To CLASS PAGE:
Lab #8 - 11/22/04
|a.) To follow
changes in nitrogen over time after
addition of ammonium (NH4+) on the three soils.
Extract iron (Fe) and manganese (Mn) from soils and soil fractions using the acidified oxalate method.
|II. Nitrification Procedure|
|1.) Weigh out
2.0 g (in duplicate) aliquots of your air-dried soil into two 30 mL
bottles. Add a clean stir bar.
|2.) Add 20 mL
of deionized water. Stir for 10 minutes. Pull a 2 mL blank
suspension sample while
stirring and record initial pH.
|3.) From a
0.1 M NH4Cl stock solution, add the calculated amount of
achieve an initial NH4+ of 1 mM without changing the solid:solution ratio. The “time zero” will
coincide with the emptying of the pipette carrying the NH4+ stock solution.
will be shaken on the Big Bill shaker and 2 mL suspension samples
removed at 1h, 2h,
24h, 48h, 96h, and 168h (one week).
equilibrium pH using a calibrated pH meter during sampling.
reaction between NH4+
and soil will be stopped by filtration with 0.2µm
pore size membrane
filters using 25 mm filter holders and 10 mL syringes into labeled test tubes.
filtrates in labeled test tubes in the refrigerator. The
concentrations of NH4+, NO3-,
NO2- will be measured in the filtrates using colorimetic methods.
|III. Fe and Mn Extractions (McKeague and Day, 1966).|
Weigh out 0.50 g (in duplicate) aliquots of your air-dried soil and
0.10 g aliquots of each fraction
(feel free to readjust this weight depending on the amount of fraction remaining) in 40 mL
centrifuge tubes (this should be a total of 8 tubes per group).
Add 10 mL of 0.2 M (NH4)2C2O4
buffered to pH 4.0.
Wrap in aluminum foil and shake for 24 h.
Separate the solid from solution by centrifugation and/or filtration.
Total Fe and Mn will be measured using FAAS.
|| McKeague, J.A. and J.H. Day.
1966. Dithionite and oxalate-extractable Fe and Al as aids in
differentiating various classes of soils. Can. J. Soil Sci.