Determination Of Nitrate And Nitrite; Determination Of Ammonium; Preparation Of Soil Extract B - MACHEREY-NAGEL VISOCOLOR Manual

Fill a test tube with ring mark (29) with soil extract A to a height
of approx. 3 cm, insert pH test strip in the sample. After 5 min,
remove the test strip and compare with the color scale, read off
pH value.
Note: For measurements with an electrometric pH meter, a
special soil extract A is prepared in the ratio 2 + 5, e.g. 20 g
soil + 50 mL extraction solution A. You may also use soil extract
AF (see 3.1, page 27).
pH-Fix 2.0–9.0
26

2.7 Determination of nitrate and nitrite

The nitrate / nitrite concentration is determined in soil extract A
®
using QUANTOFIX Nitrate / Nitrite test strips (23).
Procedure:
Dip the test strip in soil extract A for approx. 1 s. After 60 s, com-
pare the test field against the color scale. If nitrate or nitrite are
present, the test field turns pink.
The outer test field (at the end of the stick) indicates the nitrate
content, the inner test field indicates the nitrite content.
Please note: Reclose the package tightly immediately after use.
Do not touch the test fields with fingers.
Calculation of results:
Read off result of nitrate in mg/L NO
receive the result in mg/kg N.
e.g. 100 mg/L NO x 0.23 = 23.0 mg/kg N
3
Read off result of nitrite in mg/L NO
receive the result in mg/kg N.
Manual VISOCOLOR
Manual VISOCOLOR
5 mL
29
–
NO
3
–
NO
2
23
and multiply with 0.23 to
3
and multiply with 0.30 to
2
®
reagent case for soil analysis 02.19
®
reagent case for soil analysis

2.8 Determination of ammonium

The ammonium nitrogen content is determined in soil extract A
®
using QUANTOFIX Ammonium test strips (24).
+
NH
4
5 mL
24 29
Procedure:
Fill the test tube (29) with soil extract A up to the 5 mL mark. Add
+
10 drops of NH -1 (31) and swirl carefully. Dip the test strip in
4
the prepared test solution for 5 s. Compare test field with color
scale, read off measured value. If ammonium is present, the test
paper turns brown.
Close ammonium vial immediately after removing the test strip.
Do not touch the test field with fingers.
Calculation of results:
Read off result of ammonium in mg/L NH
to receive the result in mg/kg N.
e.g. 100 mg/L NH x 0.78 = 78 mg/kg N
4

2.9 Preparation of soil extract B

Soil extract B, which is prepared with extraction solution B (CAL
solution = calcium acetate lactate, 0.05 mol/dm
lyze phosphorus and potassium.
Preparation of the extraction solution:
Pour 100 mL of the CAL stock solution (27) into the bottle for
extraction solution B (3), add 0.4 L of distilled water (6) and mix
(or mix 2 x 100 mL CAL stock solution (refill) with 800 mL dist.
water).
Note: Should flocs or precipitates occur in the extraction solution
B, the solution is to be discarded. Rinse the bottle several times
with hot water and prepare fresh solution.
B
CAL
CAL
27 3
Preparation of the soil extract:
Normally, the soil should be dried at 105 °C for the purpose of re-
moving the soil water. However, since a drying oven will rarely be
available, it is sufficient to dry the soil overnight at room tempera-
+ +
NH -1 NH -1
4 4
31
and multiply with 0.78
4
3
), is used to ana-
Destilliertes
Wasser
Distilled water
Eau déstillée
Agua destilada
6 6
25