Abstract: A majority of well-designed studies comparing nutrient density (milligrams of a given nutrient per kilogram of food) in organically and conventionally produced fruits and vegetables show modest to moderately higher concentrations of most nutrients in organic produce. Likewise, organic produce is either its flavorful as or more flavorful than conventional produce and often tends to store better. Physiological factors that may account for these differences include the levels and form of nitrogen applied to crops, the balance of macro- and micronutrients in the soil, soil quality, average cell size, glycosylation status, and concentrations of plant secondary metabolites.
Reference: Benbrook, Charles. (2009). The impacts of yield on nutritional quality: Lessons from organic farming. HortScience 44(1): 12-14.