Soil Mapping and Advisory Services

Botswana

SOIL TESTING PROCEDURES

FOR SOIL SURVEY

Part 2Laboratory Procedure Manual

44 UNITED NATIONS

ORGANIZATION OF THE

FOOD & AGRICULTURE

0 DEVELOPMENT

UNITED NATIONS 7431PROGRAMME

GABORONE, 1988

AG 801 85 011

FIELD DOCUMEN I 3

REPUBLIC CF

BOTSWANA

AG: BOT/85/011

Field Document 3

Soil Mapping and Advisory Services

Botswana

SOIL TESTING PROCEDURESFOR SOIL SURVEY

Part 2 : Laboratory Procedures Manual

by

Reinhard BreitbartFAO Expert

Food and Agricultural Organization Of The United NationsUnited Nations Development Programme

Gaborone, 1988

TABLE OF CONTENIN

SAMPLE RECEPTI()N, GRINDING AND STORAGE . . . . . . . . . . . . . . . . . . . . . 1

pH-DETERMINATION . . . . . . . ........ . . . . . . . . . . . . . . . . . . . . . . . . . 2Reagents . . . . . . . . . . . . . ..... . . . . . . . . . . . . . . . . . . . . . . . .

Equipment. . . . . ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... . 2Procedure...... . . . . . . . ............ . ..... . . . . . . . . . . . 2

SATURATED PASTE EXTRACT . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . 4

Reagent..... . . . . . . . . . . . ..... . ........ . . . . . . . . . . . . . . . . . 4Equipment......... . ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Preparation of saturated soil paste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Saturated paste extract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . 5

ELECTRICAL CONDUCTIVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Procedure . . . . . . . . ........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Calculations and data storage ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Temperature correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

SOLUBLE SALTS DETERMINATION . . . . . . . . . ..... . . . . . . . . . . . . . . . . . . 9Equipment, reagents and standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

PHOSPHORUS DETERMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Reagents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Extracting solution for Bray and Kurtz I . . . . . . . . . . . . . . . . . . . . . . . . 11

Extracting solution for Bray and Kurtz II . . . . . . . . . . . . . . . . . . . . . . 11

Color reagent A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Color reagent B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Standard solutions for calibration curve . . . . . . . . . . . . . . . . . . . . . . . . 12

Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Calculations . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

OR(;ANIC CARBON DETE1RMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Digestion solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Standard solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Supertloc 127 Flocculant solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

CEC-DETERMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Equipment. . . . . . . . . . . . . . . . . . . . . . . . ..... . . . . . . . . , . . . . . . 18Reagents. . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 normal, neutral ammonium acetate solution . . . . . . . . . . . . . . . . . . . . . . 18

1 normal, acidified potassium chloride solution . . . . . . . . . . . . . . . . . . . 18

4% boric acid solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Mixed indicator .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1950% sodium hydroxide solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Sulfuric or hydrochloric acid 0.01 n . . . . . . . . . . . . . . . . . . . . . . . . . . 20Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Calculations . . . . . . . . . . . . . . . . . . . . . . . . . ..... . . . . . . . . . . . 22

II

EXCHANGEABLE CATIONS DElERMINATION . . ..... . . . . . . . . . . . . . . . 23

Reagents. . . . . ....... . . . . . . . . . ...... . . . . . . . . . . . . . . . 23lnterelement effects during Ca and Mg determination . . . . . . . . . . . . . 23Preparation of Ca/Mg standard solutions (meq/litre) . . . . . . . . . . . . . . . . 24Preparation of K/Na standard solutions (meq/litre) . . . . . . . , . . . . 25Alternative K/Na standard solution in ppm ..... . . . . . . . . . . . . . . . 27Ca/Mg and K/Na with Atomic Absorption Spectrometer . . . . . . . . . . . . . . 28Preparation of the Varian AAl275 Atomic Absorption Spectrometer . . . . . 28Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31K/Na determination with 'CORNING 400' flamephotometer . . . . . . . . . . 3

PARTICLE SIZE DETERMINATION 33Equipment 33Reagents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Preparation of Solutions . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Pretreatment of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Procedure . . ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Calculations ..... . . . . . . . . . . . . . . . . . ..... . . . . . . . . . . , . . . . . 37

SAMPLE RECEPTION, GRINDIN(; AND STORA ;E

Sample reception:

Incoming samples must always be accompanied by a list of all sample numbers in the lot.Check the samples against this list immediately after arrival.

Report any irregularities to the soil chemist.

The soil chemist or a senior laboratory technician decide which laboratory numbers are to beassigned to the samples.

Record sample numbers and the respective lab numbers in the sample reception book andenter them into the computer data base.

