Question
Two years ago I started some garden boxes on my property.  I know I need to get the soil tested but have not done it yet.  The main problem, other than small veggies is this.  The raddish and carrots I plant grow nice greens but produce little or no root.  What type of soil imballance would cause this condition and what can I add to the soil to make it better for growing plants?  There is very little "local" soil in the boxes because of a high clay content.  It is mostly store bought top soil, garden soil, black cow, and a little compost.

Answer
Hi Victor, Clay is good.  Nothing is better for nutrient and water retention, but clay particles are very, very small, so in soils that are totally clay, the particles are packed tightly so you get poor root development unless it is loosened.  Farmers loosen clay by tilling each year and incorporating organic matter from last years crops into the soil.
The bagged soil products in your boxes are loose, but hold water and nutrients poorly.  I'd mix the soil in the boxes with the top 6-8" of clay.  Blend it well and you'll have better vegetables.  
I would get the soil tested.  Your pH should be around 6.5.
I'd also add 0-20-20 fertilizer, or an organic equivalent, to help your fruiting and rootcrop vegetables. Go light on the nitrogen.
Also watch your watering.  Elevated beds drain quickly, which is good unless they become too dry. Make sure you thoroughly moisten the root zone when you water.  Jim