Hydroponics Or Soilless Culture

Hydroponics Or Soilless Culture 

• The growing of plants with their roots in dilute solutions of mineral salts instead of soil led to increased understanding of plant nutrition. This cultivation of plants by placing the roots in nutrient solution is called hydroponics. Probably the first recorded use of soilless culture was by Woodward in 1699. 
• The method of growing plants in aqueous nutrient solutions as employed by Sachs and Knop is used experimentally and commercially today and known as hydroponic culture.
• The nutrient solution composition proposed by Knop (1865) and Arnon and Hoagland’s (1940) are commonly used.
• Arnon and Hoagland’s nutrient medium has the advantage, that it contains micro-nutrients also. Iron was added in the form of ferrous sulphate which often precipitated out. Now a days a chelating aent Na2-EDTA (disodium salt of ethylene diamine tetra acetic acid) is added.

Table : Some nutrient media

1. Knop’s solution (1865)

Salt Gm. per litre

KNO₃ 0.2

Ca(NO₃)₂ 0.8

KH₂PO₄ 0.2

FePO₄ 0.1

2. Shive’s solution (1915)

Salt Gm. per litre

Ca(NO₃).4H₂O 1.06

KH₂ PO₄ 0.31

MgSO₄.7H₂O 0.55

(NH₄)2SO₄ 0.09

FeSO₄.7H₂O 0.005

3. Hoagland’s solution (1929)

Salt Gm. per litre

Ca(NO₃)24H₂O 1.18

KNO₃ 0.51

KH₂PO₄ 0.14

MgSO₄.7H₂O 0.49

FeC₄H₂O₆ (Ferric tartrate) 0.005

H₃PO₃ (Phosphorous acid) 0.0029

MnCl₂.4H₂O 0.0018

ZnSO₄.7H₂O 0.00022

H2MoO₄.H₂O (Molybdic acid) 0.00002

CuSO₄.5H₂O 0.00008 

Fig. : Solution culture technique

•  In solution culture, plants are grown in pure nutrient media with only required elements. Glass containers are covered with black paper to protect the roots from direct light.
• Similarly, in other glass containers the plant is allowed to grow artificially with same nutritive culture which contains all essential elements except one, whose essentiality is to be judged.
• Such plants are compared with the controlled plant grown in balanced nutrient solution. If any change in characters appears, when compared with the normal plant, it is due to the deficiency of the particular element.

Uses of Hydroponics or soilless culture

•  The essentiality of mineral element.
•  The deficiency symptoms developed due to non-availability of particular nutrient.
• Toxicity to plant when element is present in excess.
• Possible interaction among different elements present in plant.
• The role of essential element in the metabolism of plant.