Sample grinding:

Before grinding most samples first have to be dried.

Spread each sample on a tray, together with the sample bag and sample number card. Placein a wind protected spot until dry. Then till back into bag.

Write lab numbers on the sample containers with a permanent marker. Arrange sample bagsand sample containers in serial order to avoid any possibility of mixing up samples.

Fill an appropriate amount of soil from the sample bag into the 'llynucruste sample grinder.Alter about 1 minute switch oft Fill the tine earth fraction which has passed into the receiverthrough the 2 mm sieve at the bottom of the grinder into the sample container and discardthe reminder.

NOTE: Some samples, especially very clay rich samples, form extremely hard aggregates whendry. These aggregates cannot be grinded successfully with the Dynacrush grinder, they mighteven destroy it. Crush the aggregates first with a stone or a hammer before filling into thegrinder. Be careful not to crush any stones.

It no grinder is available crush the aggregates with u rounded piece of wood on a tlat trayand pass the soil through a 2 mm sieve.

Store the samples in the sample store room with incrementing lab numbers.

Reagents:

For pH-1120:

For pH-CaC12:

pH-DETERM1NATION

distilled water

0.01tn CaCI, solution

( 0.01m CaC12 = 1.11 g CaC12 per 1 litre or27.75 g CaCI, per 25 liters. )

Buffer solutions: Use pH 7-, pH 4-, pH 9.2-buffer tablets.Prepare according to instructions on the packet.

Equippient:

Two 25 litre drums for water and CaC12-solution.

One pll-meter with electrode. (Zeiss pH-meter 300 with plasticprotected 'Orion' electrode 91-55).

Two "AD 1-3 three volume one aliquot" dispensers.

Procedure:.

Switch the pll-meter in "stand by" position for warning up.

Of each sample weigh two times 20g into 100m1 plastic bottles. (One set of bottles is marked'pll-H20', the other 'pli-CaC12..)

To the samples in the bottles marked pH-1-120' add 50 ml H20 dist. with the dispenserconnected tu the water drum.

l'o the samples in the bottles marked 'pH-CaCI,' add 50 inl CaCI,-solution with the otherdispenser.

Close bottles tightly, put on shaker in horizontal position and shake for two hours. Aftershaking retnove samples from shaker and let stand for one hour.

Switch the pH-meter into 'measuring' mode.Place the electrode in the pll 7 buffer solution. Wait for stable reading.

(Less than 30 seconds should be required - if it takes much longer the electrode mightrequire cleaning.)

Set the meter to 7.00 with the calibration control.

Rinse the electrode with distilled water. Place it in the pH 4 buffer solution (for acid soils),respectively in the pH 9.2 buffer solution (for alkaline soils). Set the meter reading withthe slope control.

(The slope should be greater than 92% - if not the electrode might require cleaning.)

2

7. Alter calibration immerse electrode into upper part of sample suspension.

Do not stir the suspension.

Wait for a stable reading.

A change of 0.01 units in 10 seconds is considered a stable reading. Note the value,rinse theelectrode with distilled water from a wash bottle and continue with the next sample.

S. Alter pH4120 measurement also measure electrical conductivity of this extract.

(To decide whether or not preparation of saturated paste extracts for electric conductivit.and/or soluble salts determination is required.)

SATURATED PASTE EXTRAC'T

Reagent:distilled water

1(juif)ntenit:

24-place .hanical vacuum extractor cups for extractor.

large beakers (800-1000m1)

burctie (1(1(1 ml)

spatuLt

Prsparation of saturated soil paste:

Weigh 200 g of soil into beakers

With fly.' burette add few ml of water and mix with spatula.

Slowly add more water and mix until soil paste glistens as it reflects light, flows slig,htly whenthe container is tipped and the paste slides freely and clean off the spatula (for all soils butthe soils with high clay content).

4 tfft' mìxing allow Hie soil to stand for one hour or more. Then check satura criierizi

If Ow past,: stiffens or loses its glistening appearance remix svith water.

Free water should not collect on the surface. If the paste is too wet, add addithrwi

if soluble salts are to be determined record total amount of water and soil.

Cover beakers with watt], glasses and let stand for an appropriate time.

4

Saturated paste extract:

For conductivity determination the extraction can be nade a few minutes after preparing thesaturated paste.If the soil contains gypsum the conductivity can increase by 1 or 2 mS/cm upon standing.

Therefore it' gypsum is present allow the saturated paste to stand several hours (4-6 hours)before extracting the solution.

If the solution is to be analyzed for its chemical constituents, the saturated paste should standfor 12 hours or more (over night).

