GEOLOGICAL SURVEY CIRCULAR 841 

Four Reference Soil and 

Rock Samples for Measuring 

·Element Availability in the 

Western Energy Regions 

Four Reference Soil and 

Rock Samples for Measuring 

Element Availability in the 

Western Energy Regions 

By J. G. Crock and R. C. Severson 

GEOLOGICAL SURVEY CIRCULAR 841 

1980 
United States Department of the Interior 

CECIL D. A~DRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Any use of trade names is for descriptive purposes only and does not imply endorsement by the 

U.S. Geological Survey. 

Free on application to the Branch of Distribution, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page 

Abstract • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I 

Introduction ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• • •• • • • • • • • • • I 

Acknowledgments •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• • • • • I 

Sample Descriptions • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I 

Sample Preparation • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 

Laboratory Methods • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 

Total Element Content • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 

DTPA-Extractable Metals • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3 

Cation Exchange Capacity and Exchangeable Cations.......................................... 3 

Water-Saturation Extract.................................................................. 5 

Hot-Water-Soluble Boron •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• •... 6 

Soil pH ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• • • • • • 7 

Error Due to Sample Splitting.................................................................... 7 

Error Due to Laboratory Analysis • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I3 

Sampling-Homogeneity Estimates • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • IS 

References •••••••••••.•••••••••••••••••••••••••••••••••••••••••••••••••••••.••••••••••••••• • • • • I6 

Figure 

Table 

ILLUSTRATIONS 

Page 

1. Frequency distribution of total Cu in Sample A • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 7 

2.. Frequency distribution of DTPA-extractable Fe in Sample-A.............................. 8 

1. 

2.. 

3. 

4. 

s. 

6. 

7. 

8. 

9. 

10. 

11. 

12.. 

13. 

TABLES 

Page 

Preparation of standard solutions and instrumental settings 

for determining DTP A-extractable metals • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3 

Instrumental parameters for the determination of Ca, K, Mg, 

Na, and Cation Exchange Capacity • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 4 

Preparation of standard solutions for C.E.C. measurements 

and for measurements of exchangeable Ca, K, Mg, and Na • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 5 

Preparation of standard solutions and pump arrangements for 

determining cations in a water-saturation extract • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 6 

Unbalanced, nested, analysis-of-variance design used to 

estimate splitting and laboratory errors • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 8 

Variance components for splitting and analyses of Sample A............................... 9 

Variance components for splitting and analyses of Sample B. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • IO 

Variance components for splitting and analyses of Sample C............................... 11 

Variance components for splitting and analyses of SampleD ••••••••••••••••••••••••••••••• I2 

Summary statistics from repeated analyses of Sample A • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I3 

Summary statistics from repeated analyses of Sample B • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I3 

Summary statistics from repeated analyses of Sample C • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I4 

Summary statistics from repeated analyses of Sample D • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • I4 

III 

Four Reference Soil and Rock Samples 

for Measuring Element Availability 

in the Western Energy Regions 

By J. G. Crock and R. C. Severson 

ABSTRACT 

Attaining acceptable precision in extractable 

element determinations is more difficult than in total 

element determinations. In total element 

determinations, dissolution of the sample is 

qualitatively checked by the clarity of the solution and 

the absence of residues. These criteria cannot be used 

for extracts. Possibilities for error are introduced in 

virtually every step in soil extractions. Therefore, the 

use of reference materials whose homogeneity and 

element content are reasonably well known is essential 

for determination of extractable elements. In this 

report, estimates of homogeneity and element content 

are presented for four reference samples. Bulk 

samples of about 100 kilograms of each sample were 

ground to pass an 80-mesh sieve. The samples were 

homogenized and split using a Jones-type splitter. 

Fourteen splits of each reference sample were 

analyzed for total content of Ca, Co, Cu, Fe, K, Mg, 

Mn, Na, and Zn; DTPA-extractable Cd, Co, Cu, Fe, 

Mn, Ni, Pb, and Zn; exchangeable Ca, Mg, K, and Na; 

cation exchange capacity; water-saturationextractable Ca, Mg, K, Na, Cl, and so4; soil pH; and 

hot-water-extractable boron. Error measured between 

splits was small, indicating that the samples were 

homogenized adequately and that the laboratory 

procedure provided reproducible results. 

INTRODUCTION 

Measures of extractable or "available" elements 

in soils have historically been more useful for 

estimating plant element composition than measures 

of total element content (Bear, 1964). At the present 

time, there is much concern for monitoring and 

predicting changes in the natural soil-plant 

environment resulting from energy-related 

developments (for example, Wali, 1979; Schaller and 

Sutton, 1978). Measures of extractable elements in 

soils are preferred to measures of total element 

content for such evaluations; however, many different 

extraction techniques have been used for a single 

element (for example, Andersson, 1975). Therefore, in 

selecting methods to use in performing such analyses, 

we considered those that would possibly be used by 

regulatory agencies to write guidelines and those that 

appear to have the greatest potential for providing an 

estimate of element utilization by plants in the West. 

The methods are taken from the literature and are 

ones currently in use and generally accepted (Black, 

1965; Sandoval and Power, 1977; Lindsay and Norvell, 

1969, 1978). However, some of the steps in sample 

preparation and analysis have been modified to 

increase efficiency and reduce operator error. 

Because many variables exist in sample preparation, 

extraction, and analysis that affect the actual amount 

of an element extracted (for example; Jacober and 

Sandoval, 1971; Severson and others, 1979; and 

Soltanpour and others, 1976), reference samples have 

been prepared to determine the precision of analyses 

made using these laboratory procedures. This report 

discusses the preparation of four such reference 

materials and describes the samples, the analytical 

procedures, and the results of repeated analysis. 

ACKNOWLEDGMENTS 

The authors acknowledge the support of T. K. 

Hinkley and L. P. Gough, both with the U.S. Geological 

Survey, for assistance in collecting the bulk samples. 

J. M. MeN eal, J. J. Dickson, K. C. Stewart, R. E. 

McGregor, T. Law, V. Merritt, and C. Gent, also with 

the U.S. Geological Survey, assisted in sample 

preparation and analysis. R. Dinkmeyer, Colorado 

School of Mines Research Institute, was most 

cooperative in providing the use of space and 

equipment for splitting and homogenizing the bulk 

samples. Finally, we are grateful to the management 

of the Decker Coal Company for providing access and 

assistance in collecting materials from the headwall of 

their mine near Decker, Mont. 

SAMPLE DESCR1P'I10NS 

Four reference samples are described in this 

report. Two of the samples are of Tertiary rocks: one 

from a roadcut in New Mexico (Sample A), and the 

other from the headwall of the Decker Coal Mine 

(Sample B), operated by the Decker Coal Company and 

the State of Montana. The other two samples are soils 

from the San Juan Basin of New Mexico (Sample C and 

Sample D). 
Sample A consists of a buff-colored, clayey 

siltstone of Tertiary age (formation unknown), 

collected from a roadcut in San Juan County, N. Mex. 

The approximate sampling location was in sec. 9, T. 23 

N., R. 8 W. (about lat 36, 15' N. and long 107 ,40' W). 

Sample B consists of a gray, massive sandy 

siltstone of Tertiary age (formation unknown), 

collected from the headwall of the Decker Mine. The 

sample was collected about 21 m stratigraphically 

above the coal, on the lower part of the upper 

overburden bench. The mine is located in sees. 15, 16, 

T. 95 S., R. 40 E., Bighorn County, Mont. (about lat 

45 ,08' N. and long 106 ,49' W). 

Sample C consists of the A1 horizon (sampled 

between the depths of 5 and 50 em) of a soil classified 

at the series level as Manzano (Cumulic Haplustoll, 

fine-loamy, mixed, mesic). The sample was collected 

from McKinley County, N. Mex., from sec. 22, T. 20 

N., R. 5 W. (about lat 35, 57'35" N. and long 107,21 '10" 

W). 

Sample D consists of the B2 horizon (sampled 

between the depths of 20 and 45 em) of a soil 

classified at the series level as Doak (Typic Haplargid, 

fine-loamy, mixed, mesic). The sample was collected 

in San Juan County, N. Mex., from sec. 32, T. 23 N., R. 

8 W. (about lat 36,21'15" N. and long 107,50'10" W). 

SAMPLE PREPARATION 

The samples were homogenized in the following 

sequence: The rock samples were initially crushed to 

less than 5 mm in diameter by passing them through a 

motor-driven jaw crusher. The soil samples did not 

require this treatment. After initially crushing the 

rock samples, all four samples were treated similarly. 

Each sample was mixed by successive passes through a 

large-capacity Jones-type splitter. A single pass was 

not used: opposite quarters of samples already split 

were recombined and resplit. Splitting and 

recombining were repeated several times to assure 

adequate homogenization. The 100-kg samples were 

then split into 16 parts and stored in gallon cartons. 

Each of the 16 gallons of material obtained from the 

splitting was further ground in a ceramic mill to pass 

an 80-mesh sieve. The 16 gallons of finely ground 

material were then recombined and split again using 

the quartering and recombining procedure described 

above. Each resulting gallon (or partial gallon) of 

sample was further split into eight parts by again 

following the same procedure of quartering and 

recombining opposite quarters; however, a much 

smaller Jones-type splitter was used. Each of the 

eight subsamples was labeled to indicate its splitting 

history. A total of 128 splits was obtained for each 

reference sample, each split containing about 500 g of 

material. 

LABORATORY METHODS 

Total Element Content 

The sample is totally dissolved using a lowtemperature, low-pressure, multi-acid digestion 

procedure modified from that described by Swanson 

and Huffman (1976). In this procedure the sample is 

digested in a mixture of concentrated hydrofluoric, 

2 

nitric, and perchloric acids in a platinum dish on a 

hotplate. After evaporating to dryness, the remaining 

salts are dissolved in 5 percent hydrochloric acid and 

brought to a given volume. Flame atomic absorption 

spectrometry (A.A.S.) is used to determine the total 

element content of the resulting solution. 

