Analyses are performed in different ways. Methods basically serve as guidelines. In
some cases, they must be modified and adapted to the conditions of each laboratory or
individual experiment.
The elements extracted from the soil during chemical analysis are referred to as
"available nutrients" and are important in determining soil fertility.
| Parameter |
Method |
Observations |
| pH |
Potentiometric |
Soil:water 1:2
Soil: KCl (1N) 1:2 |
| Moisture (%) |
Gravimetric |
Loss of moisture at 105 °C |
| Conductivity (EC) |
Potentiometric |
Estimation of soil salinity |
| Texture |
Densimetric |
Hidrometer (Bouyucos) |
Organic carbon
in Soils (organic matter, %) |
Volumetric
Molecular spectrometry (Autoanalyser)
|
Walkey-Black (Nelson-Sommers) Dicromate-sulfuric acid
oxidation |
| Phosphorus (P) |
Molecular spectrometry (Autoanalyser)
(Murphy-Riley) |
Bray I or II (diluted fluoride) Olsen (sodium bicarbonate)
|
| Exchangeable cations (pH<5.5) Al
K
Ca, Mg |
Volumetric
Atomic emission spectrometry
Atomic absorption spectrometry |
Al, Ca, and Mg in KCl 1N
K in diluted fluoride(Bray II)
NaOH 0.05M |
| Effective cation exchange capacity (ECEC) |
|
ECEC = Al + Ca + Mg + K |
| Aluminum saturation (%) |
|
Al/ECEC * 100 |
| Exchangeable cations (pH>5.5) K, Na
Ca, Mg |
Atomic emission spetrometry
Atomic absorption spetrometry |
Ca, Mg, K, and Na in
1N NH4-Acetate
(Thomas, 1982)
|
| Cation exchange capacity (CEC) |
Volumetry
(NaOH 0.1N) |
In ammonium acetate 1N |
Micronutrients
(Cu, Zn, Mn, Fe) |
Atomic absorption spectrometry |
Double acid extraction
(Martens and Lindsay, 1990) |
| Sulfur (S) |
Turbidimetric |
Calcium phosphate extraction
(Wall et al., 1980) |
| Boron (B) |
Molecular spectrometry
(manual) |
Hot water extraction
(Mahler et al., 1984) |
| Molybdenum (Mo) |
Graphite furnace spectrometry |
Acid ammonium oxalate extraction
(Kubota and Cary, 1982) |
| Total nitrogen (N) |
Molecular spectrometry
(Autoanalyser) |
Sulfuric-salicilic digestion |
| Ammonium nitrate |
Molecular spectrometry (Autoanalyser) |
KCl 1M extraction |
The ASL conducts the
following analyses: 