Hydroponics is the method of growing plants sans soil under controlled environment. Starting a hydroponic garden is not hard, as long as you plan and prepare for the task.
Your hydroponic plants will be more sensitive to nutrient levels and can't self-regulate themselves like soil-based plants so you will need to keep an eye on the proportion of hydroponics nutrients feed to your plants
Hydroponic gardening is a technique of growing plants without soil, plantation agriculture is an export oriented commercial tropical agricultural systems.
Hydroponics and other alternative methods can expand the possibilities of roof top gardening by reducing, for example, the need for soil or its tremendous weight.