Place 9cm fine porous filter paper (i.e Whatman no 42,44 or 50) in extraction cups. Moistenwith few drops of water and press it on the bottom of cups.

Hang cups into extractor and connect syringes. Transfer samples into cups. Set extractor toabout 1 hour extraction time and start extraction.

5

ELECTRICAL CONDUCTIVITY

Procedure:

"Franskr saturated paste extract into small narrow vials. The cell constant of the conductivityelretrode, presently in use is 1.00. If other electrode is used check cell constant usually eitherengraved on electrode or on the connecting cable.

Switch the range of the Zeiss con 602 conductivity meter on 'cal' and set the display to 1000with the 'cal' knob (calibration of cell constant).

Record the temperature of the solutions.

Switch 'range' into the lowest of the three mS/m positions (do no use the p.S/m range).

Insert electrode into extract.

NOTE: The two platinum electrodes inside the measuring chamber must be completelyimmersed in the solution. If the extract is not enough prepare a new saturated paste extractof this sample and combine the two extracts. (this can happen with very clay rich soils).

Record the reading and continue with the next sample. If the conductivity is out of the setrange, indicated by display of (1. ) switch to a higher range.

There are rive range settings

0-2000 micro S/m

0-20.0() mS/m0-200.0 mS/m0-2000 mS/m

0-20.00 S/m

As already mentioned above only the three mS/m ranges (2-4) should be used.

II otherwise, it must be clearly indicated in the measuring protocol.Calculations and data storage:

Data are reported in mS/cm.

To convert mS/m to rnS/cm divide reading by 100.

mS/cm = mS/m/100.

6

Temperature correction:

Use temperature correction table to find correctimt factorFigure 1 page 7 (US. Salinity laboratory staff, 1954).

The correction factor also can be calculated with the formula:

corr. factor = 2.581+ (-0.493)*LOG (TENIP).

(Logarithmic regression curve calculated from temperature correction table.)

Soil survey data are calculated and stored with a Hewlett Packard HP 86B Micro computer.

7

Figure I Temperature correctilin table (US. Salinity Laborator Staff. 1954)

SOLUBLE SALTS DETERMINATION

Equipment, reagents and standards:

tiaiue equipttietit anti same cheinicals as for exchangeable ations

ornbined stock solutions:

200 ineq/1 t'a + 50 ineq/150 ineq/I K + 50 ineq/I Na

Prepare diluted stock solutions and standard series in the same vay as f.

determination, only that

the volumetric flasks are filled up with distilled water and not with ainioni; atCLli4 111114,'t,

PrOtled re:

l'ipette I nil saturated paste extract in to 0 oil volumetric flask up will: dc,ii111.:and shake well tu mix.

\ Olt: it absorbance readings of simples are too I,. ..1 tt 445 can hechosen.

The 'I, dilution' then is calculated:

Size of volumetric flask : nil saturated paste extract

Further procedure is exactly as for exchangeable

Calculations:

If linear regression curve is calculated concentration C of soluble cations in ntc:tsioring sointion is:

C =- a * E + b

a, b = regression coefficientsE = Extinction (absorbance reading')If no linear regression curve is calculated concentration C ot° soluble cations in measuring solutionis:

E / e

E Extinction (absorbance reading)e = Extinction coefficient

e is calculated from standard curve:

e = (El/Cl E2/C2 + E3/C3 + + En/Cn)

El, E2, E3, En = Absorbance readings of standardsCl, C2, C3, CI( = Concentrations of standards

= Number uf standards

4)

Concentration I: of soluble salts in soil Imeq/11

K C ext rac: .

:11); Soil ] is:

C

iit': II ,t2ti FOE 1)0.1A

Seigio s(+il uscii to/ ,

(Million -= i hut cTrait 110 rctsk)2 (ItItkiimi

2.dilution / 10

PHOSPHORUS DETERMINTION(Bray and Kurtz 18e11,1

11

`1`wo 25 litre drums for extracting solotim:

\lulti-tunnel rack for 33 funnels ot appywk ,6.aineter.

Vi'ter paper 1Vhatman 44 or 42, 9 cm

Brinkman eolorimeter PC 600 'dip in' pi-obi'o an othcrooloinneter, preleisthl.$ Nvitk Stoll threngit cet!

( niNO 1.. N111(1ti: one d1iql1<it iii'i orinc( -11) volono thrkk olionot'urn

One SCD 1 ". lion dilute!.