Procedure: 

1) Weigh 1.000 g of the air-dried soil into a 

100-mL, flat-bottomed, platinum Blair-form 

dish. Wet the sample with a minimal 

amount of demineralized water. 

2) Add 10 mL concentrated nitric acid, 10 mL 

of concentrated perchloric acid, and 10 mL 

of concentrated (42 percent) hydrofluoric 

acid. 

3) Cover with a teflon watch glass and let 

stand overnight in a well-ventilated hood. 

4) Place the covered dish on a steam bath and 

heat for 1 hour. 

5) Place on a hotplate pre-set to about 110 , C 

and remove the teflon cover. Heat gently 

until fumes of perchloric acid are visible. 

Slowly bring the temperature to about 

200, C over a time period of 2 hours. 

Evaporate to dryness. 

6) Cool. Wet the salts with about 10 mL of 

demineralized water. Add 5 mL of 

perchloric acid, swirling to mix. Repeat 

step 5. 

7) Cool and add 25 mL of demineralized water, 

5 mL of concentrated hydrochloric acid, and 

about 1 mL of 30 percent hydrogen peroxide. 

8) Cover with a glass watch glass. Return to 

the steam bath for about 30 minutes to 

insure that all of the salts are dissolved and 

that the excess peroxide is destroyed. 

9) Cool and bring to volume in a 100-mL 

volumetric flask using demineralized water. 

Analysis: 

All elements were determined using a PerkinElmer 5000 A.A. spectrophotometer or a Perkin-Elmer 

603 A.A. spectrophotometer. Cobalt was first 

extracted into methyl-iso-butyl ketone (Mountjoy, 

1970). Zinc, copper, and manganese were determined 

directly, whereas calcium, magnesium, potassium, and 

sodium were determined by on-line dilutions using a 

peristaltic pump with an appropriate diluent. The 

sample and diluent tubes are connected before the 

nebulizer by a small glass "h" interface. The diluent 

tube is usually connected to the top, straight section, 

because the pump tube is usually of larger radius and 

its flow remains unbroken in the introduction of 

sample. 

Notes: 

1) 

2) 

Digestion can easily be done in 150-mL 

teflon beakers. 

The digestion and evaporation steps are 

slower because care must be taken not to 

overheat and melt the beakers. 

The addition of the hydrogen peroxide is 

important to insure complete dissolution of 

the manganese oxides that may form if 

appreciable manganese is present. 
DTPA-Extractable Metals 

The DTP A (diethylene triamine pentaacetic acid) 

extraction procedure has been modified from Lindsay 

and Norvell (1969, 1978). The extracting solution is 

0.005 M DTPA, 0.01 M calcium chloride, and 0.1 M 

triethanolamine at a pH of 7 .30. 

Solution: 

1) To a Z-L volumetric flask, add 3.9335 g 

DTPA, 3.90 g calcium chloride, and 29.84 g 

triethanolamine. (See Note 3.) Bring to 

about 1950 mL using demineralized water. 

Mix well and adjust the pH to 7.30 using 

concentrated ammonium hydroxide or 

concentrated nitric acid. Bring to volume 

using demineralized water. 

Procedure: 

Weigh 15.00 g of air-dried soil into a 125-mL 

polyethylene Erlenmeyer flask. Add 30.0 mL of the 

DTPA solution. Cap tightly with a polyethylene 

thimble. Shake on a reciprocating shaker at 240 

cycles/minute for Z hours. Decant into a 5Q-mL 

polyethylene centrifuge tube, and centrifuge for 5-6 

minutes at ZOOO rpm. Decant and filter through an 11-

cm Whatman 41 filter paper into a Z-oz polyethylene 

bottle. Acidify with four drops of concentrated nitric 

acid. 

Analysis: 

Eight metals are determined from this sample 

preparation: Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn. A 

Perkin-Elmer 5000 A.A. spectrophotometer 'and a 

Perkin-Elmer AS50 auto-sampler with peristaltic pump 

for on-line dilutions were used for all analyses. 

Instrument settings, pump-tube sizes, and standard 

preparations are given in table 1. 

Table !.--Preparation of standard solutions and instrumental settings for 

determining DTPA-extractable metals 

[Dilute to volume using the DTPA reagent solution, N.A., not applicable] 

Standard solutions1 Flow Wavelength Slit 

Metal Sl 52 53 rates (nm) (nm) (mL/min) 

Fe 2.0 5.0 10.0 22.6 248.3 0.2 31.0 

Mn 2.0 5.0 10.0 22.6 

31.0 

279.5 .2 

Zn 1.0 2.0 5.0 22.6 213.9 .7 

31.0 

Cu 1.0 2.0 5.0 N.A. 324.7 .7 

Co 1.0 2.0 0 N.A. 240.7 .2 

Ni 1.0 2.0 0 N.A. 232.0 .7 

Pb 1.0 2.0 0 N.A. 4283.3 • 7 

Cd 1.0 2.0 0 N.A. 4228.8 .7 

1All metal concentrations in parts per million (ppm). 2sample. 

3oemineralized water. 

4wtth background correction. 

Notes: 

1) All the variables in this extraction will 

affect the amount of metal extracted. Care 

must be taken to follow the procedure exactly to obtain precise data. A good 

description of the effect of the variables is 

given by Soltanpour and others (1976) and 

Severson and others (1979). 

3 

Z) Compressed air was blown over the motor of 

the reciprocating shaker to prevent 

overheating and to maintain the DTPA 

solution at room temperature. 

3) Use a 50-mL beaker when weighing the 

triethanolamine. 

4) Extraction of the DTPA solution might be 

necessary if low-level measurements of Co, 

Ni, and Pb are required. Initial 

investigations have shown that the DTP A 

complex will have to be destroyed before 

successful extraction/ concentration can be 

done. Elimination of as many major 

elements as possible is essential in order to 

use flameless A.A.S. to determine low-level 

Co, Ni, and Pb (Govett and Whitehead 

(1973), Mubarak and others (1978), and 

Yamasaki and others (1975)). 

5) Soltanpour and Schwab (1977) have reported 

success with a new extracting solution for 

both micronutrents and macronutrients of 

soils. They use a 0.005 M DTPA and 1.0 M 

ammonium bicarbonate (NH4HC03) solution 

at a pH of 7 .6. The results are reported to 

correlate well with the DTPA extraction 

procedure. 

Cation Exchange Capacity and 

Exchangeable Cations 

In this extraction, the readily soluble and readily 

exchangeable cations are measured. The major cations 

determined are Ca, K, Mg, and Na. The extraction 

procedure used has been modified from that of 

Chapman (1965). Atomic absorption spectrometry 

with on-line dilution is the method of analysis for all 

determinations. 

Solutions Needed: 

1) 100 meq Ca/L: Weigh 5.004 g calcium 

carbonate (primary standard grade) into a 

1.00-L volumetric flask. Add about 100 mL 

of demineralized water. Add dropwise a 

minimum amount of concentrated 

hydrochloric acid until the solid is 

dissolved. Then add 10 mL in excess. Dilute 

to volume. 

Z) 100 meq Na/L: Weigh 5.844 g sodium 

chloride (primary standard grade) into a 

1.00-L volumetric flask. Dissolve and dilute 

to volume with demineralized water. 

3) 100 meq K/L: Weigh 7.455 g potassium 

chloride into a 1.00-L flask. Dissolve and 

dilute to volume with demineralized water. 

4) 100 meq Mg/L: Dissolve 1.216 g magnesium 

metal ribbon in a minimum of 50 percent 

hydrochloric acid in a 1.00-L volumetric 

flask. Dilute to volume with 1 percent 

hydrochloric acid. 

5) 5 percent lanthanum buffer: Weigh 234.4 g 

reagent grade lanthanum oxide (La2o3) into 

a large beaker (Z Lor larger). Wet the solid 

with about ZOO mL demineralized water. 

Place the beaker in an ice bath in a hood. 

Add very slowly a total of 500 mL 

concentrated hydrochloric acid while 
stirring constantly with a glass rod. When 

addition of the acid has caused complete 

dissolution, dilute to 4.00 L with 

demineralized water. (See Note 1.) 

6) 0.1 percent Na buffer: Dissolve 2.542 g of 

sodium chloride in 1.00 L of demineralized 

water. 

7) 0.1 percent K buffer: Dissolve 1.907 g of 

potassium chloride in 1.00 L of 

demineralized water. 

8) 1.0 N sodium acetate: Dissolve 136 g 

sodium acetate trihydrate in water to just 

less than volume in a 1.00-L volumetric 

flask. Adjust the pH to 8. 2 with acetic acid 

or sodium hydroxide. Dilute to volume with 

demineralized water. 

9) 1.0 N ammonium acetate: Dilute 114 mL of 

glacial acetic acid with demineralized water 

to about 1 L in a 2.00-L volumetric flask. 

Slowly add 138 mL of concentrated 

ammonium hydroxide. Dilute with 

demineralized water to about 1980 mL. 

Adjust the pH to 7 with concentrated acetic 

acid or concentrated ammonium hydroxide. 

Dilute to a 2-L volume with demineralized 

water. 

10) Isopropyl alcohol 99 percent, reagent grade. 

11) 0.1 percent sodium hexametaphosphate: 

Weigh 0.50 g sodium hexametaphosphate, 

(NaP03)6, into a 500-mL volumetric flask. 

Dissolve and dilute to volume with 

demineralized water. 

rocedure: 

1) Weigh 4.00 g of air-dried soil into a 65-mL 

culture tube (20 mm X 225 mm). Add 33 mL 

of 1.0 N ammonium acetate solution. Place 

the tube horizontally on a reciprocating 

shaker and shake for 3 minutes at 240 cycles 

per minute. Centrifuge at 2000 rpm for 5 

minutes. (See Note 2.) Decant the solution 

through a 6.5-cm funnel containing 11-cm 

Whatman 41 filter paper into a 100-mL 

volumetric flask. Repeat the ammonium 

acetate wash procedure two additional 

times, making sure that the soil plug is 

broken up before using the reciprocating 

shaker. Add four drops of the 0.1 percent 

sodium he~ametaphosphate solution. Bring 

to volume with 1.0 N ammonium acetate. 

