Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Hydroponics and Plant Disease Management
Alok Shukla
Department of Plant Physiology, G.B.P.U.A&T., Pantnagar- 263 145 (UK)
Hydroponics is derived from a Greek word “hydros’’ meaning water and “ponos’’ meaning
labour i.e., working with water. It is soilless culture i.e., growing plants without soil. Several
civilizations have utilized hydroponic techniques and the records available reflected several
hundred years B.C as of Egyptian hieroglyphic records. Historical examples are “The hanging
gardens of Babylon and the floating gardens of the Aztecs of Mexico which describe the growing
of plants in water." Hydroponics is hardly a new method of growing plants.
William Frederick Gericke from the University of California, Berkeley campus has first
coined the term hydroponics in 1937.
Basic concept of Hydroponics
The main concept of hydroponics depends on criteria of essentiality given by Daniel Arnon and
Perry Stout in 1939 as
• Plant cannot complete a function and cannot complete its life cycle
• A deficiency can be corrected only by application of the specific element that is deficient
• The element plays a direct role in the metabolism
The essential elements are absorbed by the plant roots as inorganic ions. These elements
are characterized as macro and micro elements depending upon their requirements.
Generally if the element is required as less than 100 ppm it is classified as micro element
and if it is required as more than 100 ppm it is known as macro element. Besides
absorbing carbon, oxygen and hydrogen from the atmosphere and water all the other
elements are absorbed as ions of their respective elements as nitrogen as NH 4
+
, NO 3
-
phosphorus as HPO 4 2- , H 2 PO 4 - ,potassium as K + , calcium as Ca 2+ , magnesium as Mg 2+
,sulphur as SO 4 - , boron as H 3 BO 3 , BO 3 - , copper as Cu 2+ , iron as Fe 2+ , Fe 3+ , manganese
as Mn 2+ , zinc as Zn 2+ , molybdenum as MoO 4 - , chlorine as Cl - , cobalt as Co 2+
as Ni 2+
solution.
and nickel
ions. The common nutrient solution used for hydroponic culture is Hoagland
Composition of a modified Hoagland nutrient solution
Compound Conc. of stock Conc. of stock Element Final conc.
solution(mM) solution(g/L)
of element
(ppm)
Macronutrients
KNO 3
1000 101.10 N 224
Ca(NO 3
) 2 .4H 2
O 1000 236.16 K 235
NH 4
.H 2
PO 4
1000 115.08 Ca 160
MgSO 4
.7H 2
O 1000 246.49 P 62
S 32
Mg 24
- 141 -