand). It doesn't have bits of rock or gravel in it either.

People have suggested adding compost to my mix. My concern with this, will adding the compost make the soil mix too heavy?

By heavy I mean it compacts. This is why you don't use normal dirt (from the ground) in containers; because it compacts and is too heavy.

My soil mix already has fertilizer in it. If I added compost to my soil less mix, then would it be overkill with fertilizing?

I ask this because I botched my soil mix last year by using wrong type of fertilizer; it was a variety that wasn't suitable for container gardening. I didn't realize I had done it till after I made my soil mix.

Had to dump and make new batch. Didn't have time or money to add correct fertilizer to the new batch. Tried to compensate by adding liquid fertilizer at the surface and this was a disaster....stressed out plants, way too much nitrogen in soil which attracted aphids, and a decimated harvest.

If I were to add compost to my soil mix, then would I reduce one of the amounts of the other ingredients in my soil mix. That is, would I reduce peat moss, and just add compost in its place for whatever amount was subtracted (i.e. I reduced the amount of peat from 5 gallons to 3, then I used 2 gallons of compost to make up the difference).

Or would I just mix in compost to my existing mix, without changing any of the measurements of the ingredients in the original mix at all. If so how much (in gallons, cups, etc.) compost should I add?

Here are the dimensions for my containers:

10 gallon:

Shape-rectangular; color-medium blue; type-plastic storage
container

Length-19" (1-1/2 feet plus the leftover 1 inch)
Width-13" (1 foot and 1 inch)
Depth-12" (1 foot)

18 gallon container:

Shape-rectangular; color-medium blue

Length:23"
Width: 17"
Depth: 15"

9-1/2 gallon container

Shape-rectangular; color-dark blue

Length: 19"
Width: 14-1/2" (1 foot, 2-1/2 inches)
Depth:11" (1 inch shy of a foot deep)

30 gallon

Shape-rectangular; color-gray

Length:28-1/2" (2 feet, 4 inches)

Width:19" (1-1/2 feet plus the additional leftover inch)
Depth: 17" (one inch short of 1-1/2 feet)

32 gallon

Shape-rectangular; color-gray

Length: 30-7/8" (2 feet, 6 inches)
Width:20" (1-1/2 feet plus the leftover 2 inches)
Depth: 17-1/2" (just shy of 1-1/2 feet)