This solution will be analyzed for 

exchangeable Ca, Mg, Na, and K. The 

amount of sodium added as the 

hexametaphosphate is negligible when 

compared to the sodium present as 

exchangeable sodium. 

2) To the residual soil-plug residue, add 25 mL 

of 1.0 N sodium acetate solution. Break up 

the plug and shake on the reciprocating 

shaker for 3 minutes at 240 cycles per 

minute; centrifuge at 2000 rpm for 5 

minutes; decant and discard the solution. 

Repeat Step 2 three additional times. 

3) To the soil plug from Step 2, add 20 mL of 

isopropanol. Break up the plug; shake on the 

reciprocating shaker for 3 minutes at 240 

cycles per minute; centrifuge at 2000 rpm 

for 5 minutes; decant and discard the 

solution. Repeat Step 3 three additional 

times. 

4) To the above soil plug, add 33 mL of 1.0 N 

ammonium acetate solution. Break up the 

plug and then shake on the reciprocating 

shaker for 3 minutes at 240 cycles/minute. 

Decant and filter through 11-cm Whatman 

41 filter paper into a 100-mL volumetric 

flask. Repeat Step 4 two additional times, 

combining the washes. Bring to volume with 

the ammonium acetate solution. This 

solution will be analyzed for Na as a 

measure of total cation exchange capacity 

(C.E.C.) of the soil. 

Analysis: 

A Perkin-Elmer 5000 A.A. spectrophotometer 

and a Perkin-Elmer As-SO autosampler were used for 

automated, sequential A.A.S. analysis of all five 

elements. On-line dilution of the samples using a 

peristaltic pump and rotation of the burner head allows 

for direct measurement of all five elements. (See 

Notes 3-5.) 

Consult table 2 for preparation of the standards 

used for determining Ca, Mg, K, and Na in the first 

solution. The standards for determining total C.E.C. 

as Na are made by pipetting 7.5 mL, 12.5 mL, and 25.0 

mL of the stock Na solution into a 100 mL volumetric 

flask and diluting to volume with ammonium acetate. 

This results in solutions of 7 .5, 12.5, and 25.0 meq/L, 

respectively. 

Table 3 lists the instrumental conditions. All 

elements were determined using the 10-cm single-slot 

burner. Three 3-second integrations were taken in the 

concentration mode and automatically averaged. 

There is a multiplication factor of 2.5 if the 

results are reported as meq/100 g. 

Notes: 

1) 

2) 

3) 

When preparing the lanthanum buffer, the 

operator should wear rubber gloves and eye 

protection. 

A slightly longer centrifuging time, as much 

as 10 minutes, might be required for the 

clay-rich soils. 

If the peristaltic pump and burner rotation 

are not employed to effect the proper 

dilution of the samples, then dilute the 

samples for exchangeable Ca, Mg, Na, and K 

with appropriate buffer to give a 1:50 

dilution. For the total C.E.C. measurement, 

at least a 1:100 dilution should be made. 

Also dilute the standards accordingly. 

Table 2.--Instrwnental parameters for the determination 

of Na, K, Ca, Mg, and cation exchange capacity (C.E.C.) 

[For all determination, rotate the burner 30° from parallel) 

Sample flow Buffer flow 

Wavelength Slit Buffer rate 

Element (nm) (nm) (percent) (mL/min) 

Na---------- 589.6 1.4 0.1 K 1.0 

K----------- 766.7 1.4 .1 Na 1.0 

Ca----------- 422.7 1.4 1.0 La 1. 0 

Mg----------- 285.2 • 7 1.0 La 1.0 

Total C. E. C. 589.6 1. 4 .1 K .6 

rate 

(mL/min) 

6.4 

6.4 

6.4 

6.4 

10.9 
Table 3.--Preparation of standard solutions for cation 

exchange capacity measurements and for measurements of 

exchangeable Ca, K, Mg, and Na 

[After mixing, dilute each standard to 500 m1 using the 

ammonium acetate solution. Store in 16-oz plastic bottles] 

Standard solutions 

Parameter Sl S2 S3 

Amount of 100 meq/L Na 

stock solution (in m1) 3.00 5.00 10.0 

Concentration of Na 

in meq/1-------------- .6 1.0 2.0 

Amount of 100 meq/L K 

stock solution (in m1) 3.0 5.00 10.0 

Concentration of K 

in meq/L-------------- .6 1.0 2.0 

Amount of 100 meq/1 Ca 

stock solution (in m1) 25.0 75.0 125.0 

Concentration of Ca 

in meq/1-------------- 5.0 15.0 25.0 

Amount of 100 meq/1 Mg 

stock solution (in m1) 5.0 10.0 15.0 

Concentration of Mg 

in meq/1-------------- 1.0 2.0 3.0 

Drops of sodium 

hexametaphosphate 

solution-------------- 20 20 20 

4} 

5} 

6} 

The elements Na and K could also be easily 

measured, using the A.A. spectrophotometer 

in the emission mode or a flame photometer. 

Let the solution settle overnight to 

eliminate the fine material that might pass 

through the filter paper. 

The total C.E.C. measurement may be 

smaller or large than the sum of 

Ca+K+Mg+Na, depending on the type of 

soil. For example, in an alkaline soil, free 

halite, gypsum, calcite, or other salts may 

cause a higher cation sum than the 

determined total C.E.C. In some cases 

where these constituents are very small, 

subtracting the water-soluble constituents 

measured in the water-saturation extract 

from the exchangeable cations measured 

will result in better estimates of 

exchangeable amounts. However, when the 

amounts of these constituents are large, the 

data for Ca and Mg should be disregarded 

because some of these minerals are less 

soluble in a water extract than in an acetate 

extract. An estimate of Ca+Mg can be 

obtained by subtracting exchangeable K+Na 

from the C.E.C. value. Correcting 

exchangeable cations for water-soluble 

cations can be done by using the following 

formula: 

XC =XC c u 

(XS} (SI} 

1000 

where XC~ is the corrected exchangeable 

cation value (meq/100 g), XCu is the 

uncorrected exchangeable cation value 

(meq/100 g), XS is the amount of the cation 

measured in the saturation extract (meq/L}, 

5 

and SI is the saturation index (percent). If 

the sample contains appreciable cations not 

analyzed, such as Al, Ba, Fe, H, Li, Mn, or 

Sr, the total C.E.C. can be larger than the 

cation sum, especially if the pH of the soil is 

less than 7. 

7} The soil plug is easily broken up by gently 

rapping the culture tube on a foam pad. Do 

not use a glass rod to break it up. 

8) Extracts should be refrigerated to avoid 

bacterial growth which might alter the 

concentrations. 

Water-Saturation Extract 

A saturation paste of a soil is made to estimate 

the amount of water-soluble salts that a plant would 

be exposed to under field conditions. This extract has 

been described by Bower and Wilcox (1965} and is the 

method presented here. 

Solutions: 

A) 0.01 N potassium chloride: Weigh 0. 7456 g 

of potassium chloride into a 1.0Q-L 

volumetric flask. Dissolve with 

demineralized water and dilute to volume. 

This solution at 25, C has an electrical 

conductivity of 1.412 mmhos/cm. 

B) Concentrated standards, buffers, and sodium 

hexametaphosphate solution used also in the 

C.E.C. determination. 

Procedure: 

1) Weigh and record weight of an 80Q-mL 

beaker and plastic spatula. 

2} Weigh 200.Q-500.0 g of sample into the 

beaker. The sample weight depends on the 

clay content of the sample. Usually, the 

larger the amount of clay, the more sample 

is needed. Record the weight of soil taken. 

3} Mixing with the spatula, add demineralized 

water until a saturated paste is reached. 

The saturation criteria are when the paste 

glistens, flows freely off of the spatula 

(Note 3}, and has no free water standing. 

4} Cover the beaker and let stand for 1 hour. 

Recheck for the saturation criteria. (See 

Note 4.} Add more water if too dry or a 

known weight of soil if water is standing on 

the surface. Mix after each addition. 

5} Re-cover and wait for 3 hours. Check again 

for the saturation criteria. Reweigh to 

obtain the total weight of the soil and water 

mixture. 

6} Transfer paste to a Buchner funnel 

containing a Whatman 41 filter paper. 

Filter under low vacuum, about 20 to 30 

torr, until the paste cracks and draws air 

(See Notes 6-10}. 

Analysis: 

1} 

2} 

3} 

Calibrate the Beckman Solu-Bridge 

Conductivity Bridge, Model SD-26 with the 

0.01 N potassium chloride, thereby 

compensating for room temperature. 

Measure the conductivity of the extract. 

Centrifuge for 5-6 minutes at 2000 rpm. 
4) 

5) 

6) 

Notes: 

1) 

2) 

3) 

4) 

5) 

Filter through a Whatman 41 filter paper 

into a 2-oz plastic bottle. Add two drops of 

concentrated nitric acid and one drop of the 

sodium hexametaphosphate solution per 25 

mL of extract. 

Using demineralized water and a Lab 

Industries Repipet, make 10.0 mL of a 1:50 

dilution of the extract and place it directly 

into the sample tubes of the Perkin-Elmer 

A5-50 auto sampler's carousel. Determine 

Na, K, Ca, and Mg using a Perkin-Elmer 

5000 A.A. spectrophotometer and the 

conditions given in table 4. Also see table 4 

for preparing the standards for determining 

Ca, Mg, Na, and K in solution. Report the 

values as meq/L. A multiplication factor of 

50 is linked to the dilution. 

