Grape vines do not bear
Vines planted 2013 and have grown vigorously each year since, after which the vines are pruned about 1 foot from ground. Bought 1 each of white and red table grapes recommended for MD from Southern States. Second and third years had a handful of blossoms that never bore fruit. This year, no blossoms. They get a lot of sun and apparently have dropped roots near water table (we are in Eastport Annapolis, about 100 yards from Spa Creek). No evident pests. Soil perhaps? How to check?
Did you have your soil tested before you planted your vines? You might want to submit a soil sample for testing. That will give you a reading on the pH, nutrient content, and organic matter in your soil. With that information in hand, you will be able to identify if any soil amendments are needed. Take a look at our web page about soil testing and how to submit a sample. http://extension.umd.edu/hgic/soils/soil-testing
We recommend submitting a sample to any of the regional labs listed in this publication: http://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG110a_Soi...
When you submit your sample, indicate on your submission form that you are growing grapes. Some labs will provide specific recommendations on soil amendments if you indicate the crop you are growing.
Another possible factor in poor flowering/fruit set is weather. According to Penn State fruit specialists, "wet, cool or hot weather can result in poor fruit set and loose clusters. An extended period of low (<15°C/59°F) or high (> 32°C/ 90°F) temperature could interfere with the development of pollen and pistil during the flowering process or the development of the ovule after fertilization."
Here is additional information about causes of poor flower development and causes of poor fruit set in grapes.