Evaluation of Two Field Methods to Estimate Soil Organic Matter In Alberta Soils: Appendix 5 - Procedure for Basic EDTA Test

List of materials needed for basic EDTA test | Revised protocol for basic EDTA field method | Table of sites used for standards in basic EDTA test | Accuracy of the measuring scoop for procedure of Bowman (1997)

List of Materials Needed for Basic EDTA Test

EDTA disodium salt (4L)
Sodium hydroxide (2 x 1L)
Measuring cup (500 ml)
Label
Large plastic container
Scoop (1 ml aluminum measuring spoon)
Metal scoop to level off measuring spoon
Aluminum trays to dry samples
Mortar and pestle
Centrifuge tubes
Test tube holder for standards
Timer
Funnels
Filter paper
Felt marker
Graduated cylinder
Glass vials to place standards and unknown filtrates in

Revised Protocol for Basic EDTA Field Method

To prepare the Basic EDTA:

1.	Add 1 part EDTA disodium salt (0.05M) to 1 part Sodium hydroxide (0.25M) into a large container. Mix solution thoroughly using magnetic stirrer.
2.	Label the contents on the container.

To prepare the standards:

1.	Place each standard soil sample in mortar and pestle and crush.
2.	Take 0.5 g of sample and place in a centrifuge tube and label the cap with the site name.
3.	Using a graduated cylinder, add 20 ml of the basic EDTA to the tube. Cap and shake the tube for 30 seconds.
4.	Prepare a funnel by lining it with filter paper and place it in a clean centrifuge tube.
5.	Transfer the soil-basic EDTA solution to the funnel, making sure to pour slowly to ensure the solution does not seep over the filter paper.
6.	When filtrate has collected in tube, dispose of filter paper and clean the funnel. Transfer the filtrate to a glass vial, cap the vial and mark with the appropriate percent value of organic matter.
7.	Repeat steps 1-6 for soils corresponding to all standards, ensuring to wipe down the mortar and pestle after each use in order to avoid cross-contamination.

To prepare the samples for comparison to the standards the same procedure was followed as outlined above. We tested a maximum of 7 samples at one time, with 3 replicates for each sample, in order to process as many samples as possible. We set up 42 centrifuge tubes in test tube racks. Twenty millilitres of the basic EDTA was added to 21 of the tubes. The remaining 21 tubes were prepared by placing a funnel lined with filter paper in them. Using a 1 ml measuring scoop, 0.5 g of leveled soil from one of the samples was placed in a tube containing the basic EDTA solution. This was repeated two more times for this sample. The three tubes with the soil-basic EDTA mixture were then capped with lids labeled with the samples site and rep number (e.g. site 812 rep 1). They were shaken for 30 seconds and then each solution poured into three funnels lined with the filter paper. While these samples were filtering a new sample was prepared.

When all the filtrate had been collected for all 7 samples each filtrate was transferred to a glass vial, ensuring that the vial contained the same volume of filtrate as in the standard vials. The filtrate was compared to the standards and the estimated organic matter (%) recorded on a datasheet.

Table of Sites Used for Standards in Basic EDTA Test

Sites chosen to be standards and their corresponding organic matter values are presented in Table 6.

Table 6. Standard Soils and Corresponding OM (%) Lab Values.

.	.	.	Lab Values
Standard	Site Name	Site #	OM (%) 2001	OM (%) 2002	OM (%) 2003
0%	Blank	/	/	/	/
~1.5 %	Tilley	812	1.73	1.4	1.6
2%	Chinook	806	2.23	1.9	2.1
3%	Claresholm	793	3.8	3.4	3.3
4%	B.B. Mountain	594	4.15	3.6	3.8
6%	Beiseker	798	6.64	6.5	6.4
7%	Tomahawk	692	6.9	7	8
9%	Sexsmith	599	8.76	9.2	8.9
10%	Carstairs	746	9.96	11.6	10
12%	Wetaskiwin	727	12.43	12.8	12.5

Accuracy of the Measuring Scoop for Procedure of Bowman (1997)

We determined the accuracy of the measuring scoop for the Bowman (1997) method according to the following procedure:

1.	Take the scoop and place on scale, tare scale.
2.	Take scoop of dry soil and level.
3.	Place scoop with soil on scale and weigh, record the weight of the soil.
4.	Take soil that was in scoop and place in separate container.
5.	Repeat steps 1-4 four more times for the sample.
6.	After one sample has been weighed 5 times clean off the scoop and re-weigh the scoop and tare it again if needed.
7.	Proceed to the other samples repeating steps 1-6.

Results for the 11 soils used in this test indicate that on average the scoop measured 0.66 g of soil (Table 7).

Table 7. Results of Measuring Accuracy Test for Bowman (1997) Procedure.

.	Rep Number					Mean (g)	Range (g)	Variance	Standard Deviation	Coefficient of Variation
Sample I.D.	1	2	3	4	5	Mean (g)	Range (g)	Variance	Standard Deviation	Coefficient of Variation
Three Hills	0.68	0.72	0.67	0.65	0.64	0.67	0.08	0.001	0.03	4.63
Pincher Creek	0.6	0.58	0.67	0.58	0.57	0.60	0.10	0.002	0.04	6.77
Grimshaw	0.54	0.67	0.64	0.63	0.61	0.62	0.13	0.002	0.05	7.88
Oyen	0.71	0.68	0.67	0.81	0.69	0.71	0.14	0.003	0.06	7.97
Hanna	0.76	0.72	0.76	0.76	0.74	0.75	0.04	0.000	0.02	2.39
Wetaskiwin	0.6	0.53	0.5	0.55	0.59	0.55	0.10	0.002	0.04	7.51
Veteran	0.72	0.72	0.66	0.81	0.65	0.71	0.16	0.004	0.06	8.96
Carvel	0.55	0.62	0.75	0.65	0.73	0.66	0.20	0.007	0.08	12.40
Chinook	0.78	0.81	0.81	0.74	0.83	0.79	0.09	0.001	0.04	4.42
Lacombe	0.61	0.62	0.59	0.68	0.57	0.61	0.11	0.002	0.04	6.77
Carstairs	0.57	0.6	0.68	0.62	0.53	0.60	0.15	0.003	0.06	9.35
Overall Mean	.	.	.	.	.	0.66	.	.	.	.

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For more information about the content of this document, contact Len Kryzanowski.
This document is maintained by Laura Thygesen.
This information published to the web on May 5, 2004.
Last Reviewed/Revised on February 4, 2018.