Chloride and sulfate are determined 

simultaneously using standard Technicon 

Auto Analyzer II equipment. (See Note 

12.) Chloride is determined using an ionselective electrode and Technicon's 

Industrial Method No. 441-76 WE. After a 

1:10 sample-dilution loop, sulfate is 

determined calorimetrically using 

Technicon's Industrial Method No. 118-71 

W/B. 

For this study, plastic disposable 800-mL 

beakers and plastic spatulas were used. The 

plastic beakers were found to be more 

advantageous than glass because the paste 

will flow more freely from them. They also 

proved to be cheaper than glass, because 

they can be washed and reused and will not 

break as readily. 

For convenience, use one spatula per beaker 

and do not remove while weighing. 

Many clay-rich soils will not flow freely off 

the spatula, and sometimes they tend to 

swell two to three times in volume. 

The endpoint for the saturation paste is 

most easily recognized when water is just 

starting to stand on the surface. A very 

small amount of water can be detected. Tip 

the beaker on its side to help notice standing 

water. 

Care must be exercised when preparing 

sandy soils. Substantially smaller amounts 

of water are needed to reach saturation. 

Table 4. --Preparation of standard solutions and pump arrangements 

for determining cations in a water saturation extract 

[For Sl, S2, and S3, use four drops of sodium hexametaphosphate per 

100 mL. See table 2 for the analytical wavelength slit for each element] 

Standard solutions 

Element Sl S2 S3 Buffer Sample Buffer (meq/L) (meq/L) (meq/L) flow rate flow rate 

(mL/min) (mL/min) 

Ca 0.10 0.30 0.60 1.0 pet La 3.2 3.2 Mg .10 .30 .60 1.0 pet La 1.0 6.4 Na .04 .06 .10 0.1 pet K 3.2 3.2 K • 04 .06 .10 .1 pet Na 3.2 3.2 

6 

6) When filtering the paste, an easy-to-clean, 

two-piece, plastic, 9.0-cm Buchner funnel 

was used. This size funnel holds about 150 

mL total volume and is large enough to hold 

the paste from 300 g of most soils. 

7) Filtering was done directly into a 50-mL 

plastic centrifuge tube supported in a 50QmL vacuum flask by a styrofoam pad. 

8) Care must be taken not to have too low of a 

vacuum or the extracts will boil, causing a 

concentration of the extract. 

9) When applying vacuum to very clay-rich 

soils, a layer of impermeable clay will form, 

preventing the complete cracking of the 

paste. In this case, the paste was filtered 

for a maximum of 1 hour, or until no 

additional filtrate was noticed for about 15 

minutes. 

10) A plastic, 40-mesh screen was placed 

between the funnel and the filter paper to 

assist in the filtering. This prevents the 

filter paper from being pulled into and 

therefore clogging the holes of the funnel. 

11) A 1:50 dilution of the extract could also be 

done using a volumetric flask. Using an 

auto-diluter can save a large amount of 

time. 

12) When determining the chloride, the low 

standard was 5 or 10 meq/L chloride, and 

the full-scale, high standard was 50 meq/L. 

Combined chloride and sulfate standards of 

10, 25, and 50 meq/L provide a good working 

range. 

13) Do not let the solutions stand in the plastic 

sample tubes used in the Perkin-Elmer As50 carousel for any length of time. 

Adsorption of the metals onto their surfaces 

may be a problem. 

14) The sample weight was routinely 250 g. 

About 15-25 mL of extract was recovered, 

depending on the clay content of the soil. 

15) The extraction procedure should be followed 

closely, because extracting time, vacuum 

applied, and particle size will affect the salt 

content of the extract (Jacober and 

Sandoval, 1971). 

Hot-Water-Soluble Boron 

Boron is an essential element, but can commonly 

occur at either deficient or toxic levels in soils. The 

method used is modified from that given by Wear 

(1965). The sample is refluxed in a plastic bottle in a 

boiling water bath instead of in a condenser. This 

helps eliminate contamination due to the boron found 

in glassware. 

Procedure: 

1. Weigh 20.0 g of air-dried soil into a 4-oz 

polyethylene bottle. 

2. Add 20.0 mL of distilled water and 0.5 mL 

of 10 percent barium chloride aqueous 

solution • 

3. Manually shake to mix. 
4. 

5. 

6. 

7. 

Note: 

1) 

Immerse into a boiling water bath for 30 

minutes. The boiling water should keep the 

solution mixed. 

Remove and cool to room temperature with 

the bottle upright. 

Decant and filter through a Whatman 41 

filter paper in a polyethylene funnel into a 

2-oz polyethylene bottle. Acidify with two 

to three drops of concentrated nitric acid. 

Determine boron with a d.c. argon plasma at 

249.7 nm with internal background 

correction. See Ball and others (1978) for 

more details of the instrumental setup. 

Care must be taken not to contaminate the 

sample with boron coming from contact with 

regular laboratory glassware. A very high 

(commonly over 2 ppm) boron blank can be 

encountered if this procedure is performed 

in pyrex glass. 

Soil pH 

Measuring the pH, or the negative logarithm of 

the hydrogen ion activity, is one of the most important 

tests performed on a soil. The pH is not only a 

characteristic of the soil, but also a cause and control 

of many reactions in the soil (McLean, 1973). The soil 

is mixed with an equal weight of water and the quasiequilibrium pH determined using a combination pH 

electrode. This 1:1 extract has been described by 

Peech (1965). 

Procedure: 

1. Weigh 20.0 g air-dried soil into 50-mL 

beaker. 

2. Add 20.0 mL water. 

3. Mix well using a glass stirring rod. Repeat 

the stirring every 10 minutes for the next 30 

minutes. Let stand covered for 1 hour. 

4. Immerse a combination glass electrode into 

the solution standing above the soil and 

measure the pH. A 3-minute waiting time 

was used for the electrode to approach 

equilibrium. The pH meter was standardized 

using a pH 7.0 buffer. 

Notes: 

1) 

2) 

3) 

Some of the very clay-rich samples may 

need an additional 20 mL of water in order 

to obtain a water layer deep enough to read 

the pH. Owing to dilution, this should 

normally increase the measured pH. 

The 1-hour waiting time is not critical. A 

longer time may be used. Usually a batch of 

20 samples was run at a given time. 

Therefore, the last sample sat for about 2.5 

hours. At the end, the first samples were 

reread with no significant difference 

between the pH readings. 

Fqr this study disposable plastic beakers and 

sbrrmg rods were used to eliminate 

dishwashing. Fifty-mL glass beakers could 

also be used. 

7 

ERROR DUE TO SAMPLE SPI..ITTING 

For each reference sample, 14 of the 128 splits 

were selected for chemical analysis using the methods 

described above. In addition, 4 of the 14 samples were 

further divided in half to provide an estimate of 

analytical error. The 72 samples (4 reference 

materials times 14 samples plus 4 splits) were placed 

in random order and analyzed in this sequence to 

effectively convert any systematic bias to a random 

error. The nested analysis-of-variance design used to 

estimate variance components between and within 

splits and to estimate analytical error is shown in table 

5. The data resulting from the analysis of variance are 

shown in tables 6-9. 

Because only a few samples of each reference 

material were analyzed, the form of the frequency 

distribution could not accurately be determined (for 

example, see figs. 1 and 2). Elements occurring in 

trace quantities in natural materials commonly exhibit 

positively skewed frequency distributions. Therefore, 

data for all parameters (except pH, which is reported 

as a logarithm) were transformed to their common 

logarithm prior to statistical analysis. Logtransformed data should more closely resemble a 

frequency distribution with a Guassian form than 

should nontransformed data, and the geometric mean 

should be a better measure of central tendency than 

the arithmetic mean. As more splits of each reference 

sample are analyzed, it will become possible to test 

the validity of this transformation for each parameter 

measured on each reference material. 

The variance components for splitting estimate 

errors in the physical process of mixing the samples, 

splitting the samples, and putting them into their 

individual containers. The variance component labeled 

analytical estimates all remaining errors, which are 

due to subsampling, preparing the sample by whatever 

method is necessary to obtain an appropriate solution 

for chemical analysis, the actual analysis, any 

calculations, and transcribing the data and 

transmitting it to the person requesting the analysis. 

8 11

~68 percent~.& 20. 9.0 5 

7.3 1-------95.4 percent------! 25.

3 f-----------99.7 percent•------------l 

14 

GM 

frequency 

TOTAL Cu IN SAMPLE A, IN PARTS PER MILLION 

Figure 1.-~ actual ('J?ars) and theoretical (line) 

frequency distribution for total copper in Sample 

A. Geometric mean (GM), 13.7. ~ expected range 

of total copper at the probability level indicated. 

26 
13.0 13j!_95.4 percent~.4 18.5 

1----99.7 percent---! 

16 

GM 

DTPA-EXTRACT ABLE Fe IN SAMPLE A, 

IN PARTS PER MILLION 

8 

Figure Z.-~ actual {bars) and theoretical {line) 

frequency distreibution for DTP A-extractable 

iron in sample A. Geometric mean {GM), 15.5. ~ 

expected range of DTP A-extractable iron at the 

probability level indicated. 

The statistical design used here only gives an estimate 

of each error component, splitting and analytical. In 

order to insure that an analytical error was not 

interpreted as a splitting error, each individual sample 

would need to be analyzed in the laboratory at least 

twice. 

In tables 6-9, the data for total element content 

provide the best information on how well the samples 

were homogenized, because a determination of total 

element content is not subject to the many laboratory 

variables that may affect a determination of 

extractable element content. Many extractions are 

nonequilibrium reactions and may be affected by such 

factors as sample preparation, extraction technique, 

extraction time, and the element being determined. If 

homogeneity of samples is indicated by the data for 

total element content, then this homogeneity can be 

assumed when interpreting the extractable element 

data. 

Interpretation of the variance components in 

tables 6-9 can be made relative to the following 

hypothetical statements: If the sample-splitting 

process contained no significant error, then the total 

variance should reflect only analytical imprecision. If 

the various steps in chemical analysis contained no 

significant error, then the analytical error variance 

would be zero and any error would be distributed 

among the levels of the statistical design reflecting 

only splitting errors. If those splitting errors were 

constant, then error variance at each level of the 

statistical design would be equally distributed. 

