If you had two of the same plant (same genetics, same age) and planted one in soil and the other in a hydroponic system, the plant grown in soil will grow slower. This is why: When you are growing using the hydroponic method, you are using inert media. Because you are using inert media, you have full control over everything your plants consume. Basically you can create the perfect regiment to ensure your plant will flourish. Hydroponic Nutrients have been balanced to bring the right mixture of nutrients to your plant in a form that is easy for the plant to intake. Also, you have the ability to balance the pH to the perfect level to ensure the plant can easily metabolize the nutrients it consumes. One of the other reasons for the slower plant growth is that soil holds more water than typical inert hydroponic media. When growing with inert media, you will have to water more often. More watering equals more feedings. The more dry periods in the soil, the more root-oxygen stimulation. The plants consume more food and oxygen, you should see higher yields. Also, growing without soil can decrease the presence of natural pests/bugs because pest larva incubates in soil.