Hello...I am totally new to the website...I hope
someone has some advice for me. My garden has been VERY non-productive the last few years in
spite of the fact that I am using fertilizer.
I have noticed that the soil is full of small
black ants as I am planting the starter plants.
Is it possible that these ants are feeding on the
roots of the plants and stunting their growth
and productivity? If so, what can I use to get
rid of them? Any help is appreciated!!!

Ants are not generally a problem for plants. They may have secondary effects but no, i reckon your problem is not ants.
However, they don't like moist soil, so i suggest the garden is too dry and may not have any water retension capability. Fertilizer does not improve soil. It simply adds plant food. It does not create the medium for those plants to use that food. Organic matter makes good soil, so for a more productive garden, add lots of compost and other organic matter.