Total content of any element at any single level 

of the statistical design shows no consistent significant 

variance component {tables 6-9). Significance is 

determined by the conventional F-ratio at the 0.05 

probability level. The random distribution of 

significant variance components among levels of the 

statistical design indicates that both splitting and 

analytical errors are probably not systematic, but tend 

to be random. Therefore, adequate homogenization of 

all four reference samples can be assumed. 

Table 5.--unbalanced, nested, analysis-of-variance design used to estimate splitting and analytical error 

Source of 

variation 

a--8-gallon splits--

b--4-gallon splits--

c--2-gallon splits--

d--1-gallon splits--

e--1/2-gallon splits 

f--1/4-gallon splits 

g--1/8-gallon splits 

h--Analytical-------

Degrees of 

freedom 

1Leaders (---), no F-ratio exists. 

Mean-square estimates F-ratio1 Variance component 

2 MS 1 - MS2 2 s = 8.9 .. 0 a a 

2 Ms2·- MSJ 2 s = b 1.8 .. ~ 

2 MS3 - MS4 2 s = 1. 7 .. 0 c c 

2 MS4 - MS5 2 s - d 1.7 " od 

s 

2 = 

MS5 - MS6 2 

2.2 .. 0 e e 

2 2 2 2 MS5 • sh + 1.5 sg + 1. 7 sf + 2.2 se MS5/Ms6 

2 MS6 - MS7 2 s - 2.0 ,. of f 

2 2 2 MS6 = sh + 1.5 sg + 2.0 sf MS6/MS 7 

2 MS7 - MS8 2 s - 1.3 .. 0 g g 

2 2 

sh ,. oh 

8 
Table 6.--Variance components attributed to splitting and analyses of Sample A 

[*, variance component significantly different from zero at the 0.05 probability level; level, source of 

variation as indicated in table 5) 

Total 

Parameter log10 

Ca-------

Co-------

Cu-------

Fe-------

K--------

Mg-------

Mn-------

Na-------

Zn-------

variance 

0.00185 

.00641 

.01046 

.00045 

.00010 

.00011 

.00041 

.00009 

.00035 

Cu------- 0.00200 

Fe------- .00068 

Mn------- .00097 

Pb------- .01733 

Zn------- .00184 

C.E.c. 1--

Ca-------

K--------

Na-------

Mg-------

s.c. 2----

ea-------

,Cl------- .K--------

Na-------

Mg-------

so4------

0.00024 

.00209 

.04296 

.00045 

.00020 

0.00086 

.00182 

0 

.03414 

.00209 

.00509 

.00308 

Level h, Level g, 

8-gallon 4-gallon 

splits splits 

4.6 

10.0 

0 

0 

16.1 

0 

0 

15.8 

0 

8.1 

22.5 

11.2 

5.9 

8.7 

11.2 

9.1 

5.3 

0 

0 

7.1 

0 

0 

9.4 

*16.0 

19.5 

18.0 

6.9 

0 

0 

8.0 

0 

31.9 

18.5 

0 

*29.1 

0 

0 

0 

.9 

0 

0 

0 

0 

24.8 

33.8 

12.5 

24.3 

0 

0 

10.1 

0 

0 

Percentage of total variance 

Level f, 

2-gallon 

splits 

Level e, 

!-gallon 

splits 

Level d, Level c, Level b, 

1/2-gallon 1/4-gallon 1/8-gallon 

splits splits splits 

Based on total content 

0 

0 

0 

5.4 

0 

0 

0 

33.5 

0 

26.6 

0 

*70.3 

11.0 

19.6 

15.5 

0 

3.6 

13.0 

0 

0 

0 

0 

19.6 

0 

0 

16.2 

0 

Based on DTPA extract 

0 

8.8 

0 

0 

0 

37.8 

0 

53.6 

14.3 

*91.3 

12.1 

29.8 

0 

1.4 

0 

Based on exchangeable cations 

0 

1.6 

8.8 

0 

*46. 7 

25.1 

14.2 

.5 

42.4 

0 

0 

0 

0 

0 

0 

Based on saturation extract 

0 

0 

0 

*45.5 

0 

0 

0 

12.3 

*8.1 

0 

0 

17.7 

20.3 

11.9 

0 

0 

0 

0 

0 

0 

0 

0 

0 

7.8 

0 

0 

0 

0 

0 

10.4 

0 

*22.1 

4.0 

0 

0 

0 

*40.9 

0 

*22.1 

0 

0.6 

22.8 

0 

20.7 

15.7 

20.4 

20.7 

28.8 

0 

0 

56.4 

0 

18.7 

46.4 

0 

2.9 

0 

10.7 

31.2 

0 

0 

0 

0 

*82.6 

5.6 

0 

24.0 

0 

0 

0 

0 

0 

21.3 

Measured by specific-ion electrode 

pH3______ 0.08953 0 

s.r.4 ____ o.00146 *18.2 

1cation exchange capacity. 

;specific conductance at 25°C. 

4

variance is arithmetic. 

Saturation index. 

27.2 

11.2 

19.0 0 3.2 0 38.1 

Based on water-saturation extract 

0 4.0 0 13.4 0 

9 

Level a, 

analytical 

error 

33.1 

90.0 

21.9 

19.3 

44.7 

33.9 

35.1 

30.9 

44.6 

42.0 

6.1 

0 

77.5 

0 

63.7 

34.2 

2.8 

5.1 

19.5 

43.5 

44.8 

0 

24.4 

40.5 

39.8 

28.1 

l2.5 

53.2 
Table 7.--Variance comEonents attributed to SElitting and anal~ses of SamEle B 

[*, variance component significantly different from zero at the 0.05 probability level; level, source of 

variation as indicated in table 5] 

Total Percentage of total variance 

Parameter loglO 

Level h, Level g, Level f, Level e, Level d, Level c, Level b, Level a, 

variance 8-gallon 4-gallon 2-gallon !-gallon 1/2-gallon 1/4-gallon 1/8-gallon analytical 

splits splits splits splits splits splits splits error 

Based on total content 

Ca------- 0.00031 7.7 0 0 0 0 33.1 0 59.2 

Co------- .03044 0 *62.8 2.2 0 0 1.2 1.4 32.4 

Cu------- .00082 0 9.8 0 25.5 6.5 13.3 0 44.9 

Fe------- .00026 4.2 .8 0 13.1 35.7 0 0 46.2 

K-------- .00010 5.4 0 0 25.9 28.5 0 0 40.2 

Mg------- .00018 0 6.7 0 7.0 0 26.1 0 60.2 

Mn------- .00025 0 0 16.7 ·o 3.0 0 *72. 8 7.5 

Na------- .00016 80 0 0 0 26.8 17.5 0 47.7 

Zn------- .00028 0 *74.9 0 0 *14.9 4.3 0 5.9 

Based on DTPA extract 

Cd------- 0.00996 0.8 0 *71. 8 0 0 0 0 27.4 

Cu------- .00095 0 *60.6 0 0 0 4.0 2.9 32.5 

Fe------- .00600 0 24.4 8.1 0 .4 0 0 67.1 

Mn------- .00263 0 7.6 8.7 0 1.7 8.2 0 73.8 

Pb------- .03014 16.5 0 3.3 0 17.4 0.2 0 62.6 

Zn------- .00122 0 *82.5 4.6 0 3.6 .9 0 8.4 

Based on exchangeable cations 

C.E.c. 1-- 0.10253 0 *38.9 *6.0 0 0 0 *52.3 2.8 

Ca------- .02903 1.7 *16.0 0 10.2 0 29.4 0 42.7 

K-------- .01343 0 27.5 0 0 0 0 23.5 49.0 

Na------- .00040 20.8 2.5 0 0 0 0 58.0 18.7 

Mg------- .00155 12.0 4.3 0 22.6 0 19.8 .1 41.2 

Based on saturation extract 

s.c. 2---- 0.00491 0 0 17.3 0 15.2 17.2 0 50.3 

Ca------- .40922 25.2 0 0 *44. 9 3.7 14.8 0 11.4 

Cl------- 0 0 0 0 0 0 0 0 0 

K-------- .11574 7.5 *11.8 0 34.7 0 *35.3 3.2 7.5 

Na------- .01020 0 0 10.6 0 23.3 *13.1 0 53.0 

Mg------- .21665 25.0 0 0 *46. 6 5.5 1.5 10.8 10.6 

804------ .00603 .9 0 *68.3 0 7.2 3.1 0 20.5 

Measured by specific-ion electrode 

pH3 ______ 0.04194 0 *45.1 6.8 0 0 0 *45.1 3.0 

Based on water-saturation extract 

s.r.4 ____ 0.00272 0 39.1 *29.8 0 0 *12.1 0 19.0 

~Cation exchange capacity. 

c. 3

specific conductance at 25° 

4

variance is arithmetic. 

Saturation index. 

