14
THE ROLE OF NUTRIENTS IN THE GROWTH AND
PRODUCTION OF PLANTS
The three elements that are mostly needed by the plants are nitrogen
(N), phosphorus (P) and potassium (K). They are called the macronu-
trients while other elements, needed by plants in smaller amounts, are
called microelements. In hydroponics, plants need a balanced nutritive
solution, composed of macro and microelements.
Shortage or excess of even only one nutritive element may cause an
imbalance in plant physiology and in the absorption of the other
nutrients. Nutrients shortages may result in irregular plant growth, low
resistance to diseases, scarce production both in quantity and quality,
while nutrients excess may cause waste of fertilizer, pollution of the
groundwater and the possible accumulation of dangerous substances
in the crops produced.
NITROGEN
Nitrogen (N) is mostly absorbed by plants as nitrates (NO
3
-
) and, in
smaller amount, in the form of ammonium (NH
4
+
). In hydroponics, an
adequate ratio between the two forms is generally used in nutritive
solutions.
PRESENT IN
proteins, enzymes, chlorophyll, hormones, vitamins,
DNA and RNA
ACTION
• is fundamental for plants in phase of growth
• promotes the lengthening of trunks and sprouts
• increases the production of foliage
• helps to absorb other nutrients
(in particular phosphorus)
• assists a bigger production for both size and
number of fruits
SHORTAGE
• slower growth
EFFECTS
• smaller leaves
• yellowing of leaves
• smaller fruits
• premature ripening
EXCESS EFFECTS
• reduction in resistance to diseases and atmo-
spheric agents
• increase of water demand (caused by an excessive
production of leaves)
• bad quality of fruits
• delayed ripening
• reduction in potassium absorption
INTRODUCTION
39
SPECIFICATIONS
Range
0.0 to 20.0 mg/L
Resolution
0.5 mg/L
Accuracy
±3.0 mg/L ±7% of reading
Typical EMC
±0.5 mg/L
Deviation
Light Source
Tungsten lamp with narrow band interference
filter @ 610 nm
Method
Adaptation of the Turbidimetric Tetraphenylborate
method. The reaction between Potassium and
reagents causes turbidity in the sample.
REQUIRED REAGENTS
Code
Description
Quantity
HI 93750AAAAA-0
Potassium Reagent
6 drops
HI 93750BBBBB-0
Powder Reagent
1 packet
REAGENT SETS
HI 93750-01
Reagents for 100 tests
HI 93750-03
Reagents for 300 tests
For other accessories see page 48.
MEASUREMENT PROCEDURE
Note: for sample preparation follow the IRRIGATION WATER (LR)
procedure at page 17.
• Select the program number corresponding to Potassium LR on the
secondary LCD by pressing PROGRAM
t
and
s
.
• Fill the cuvet with 10 mL of sample, up to the
mark.
• Add six drops of HI 93750A,
replace the cap and swirl the
solution.
• Place the cuvet into the holder and
ensure that the notch on the cap is
positioned securely into the groove.
1
0
m
L
x
6
Potassium LR
POTASSIUM LOW RANGE
