I would just add soil - plain old garden soil, topsoil, even clean fill. There is no mineral component to your soil mix so you are lacking in most trace elements. Adding "dirt" should even things out to some degree but I'd not be very concerned about the N levels anyway - they won't maintain at that level very long :-)

I'd be a bit more concerned about the low levels of P - hard to imagine that the case with much animal manure involved. But inadequate concentrations of phosphorus would cause more issues with plant growth and flower/fruit production than any overabundance of N. I'd monitor this closely.

1. The cheap home soil test kits are not reliable. That said, with that mix I would surely expect a very high N level.

2. Your mix looks a lot like the "Mel's Mix" that SFG folks favor, but using perlite instead of vermiculite and subbing in composted manure for a portion of the compost. You may get some good feedback or advice in the SFG forum. Those who use it tend to love it.

3. It is what it is, and you probably can't change it simply or easily. I'd plant and grow and see what happens. Enjoy now, worry later.

Link to the SFG forum below:

Here is a link that might be useful: Square Foot Gardening Forum

This post was edited by TXEB on Tue, May 21, 13 at 21:27

Thanks for the advice from both of you.

I should also mention that I have about 150 onions (Sets) that were originally planted inside and went out into the raised beds roughly 3 weeks ago now; except for a couple that withered almost immediately they've been doing fine. I also have Beets, Radish, Garlic and Carrots coming up...

I'm beginning to wonder if this is just a good indication that the soil test kit isn't very accurate.

Only time will tell I suppose.