10 
Table B.--Variance components attributed to splitting and analyses of Sample C 

[*, variance component significantly different from zero at the 0.05 probability level; level, source of 

variation as indicated in table 5] 

Total 

Parameter 

variance 

Ca------- 0.00079 

Co------- .02438 

Cu------- .00589 

Fe------- .00193 

K-------- .00021 

Mg------- .00162 

Mn------- .00073 

Na------- .00009 

Zn------- .01434 

Cd-------

Cu-------

Fe-------

Mn-------

Pb-------

Zn-------

c.E.c. 1--

ca-------

K--------

Na-------

Mg-------

s.c. 2----

ca-------

Cl-------

K--------

Na-------

Mg-------

0.02399 

.00326 

.00097 

.00211 

.07567 

.00237 

0.02195 

.00044 

.03212 

.02500 

.00120 

0.00380 

.00151 

0 

.00852 

.00555 

.00146 

Level h, Level g, 

8-gallon 4-gallon 

splits splits 

0 

3.2 

0 

0 

3.2 

2.8 

1.1 

.2 

12.3 

*38.0 

9.3 

.8 

0 

0 

.5 

11.8 

28.6 

11.0 

13.4 

1~.3 

17.3 

11.5 

0 

0 

0 

9.6 

*63.3 

0 

*58.7 

0 

0 

0 

0 

10.4 

0 

0 

0 

7.0 

*47 .6 

20.7 

0 

0 

0 

0 

0 

0 

0 

6.0 

0 

*67.5 

0 

12.7 

Percentage of total variance 

Level f, 

2-gallon 

spliU 

Level e, 

!-gallon 

splits 

Level d, Level c, Level b, 

1/2-gallon 1/4-gallon 1/8-gallon 

splits splits splits 

Based on total content 

0 

36.3 

2.5 

21.5 

10.5 

*18.0 

*51.1 

0 

0 

0 

0 

0 

0.5 

0 

0 

0 

41.3 

0 

16.9 

*15.1 

10.2 

4.6 

21.8 

23.5 

19.6 

4.5 

0 

Based on DTPA extract 

0 

0 

3.1 

0 

0 

7.4 

0 

0 

0 

0 

24.0 

0 

7.3 

58.7 

*47 .8 

18.4 

3.0 

28.9 

Based on exchangeable cations 

1.7 

0 

*52. 7 

*75. 7 

*47.4 

0 

0 

0 

.9 

0 

0 

39.6 

5.7 

0 

1.7 

Based on saturation extract 

3.2 

0 

0 

0 

15.7 

0 

0 

8.6 

0 

*19.1 

6.9 

11.8 

35.9 

0 

0 

.3 

0 

0 

0 

0 

4.4 

0 

0 

0 

0 

0 

0 

0 

0 

10.2 

1.0 

0 

0 

0 

31.8 

0 

.7 

0 

3.8 

*19.8 

0 

.4 

38.6 

1.0 

0 

32.6 

0 

43.3 

26.8 

*47.1 

7.1 

0 

0 

*48. 2 

32.0 

0 

14.1 

0 

15.8 

0 

0 

11.4 

0 

19.9 

0 

0 

0 

0 

0 

0 

Measured by specific-ion electrode 

pH3______ 0.05785 13.4 

s.r. 4---- o.ooos8 *35.3 

1cation exchange capacity. 

;specific conductance at 25°C. 

Variance is arithmetic. 

4saturation index. 

0 

5.2 

43.1 3.9 0 1.5 27.4 

Based on water-saturation extract 

0 12.7 0 0 15.3 

11 

Level a, 

analytical 

error 

19.8 

12.8 

24.2 

30.1 

37.7 

8.6 

21.1 

43.6 

87.7 

6.5 

0 

31.1 

18.9 

52.3 

47.4 

86.5 

0 

19.2 

9.3 

14.7 

39.8 

54.1 

0 

12.7 

38.8 

64.9 

10.7 

31.5 
Table 9.--Variance com2onents attributed to s2litting and analises of Samele D 

[*, variance component significantly different from zero at the 0.05 probability level; level, source of 

variation as indicated in table 5] 

Total Percentage of total variance 

Parameter loglO 

Level h, Level g, Level f, Level e, Level d, Level c, Level b, Level a, 

variance 8-gallon 4-gallon 2-gallon !-gallon 1/2-gallon 1/4-gallon 1/8-gallon analytical 

splits splits splits splits splits splits splits error 

Based on total content 

Ca------- 0.00089 12.0 0 54.5 0 *22.9 2.3 0 8.3 

Co------- .01210 0 36.9 11.6 0 0 0 0 51.5 

Cu------- .00754 9.7 0 *23. 7 0 23.6 0 0 43.0 

Fe------- .00039 0 1.6 0 15.4 7.2 18.0 0 57.8 

K-------- .00008 10.4 0 43.9 0 0 0 14.8 30.9 

Mg------- .00103 6.6 16.4 0 9.0 0 *18.2 0 49.8 

Mn------- .00070 7.7 0 0 17.5 *28.0 0 20.9 25.9 

Na------- .. 00039 5.2 1.5 0 0 0 26.8 0 66.5 

Zn------- .00026 0 45.7 0 12.6 0 5.1 9.7 26.9 

Based on DPTA extract 

Cd------- 0.01588 9.2 0 0 90.8 0 0 0 0 

Cu------- 0 0 0 0 0 0 0 0 0 

Fe------- • 00119 0 18.0 0 0 .6 0 0 81.4 

Mn------- .00440 0 23.0 0 0 0 .6 0 76.4 

Pb------- .0192 0 18.3 0 5.2 0 20.4 0 56.1 

Zn------- .00654 17.5 6.0 0 22.2 0 0 54.3 0 

Based on exchangeable cations 

C.E.c. 1-- 0.00086 3.1 0 5.8 0 12.0 6.0 0 73.1 

Ca------- .00074 15.8 0 0 33.3 0 0 2.7 48.2 

K-------- .02666 0 24.8 6.9 0 0 *29.3 0 39.0 

Na------- .00454 8.9 0 0 2.3 0 17.3 0 71.5 

Mg------- .00044 1.3 7.5 0 36.4 10.2 *5.3 0 39.3 

Based on saturation extract 

s.c. 2---- 0.00043 17.4 0 *46.1 0 0 0 4.3 32.2 

Ca------- .00080 0 0 36.1 0 0 0 19.4 44.5 

Cl------- 0 0 0 0 0 0 0 0 0 

K-------- .01270 11.5 0 0 0 2.8 11.1 0 74.6 

Na------- .00436 17.7 0 0 5.6 5.7 .5 0 70.5 

Mg------- .00159 0 15.7 0 0 0 0 30.0 54.3 

Measured by specific-ion electrode 

pH3 ______ 0.12433 7.2 0 0 15.4 0 18.1 0 59.3 

Based on water-saturation extract 

s.r. 4---- 0.00063 11.1 0 8.6 0 0 0 17.2 63.1 

1cation exchange capacity. 

;specific conductance at 25°C. 

Variance is arithmetic. 4saturation index. 

12 
ERROR DUE TO LABORATORY ANALYSIS 

Tables 10-13 give statistics that summarize the 

total and extractable element composition of each of 

the four reference samples. For total content of most 

elements and for all four samples, the observed ranges 

in tables 10-13 are generally within the accepted 

relative standard deviation for flame A.A.S. of 5 

Table 10.--Statistical siBJimary for repeated analyses of Sample A 

[Ratio, number of samples in which the parameter was found in measurable 

concentrations relative to the niBJiber of samples analyzed; means and 

deviations are geometric, except as indicated; <, less than; leaders 

(--), no data available) 

Parameter1 

Ca, pet------

Co, ppm------

Cu, ppm------

Fe, pet-----

K, pet----

Mg, pet-----

Mn, ppm-----

Na, pet-----

Zn, ppm-----

Cd, ppm-----

Cu, ppm-----

Fe, ppm-----

Mn, ppm------

Pb, ppm------

Zn, ppm------

c.E.c. 2 , meq/100 g 

Ca~, meq/ 100 g----

Ca , meq/100 g----

K3, meq/ 100 g-----

K4 meq/ 100 g-----

Na ~, meq/100 g----

Na4 , meq/100 g---

=:!: :::~~~~ :=== 

s.c.5, mmhos/cm--

Ca, meq/L---------

K, meq/L----------

Na, meq/L--------

Mg, meq/L---------

S04, meq/L--------

Cl, meq/L---------

B, ppm----------

Ratio Geometric Geometric Geometric 

mean deviation error 

Based on total content 

18:18 0.31 1.104 1.059 

18:18 6.6 1.202 1.191 

18:18 13.7 1.266 1.117 

18:18 1.94 1.050 1.022 

18:18 1.91 1.023 1.016 

18:18 .40 1.024 1.014 

18:18 202 1.048 1.028 

18:18 1.49 1.022 1.012 

18:18 42 1.044 1.029 

Based on DTPA extract 

2:18 

18:18 .73 1.109 1.069 

18:18 15.5 1.062 1.015 

18:18 1.2 1.074 1.000 

18:18 1.1 1.354 1.306 

18:18 .72 1.104 1.000 

Based on exchangeable cations 

18:18 22.0 1.037 1.029 

18:18 7.6 1.111 1.064 

18:18 6.4 1.141 1.073 

18:18 .40 1.612 1.083 

18:18 .35 1.676 1.102 

18:18 32.5 1.050 1.011 

18:18 13.9 1.223 1.021 

18:18 2.5 1.033 1.015 

18:18 1.8 1.074 1.037 

Based on water-saturation extract 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

40.1 

23.8 

.86 

375 

14.2 

348 

.5 

1.070 

1.103 

1.530 

1.111 

1.178 

1.136 

1.000 

1.045 

1.068 

1.234 

1.069 

1.109 

1.070 

1.000 

Based on hot-water extract 

0:18 (0.5 

Measured by specific-ion electrode 

pH6-------------- 18:18 7 .s 0.292 0.106 

Based on calculated parameter 

S.I.7, pet------- 18:18 49.4 1.092 1.066 

Observed range 

0.30 

5.0 

12 

1.85 

1.86 

.39 

190 

1.45 

41 

(0.05 

.7 

14.6 

1.1 

.8 

.7 

21.3 

6.8 

s. 7 

.29 

.25 

31 

11 

2.4 

1.6 

38.2 

21.8 

.7 

350 

12.5 

310 

.5 

- 0.35 

8.0 

20 

2.02 

1.94 

.41 

-210 

- 1.53 

- 45 

- 0.05 

.8 

16.7 

1.3 

1.6 

.8 

- 23.1 

8.6 

7.5 

- .61 

- .57 

- 34 

- 16 

2.6 

1.9 

- 43.7 

- 27.4 

1.4 

-430 

- 17.4 

-410 

.5 

(0.5 - <O.S 

7.2 7.9 

44.9 - 57.2 

1pct, percent; ppm, parts per million; meq/100 g, mi11iequivalents per 100 

grams; mmhos/cm, reciprocal milliohms per centimeter at 25 degrees 

2

Celsius; meq/L, milliequivalents per liter. 

