[[Crops]] harvested from fertilized tiles have a chance to become [[Crops#Crop Quality|quality crops]] according to the following ratio: ≈33% Regular / ≈33% Silver / ≈33% Gold (assuming level 10 [[Farming]] skill).
Basic Fertilizer affects only the basic harvest, which means that extra crops gained at a single harvest ([[Potato|Potatoes]], [[Blueberry|Blueberries]], [[Cranberries]], etc.) will be regular quality.