User Guide

14
THE ROLE OF NUTRIENTS IN THE GROWTH AND
PRODUCTION OF PLANTS
The three primary macro elements needed by the plants are nitrogen
(N), phosphorus (P) and potassium (K), while calcium (Ca), magne-
sium (Mg) and Sulfer (S) are so called secondary macro elements. In
hydroponics, plants need a balanced nutritive solution, composed of
both primary and secondary elements.
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.
INTRODUCTION
NITROGENNITROGEN
NITROGENNITROGEN
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 • reduction in resistance to diseases and atmospheric agents
EFFECTS • increase of water demand (caused by an excessive
production of leaves)
• bad quality of fruits
• delayed ripening
• reduction in potassium absorption
47
SPECIFICATIONS
Range 10 to 100 mg/L
Resolution 2.0 mg/L
Accuracy ±15 mg/L ±7% of reading
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 93750
AA
AA
A-0 Potassium Reagent 6 drops
HI 93750
BB
BB
B-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 56.
MEASUREMENT PROCEDURE
Note: for sample preparation follow the NUTRIENTS SOLUTION (MR)
procedure at page 20.
• Select the program number 11 “Potassium MR” on the secondary
LCD by pressing PROGRAM M and L.
• 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.
10 mL
x 6
Potassium MR
POTASSIUM MEDIUM RANGE