3~:~~~: ~~~:~~:~t~:P~~!t~he fraction soluble in water. 

~Values corrected for amounts measured in the water-saturation extract. 

Specific conductance. 

~:::;a!~:!a~~:~. and error are arithmetic. 

13 

percent. This narrow observed range would also 

indicate that adequate homogenization of each sample 

was achieved and that any splitting errors are within 

acceptable limits. Therefore, the reasons for less 

precision in the determination of extactable elements 

must be related to the character of the samples and to 

the factors in the laboratory procedure that may 

influence the amount of the element extracted. 

Table H.--Statistical summary for repeated analyses of Sample B 

[Ratio, niDDber of samples in which the parameter was found in measurable 

concentrations relative to the number of samples analyzed; means and 

deviations are geometric, except as indicated; <, less than; leaders (--) 

no data available) 

Parameter1 

Ca, pet---------

Co, ppm---------

Cu, ppm--------

Fe, pet-------

K, pet---------

Mg, pet--------

Mn, ppm--------

Na, pc t---------

Zn, ppm--------

Cd, ppm--------

Cu, ppm--------

Fe, ppm--------

Mn, ppm---------

Pb, ppm--------

Zn, ppm---------

c.E.c. 2 , meq/100 g 

ca3, meq/ 100 g----

ca4 , meq/100 g----

K3, meq/100 g-----

K4 meq/100 g-----

Na~. meq/100 g----

Na4 , meq/100 g---

Mg3 , meq/100 g----

Mg4, meq/100 g----

s.c. 5, mmhos/cm--

Ca, meq/L---------

K, meq/L----------

Na, meq/ L---------

Mg, meq/L---------

so4, meq/L--------

Cl, meq/L---------

B, ppm-----------

Ratio Geometric Geometric Geometric 

mean deviation error 

Based on total content 

18:18 2. 76 1.041 1.032 

18:18 9.6 1.494 1.257 

18:18 24.8 1.068 1.045 

18:18 2.02 1.038 1.026 

18:18 1. 72 1.024 1.015 

18:18 1.42 1.031 1.024 

18:18 358 1.037 1.010 

18:18 1.03 1.029 1.020 

18:18 75.7 1.039 1.009 

Based on DTPA extract 

18:18 0.11 1. 258 1.128 

18:18 2.3 1.074 1.041 

18:18 84.0 1.195 1.157 

18:18 4.6 1.125 1.107 

18:18 2.4 1.491 1.372 

18:18 7.8 1.084 1.024 

Based on exchangeable cations 

18:18 23.0 2.090 1.132 

18:18 13.8 1.483 1.292 

18:18 13.1 1.510 1.297 

18:18 .54 1.306 1.205 

18:18 .46 1.449 1.214 

18:18 9. 7 1.047 1.020 

18:18 7 .o 1.107 1.077 

18:18 3.8 1.095 1.060 

18:18 3.3 1.259 1.069 

Based on water-saturation extract 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

0:18 

1.5 

2. 7 

.45 

16.4 

2.4 

7. 7 

(.5 

1.175 

4.362 

2.189 

1.262 

2.920 

1.196 

Based on hot-water extract 

0:18 (0.5 

1.121 

1.644 

1.237 

1.185 

1.418 

1.084 

Measured by specific-ion electrode 

pH6-------------- 18:18 9.0 0.025 0.035 

Based on calculated parameter 

s.1. 7 , pet------- 18:18 164.1 1.128 1.054 

Observed range 

2.57 

5 

23 

1.94 

1.68 

1.32 

350 

1.00 

73 

0.09 

2.1 

72.6 

4.2 

1.1 

7.5 

8.6 

9.2 

8.9 

.41 

.28 

9.0 

6.2 

3.4 

2.2 

1.3 

1.0 

.27 

13.6 

1.2 

6. 5 

<.5 

- 2. 79 

- 12 

- 27 

- 2.09 

- 1. 75 

- 1.45 

-370 

- 1.06 

- 79 

- 0.14 

2.5 

- 99.4 

5.2 

3.1 

- 8.9 

53 

19.5 

19.3 

.74 

.69 

10.2 

7.8 

4.1 

3.9 

1.8 

- 15.5 

1.3 

- 19.6 

9.4 

- 10.0 

(.5 

(0.5 - (0.5 

8.8 9.3 

141.6 - 178.4 

1pct, percent; ppm, parts per million; meq/100 g, milliequivalents per 100 

grams; mmhos/cm, reciprocal milliohms per centimeter at 25 degrees 

2

celsius; meq/L, mi11iequivalents per liter. 

Cation excliange capacity. 3values uncorrected for the fraction soluble in water. 4values corrected for amounts measured in the water-saturation extract. 5specific conductance. 6Mean, deviation, and error are arithmetic. 7 Saturation index. 
The observed range for all elements, except Pb, 

extracted by DTPA from Sample A (table 10) is 

narrow, indicating that acceptable analytical precision 

was achieved. For Sample B, the wider observed range 

in DTPA-extractable elements (table 11) indicates that 

less analytical precision was achieved with this 

sample. Several factors may account for this drop in 

precision. A very fine clay-sized suspension was 

persistent in Sample B, even after centrifuging. The 

Table 12.--Statistical summary for repeated analyses of Sample C 

[Ratio, number of samples in which the parameter was found in measurable 

concentrations relative to the number of samples analyzed; means and 

deviations are geometric, except as indicated; <, less than; l.eaders 

(--), no data available] 

Parameter1 

Ca, pet----------

Co, ppm----------

Cu, ppm----------

Fe, pc t----------

K, pc t-----------

Mg, pet----------

Mn, ppm--------

Na, pet----------

Zn, ppm----------

Cd, ppm---------

Cu, ppm----------

Fe, ppm---------

Mn, ppm----------

Pb, ppm--------

Zn, ppm----------

Ratio 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

18:18 

11:18 

18:18 

18:18 

18:18 

18:18 

18:18 

Geometric Geometric Geometric 

mean deviation error 

Based on total content 

.61 1.067 

3.5 1.433 

10.3 1.193 

.so 1.107 

2.65 1.034 

.16 1.097 

265 1.064 

1.50 1.023 

29.8 1.317 

Based on DTPA extract 

0.051 

.57 . 

22.1 

21.5 

.48 

.65 

1.429 

1.11+1 

1.074 

1.111 

1.884 

1.119 

1.029 

1.137 

1.091 

1.057 

1.021 

1.028 

1.029 

1.015 

1.295 

1.095 

1.000 

1.041 

1.047 

1.581 

1.080 

Based on exchangeable cations 

C.E.c. 2, meq/100 g 18:18 9.5 1.407 1.373 

ca3 , meq/100 g---- 18:18 6.4 1.050 1.000 

ca4 , meq/100 g---- 18:18 6.3 1.050 1.001 

K3 , meq/ 100 g----- 18:18 .43 1.511 1.199 

Observed range 

0.55 - 0.65 

3 5 

8 11 

.71 - .85 

2.57 2. 74 

.15 .17 250 - 285 

1.45 - 27 -

<0.05 -

.5 

20.5 

19.9 

.3 

.6 

8.2 - 6.2 

6.1 

.33 -

1.54 

56 

0.06 

.6 

23.6 

24.7 

1.0 

.7 

21.2 

6.8 

6. 7 

.85 

K4 meq/100 g----- 18:18 

Na1, meq/100 g---- 18:18 

.41 1.524 1.206 .31 - .86 . 

1.07 1.439 1.118 .89 - 2.1 

Na4 , meq/100 g---- 18:18 1.06 1.442 1.119 

Mg3, meq/100 g---- 18:18 1.1 1.083 1.031 

Mg4, meq/100 g---- 18:18 1.1 1.086 1.031 

.88 - 2.1 

1.0 1.2 

1.0 1.2 

Based on water-saturation extract 

s.c.5' mmhos/cm-- 18:18 0.59 1.152 1.094 o.so - 0.66 Ca, meq/L--------- 18: 18 5.0 1.093 1.068 4.5 5.4 

K, meq/L---------- 18:18 .63 1.237 1.079 .56 - .86 Na, meq/L--------- 18:18 .28 1.187 1.113 .23 .35 Mg, meq/L--------- 18:18 1.37 1.092 1.073 1.2 1.5 

so4 , meq/L-------- 0:18 <1.0 (1.0 (1.0 

Cl, meq/L------- 18:18 1.0 1.000 1.000 1.0 1.0 

Based on hot-water extract 

B, ' ppm---------- 0:18 (0.5 <0.5 - <0.5 

Measured by specific-ion electrode 

pH6------------- 18:18 7.2 0.241 0.079 6.9 7.5 

Based on calculated parameter 

s.r.7, pet------ 18:18 23.7 1.057 1.032 22.3 - 25.5 

1pct, percent; ppm, parts per million; meq/100 g, milliequivalents per 

100 grams; mmhos/cm, reciprocal milliohms per centimeter at 25 degrees 

2

Celsius; meq/L, milliequivalents per liter. 

~~:~!~: ~:~~:~:~t~:P~~!t~~e fraction soluble in water. 

5 Values corrected for amounts measured in the water-saturation extract. 

6 

Specific conductance. 

7

Mean, deviation, and error are arithmetic. 

Saturation index. 

