Table of Contents

 1. Overview

Translated directly, hydroponics means plants working (growing) in water. The word hydroponic is derived from two Greek words: hydro – meaning water, and ponos – meaning labour.

A modern definition of hydroponics: A system where plants are grown in a growing media or substrate other than natural soil. All the nutrients (6 macro- and 6 micro-elements) are dissolved in the irrigation water and are supplied at a regular basis to plants. It is the cultivation of plants in nutrient-rich solution rather than in soil.

Hydroponics supplies the plant with what it needs, when it needs it. There is no genetic mutation that takes place inside the equipment nor are any mysterious wonder chemicals introduced to the plant roots.

In hydroponics, water is used much more efficiently than in soil cultivation. In certain hydroponic closed systems (recirculation) probably as much as 50% less water is used, while in open systems (drain to waste) 20-30% water savings can be realised. Hydroponics can be incredibly sophisticated and requires good management.

Hydroponics gives better and faster plant growth and potentially greater yields since the growth factors such as nutrients, temperature, humidity and light are closer to the plant’s exact needs. In some hydroponic environments you can grow the plants much more closely together than with conventional methods (provided there is sufficient light). This is because the plants do not make as large a root system as under conventional conditions since they don’t have to “go looking” for food. The food “comes” to them.

In South Africa, hydroponic vegetable production is almost always done under protection (e.g. tunnels covered in special plastic and shade-cloth).

Although “Undercover” is mostly seen as greenhouse and tunnel production, shade-cloth systems (where plants are grown mainly in soil but protected from harsh climate by the shade cloth) is also included in this category.

The difference between hydroponics vegetable production and production in soil:

Hydroponics Field production
No soil is required. Good topsoil is required. Good soil = good drainage, texture, organic material (e.g.compost), disease-free.
Nutrients are available at all times. Only water-soluble fertilisers are used. Hydroponics fertiliser formulations contain a balanced nutrient content, taking the plant species and growth stage, climate and water conditions into consideration.

 Nutrients must be added to soil. Unless a laboratory analysis is done, too much or too few nutrients can be added.

A great advantage with greenhouses is that since you can grow vegetables out of season when the prices are good. Vegetables can only be grown in season.
Soil borne diseases can be controlled. Soil borne diseases can build up in the soil.
Hydroponic production is not organic because artificial nutrients are always used and plants are never grown in soil. It is possible to produce organic vegetables in soil because one can use organic fertilisers such as compost and manure.

Advantages/disadvantages of Hydroponics vegetable production

Advantages Disadvantages
  • Hydroponically produced vegetables can be of high quality and need little washing.
  • Hydroponically produced crops tend to have a higher grade than conventionally produced crops in the open field.
  • Soil preparation and weeding is reduced or eliminated.
  • It is possible to produce very high yields of vegetables on a small area because an environment optimal for plant growth is created. All the nutrients and water that the plants need are available at all times.
  • Good soil is not a prerequisite to grow vegetables.
  • Water is used efficiently.
  • Pollution of soil with unused nutrients is greatly reduced.
  • Hydroponics production is management, capital and labour intensive.
  • A high level of expertise is required.
  • Daily attention is necessary.
  • Specially formulated, soluble nutrients must always be used.
  • If not monitored and controlled carefully, disease and insect populations can increase dramatically to cause great losses.
Source: Johannes Maree. Contact him at johannesmaree [at] absamail.co.za. 

Whereas hydroponics uses a liquid nutrient solution as a growing medium and aquaponics (see separate chapter) uses water and fish waste, aeroponics uses no growing medium at all. Plants are grown in the air or in mist. However, since nutrients are given to the plants through water, aeroponics can be considered  type of hydoponics.