Need advice on garlic

I have grown garlic for years with quite good success. I don't use seed garlic- I buy organic garlic. I have grown it in the same place, amending each year with steer manure and compost. My harvests for 2 years have been just average- I think I will use a new location this year. Question: Is the size of the harvested clove dependent upon the size that is planted? Or is the soil fertility more important? I appreciate any input--thanks- Jo in WA