14 

pH of this sample was about 9.0, and the DTPA 

extractant was buffered at pH 7 .3. Perhaps significant 

dissolution of iron oxy-hydroxide coatings occurred 

differentially from sample to sample. This could also 

account for the wide observed range in other metals, 

because oxy-hydroxides are good scavengers of trace 

metals (Jenne, 1968). For Sample C (table 1Z), the 

observed range for DTPA-extractable elements 

suggests that adequate analytical precision was 

Table 13.-Statistical sta~~ary for repeated analyses of Sample D 

[Ratio, number of samples in which the parameter was found in measurable 

concentrations relative to the number of samples analyzed; means and 

deviations are geometric, except as indicated; <, less than; leaders 

(--), no data available] 

Parameter1 

Ca, ppm--------

Co, ppm--------

Cu, ppm--------

Fe, pet------.,-

K, pet--------

Mg, pet----------

Mn, ppm--------

Na, pet--------

Zn, ppm--------

Cd, ppm--------

Cu, ppm---------

Fe, ppm----------

Mn, ppm----------

Pb, ppm----------

Zn, ppm----------

Ratio 

18:18 

18:18 

18:18 

18:18 

1,8:18 

18:18 

18:18 

18:18 

18:18 

2:18 

18:18 

18:18 

18:18 

18:18 

18:18 

Geometric Geometric Geometric 

deviation error 

Based on total content 

0.54 1.071 

4.3 1.288 

14.3 1.221 

1.45 1.046 

2.05 1.021 

.33 1.077 

392 1.063 

.92 1.046 

36.3 1.038 

Based on DTPA extract 

.8 

12.9 

19.9 

1.0 

.55 

1.000 

1.083 

1.165 

1.375 

1.205 

1.020 

1.199 

1.140 

1.035 

1.012 

1.053 

1.032 

1.038 

1.019 

1.000 

1.074 

1.143 

1.270 

1.000 

Based on exchangeable cations 

C.E.c.2, meq/100 g 18:18 18.5 1.070 1.060 

ca3, meq/100 g---- 18:18 13.1 1.065 1.044 

ea4 , meq/100 g---- 18:18 12.9 1.065 1.045 

K3, meq/ 100 g---- 18: 18 .so 1.456 1.265 

K4 meq/100 g----- 18:18 .50 1.462 1.268 

Na1, meq/100 g---- 18:18 1.05 1.168 1.140 

Na4 , meq/100 g---- 18:18 1.05 1.169 1.141 

Mg3, meq/ 100 g--- 18:18 2.6 1.050 1.031 

Mg4, meq/100 g---- 18:18 2.6 1.050 1.031 

Based on water-saturation extract 

s.c. 5 , mmhos/cm-- 18:18 o.so 1.049 1.027 

Ca, meq/ L--------- 18: 18 4.3 1.067 1.044 

K, meq/L---------- 18:18 .23 1.296 1.251 

Na, meq/L-------- 18:18 .30 1.164 1.136 

Mg, meq/L-------- 18:18 1.05 1.096 1.070 

so4 , meq/L-------- 0:18 (1.0 

Cl, meq/L--------- 18:18 1.0 1.000 1.000 

Based on hot-water extract 

B, ppm----------- 0:18 <0.5 

Measured by specific-ion electrode 

pH6-------------- 18:18 7.7 0.353 0.272 

Based on calculated parameter 

s.r.7, pet------- 18:18 29.2 1.060 1.047 

Observed range 

0.50 - 0.60 

3 6 

12 - 20 

1.40 - 1.52 

2.00 - 2.10 

.32 - .36 

360 -420 

.88 - .95 

35 - 38 

<0.05 - 0.06 

.8 .8 

12 - 14 

17.2 - 23.4 

• 7 - 1.5 

.5 .7 

17.2 - 20.8 

12.0 - 14.2 

11.9 - 14.1 

.37 - .70 

.36 - .69 

.94 - 1.2 

.93 - 1.2 

2.5 2.8 

2.5 .- 2.8 

0.48 - 0.53 

4.0 4.6 

.19 - .32 

.25 - .37 

.97 - 1.2 

(1.0 1.0 

1.0 1.0 

<0.5 - <0.5 

7.2 8.1 

26.9 - 31.5 

1pct, percent; ppm, parts per million; meq/100 g, milliequivalents per 100 

grams; mmhos/cm, reciprocal milliohms per centimeter at 25 degrees 

2

eelsius; meq/L, milliequivalents per liter. 

Cation exchange capacity. 

~~=~~== ~:~;:~;~~e:o; :m!~:t!r:~=!::e: ~:b!~e i:a::~~;:turation ext tact. 

Sspecific conductance. 

6Mean, deviation, and error are arithmetic. 7 Saturation index. 
achieved and that factors affecting the amount of an 

element extracted were constant. In table 13, the 

observed range in DTPA-extractable metals for 

Sample D also indicates adequate analytical precison, 

except for Mn. In general, for the DTPA extraction, 

when the natural soil pH is much different from that 

of the buffered extracting solution (as in Sample B), 

analytical precision is affected, especially for Fe. In 

all four reference samples, however, the observed 

range was greatest for Pb, probably because the 

amounts determined were near the lower detection 

limit. Much care must be taken to standardize the 

laboratory procedure for this extraction because it is a 

nonequilibrium extraction and will be influenced by 

many aspects of the extraction technique. Also, the 

amounts of the various metals present may affect the 

amounts of any single metal extracted, because DTP A 

is a generalized chelating agent. 

Cation exchange capacity and exchangeablecatio:p determinations for Sample A (table 10) exhibit 

narrow ranges, indicating adequate analytical 

prec1s1on. However, the large difference between 

C.E.C. and the uncorrected sum of the exchangeable 

cations indicates a need to correct for soluble 

cations. Exchangeable Na appears to be much too 

high. This probably reflects a sodium salt of sulfate or 

bicarbonate that was partially dissolved by the 

exchanging solution. When corrected for soluble 

cations, the sum of exchangeable cations is in good 

agreement with C.E.C. The large observed range for 

C.E.C. and for exchangeable cations for Sample B 

indicates that a serious problem exists when using 

these methods on this sample. In Sample B, problems 

in removing a very fine clay-sized suspension existed. 

This could explain the lack of precision. An 

ultracentrifuge would be necessary to remove this fine 

clay from suspension. For Sample C, the observed 

range in C.E.C. is quite large; however, when 

corrected for water-soluble cations the exchangeablecation determinations seem to be reasonably precise. 

The most precise results for C.E.C. and exchangeable 

cations were for Sample D. In general, C.E.C. and 

exchangeable-cation determinations, using the method 

proposed, result in precision that is lower than desired 

for reference samples. The data for these samples 

also show that correcting the exchangeable-cation 

determinations for water-soluble constituents is 

essential. 

Parameters measured in the water-saturation 

extract for Sample A and Sample B (tables 10 and 11) 

exhibit wider observed ranges than those for Sample C 

and Sample D (tables 12 and 13}; however, relative to 

the absolute amounts of the parameters measured, the 

precision seems similar for Samples A, C and D. 

Sample B is an exception, and it also presented the 

greatest difficulties in the laboratory in determining 

when saturation criteria had been met. Perhaps, the 

data for Samples A, C, and D represent the maximum 

precision that can be expected for this method because 

of the subjective nature of the steps performed to 

produce a solution to analyze. 

Measurements of soil pH for all samples· show an 

observed range that is probably typical for this 

standard method of determination. 

15 

Hot-water-extractable boron was not detected in 

any of the reference samples and, therefore, the 

precision of the method could not be evaluated. 

However, analysis of an in-house standard used at the 

Wooster Agricultural Research Center, Wooster, Ohio 

(M. E. Watson, written commun., August 25, 1978} 

indicates that this method will probably provide 

acceptable precision and accuracy. 

SAMPLE-HOMOGENEITY ESTIMATES 

Total variation given for each paramter in tables 

6-9 contains two components: variation due to splitting 

(sample homogeneity, levels b-h} and variation due to 

the procedures necessary to obtain a measurement in 

the laboratory (analytical error, level a}. The 

geometric deviation reported for each parameter in 

tables 10-13 estimates the sum of this variation due to 

sample inhomogeneity and analytical error, while the 

geometric error is an estimate of only analytical 

error. Parameter variability resulting from only 

sample- inhomogeneity can be estimated in the 

following way: First, analytical error is removed from 

the geometric deviation by using the following 

equation: 

G Dn =antilog [(log G D~ - (log G E~ /z 

where GD is the geometric deviation with analytical 

error remgved and GD and GE are, respectively, the 

geometric deviations and geometric errors reported in 

tables 10-13. Then, 68.3 percent of the time an 

analysis of a sample for any parameter should range 

from GM/GD to GM • GDn on the basis of this 

estimate of ~ample inhomogeneity. This range in 

parameter values reflects an estimate of sample 

inhomogeneity. Similarly, 95.4 and 99.7 fercent of t1ze 

time the rang~ is estimated by3 GM/GDn to GM"GD.D , 

and GM/GDn to GM"GDn , respectively. For 

example, the 68 percent range for total Cu in Sample 

A (table 10} is from 11.1 to 16.8 with analytical error 

removed, the 95.4 percent range is from 9.0 to 20.8, 

and the 99.7 percent range is from 7.3 to 25.3. For 

DTPA-extractable Fe in this sample, the 68 percent 

range is from 14.6 to 16.4, the 95.4 percent range is 

from 13.8 to 17 .4, and the 99.7 percent range is from 

13.0 to 18.5. Figures 1 and 2, each containing the 

same area under the curve, illustrate the differences 

in inhomogeneity of these two elements for the same 

reference sample. From a comparison of these two · 

figures, the reference sample is clearly more 

homogeneous for DTPA-extractable Fe than for total 

Cu. From these figures Sample A is concluded to be a 

much better reference material for DTPA-extractable 

Fe than it is for total Cu on the basis of the estimates 

of homogeneity. Similar plots could be made for each 

parameter measured for each reference material by 

using the data in tables 10-13. These two parameters 

were chosen because, while they have about the same 

average content, they differ in homogeneity. The two 

figures also illustrate that the actual data tend to 

resemble a log-normal distribution but that not enough 

samples have been analyzed to graph the distribution 

accurately. 
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