One multisamTm. stirrer

klM11011 FlUoride N1141 ,A11,

Hydrochloric add kola 101NII,Mo,t),, 111,i)

kotimon)-Potassium-tartrate K(ShOit 41140,,l1 510Sulfuric acid conc. (98(,iAscorbic acidPotassium-dihydrogen phosphate 1(1-1,PO4

Er solution for Bray and Kurtz I:

0.03 in NH41. irs fICI

Dissolve 27.78 g NI-14F in approximately 500 ml distilled/deionized ateu dd 53.6 nil 11C1

(36%). Dilute to 1 litre in volumetric: flask, dilute to 25 liters in (from I)) 'adding 24distilled/deionized vitter with measuring cylinders.Close the drum and mix thoroughly.

Extracting solution for Bray and Kurtz U:

0.03 m NII,F in 0.1 in HC1

To time dissolved 27.78 g NH,F add 214.5 ad WTI cone. (36%).

Proceed as above.

real.:( it4

Ot .

01)1)1'0\1111;1ft ur 33 samples plui, stiaidal-os is 250

,olotion eus ,tik tor one day and has to be prepared new just be"

ara saluaons for calibration curve:

Stock solution . 000 ppm ['Nitre:

Dry Potassium-dihydrogen-phosphate at 80° Celsius in an oven,

ool in a desiccator,

Weip211 1.393 g and dissolve in 1000 nil volumetric flask with distilled water.

. Diluted stock solidi° :

100 plan P/1:

Pipette 50 ail of 1000 ppm stock solution into 500 nil volumetric Ilask. Fill withdistilled water until about 1 cm below mark. Temperate tu 20° Celsius in waterbathand till up to mark.

10 ppm P/1

Pipette 50 ml of 100 ppm solution into 500 ml volumetric llask.

Proceed as above.

1."

telor reagent A:

I. Dissole in a beaker 30 Aintrionintn-hepta-molybdat. in about 250 int 1190 dist.

Dksoke in a SeC0116 th'zti,Cr 0.727 g Antinomy- Potassium- tartrate.

Fill about 500m1 112(di. into a 2000m1 volumetric flask.

Add slowly 340 nil conc. 11.2SO4.

Cool in a waterbath to 200 Celsius.

Transfer Molybdate and 'Tartrate solutions,

Fill up to the mark vitli distilled water and transfri- into 5 litre bottle,

Fine mid 3 liters distilled well

9

3. Standard series:

Pipette

10, 20, 30, 40, 50 ml

of the 10 ppm solution into 500 ml volumetric Bask.

Proceed as above.

l'he resulting standard series has the concentrations:02, 0.4, 0.6, 0.8, 1.0 ppm P/I

Settint:

A soil/extractant ratio of 1:7 is used.

Set Me dispenser for the extractant to 35ml. Using a AD 3 'three volumiit must be made sure that all three syringes dispense precisel) the same

-.three aliquut.dispenseltune.

13

Set the SUD 1 'combination diluter-dispenser' to dispense Sinl cok,7 15dul (list, water andtake u 01,11 extract.

'nit resulting dilution of 1:2 for samples and standards is found convenientAsorlIanee for the highest standard is around 0.2-0.25.

Procedure:

1, Prepare the multi funnel rack. Fold double layers of filter paper and staple the edges thathold their form. Put the titters into the funnels and place a tray of 33 bottles under the rack.

Prepare the color reagent 13. For one batch take 250-300m1 of reageo: Add 2.5-3 g Ascorbicacid and stir with a magnetic stirrer until dissolved.

NOTE: Color reagent B is stable only for a t'ew hours and must always be prepared justbefore the determination.

Weigh 5 g of the samples into the bottles of a tray. The last sample should be a standard!sample which is repeated with every batch.

)iiiekly dispense 35 ml extracting solution to each of the samples.

Sdir for 1 minute with the multisample stirrer. (If the Bray and Kurtz II extraetant is usedstir for 40 seconds.)

Immediately after stirring filter by pouring simultaneously the contents of 1 1 bottles (onebottle rack) onto one row of filters. It' the filtrates are not clear, filter again using the samefilters.

Put the tube connected to the syringe calibrated to 5 ml of the combination diluter-dispenserinto the color reagent B solution. (The syringe calibrated to 15 ml is permanently connectedwith the water drum.) Pump at least 5 or more times and discard solution to make sure thatall tubes are filled with fresh solution.

S. Plao third bottle rack tras next tu the one with the tiltrates, Put tire double plastic tips uftitc diluter-dispenser into eXtract. By pressing the lever take up 20 nd extract, 5 nil colorreagent and 15 ml water. Transfer this into the bottles of the third tray by run asing the lever.l/ip the tips rIi t beaker with distilled water to clean the outside.

For the standards proceed vay. Eill a little wore tiran 20 ml Of tire stttiidards andextracting solution t r the V of bottles and transfer with the diluter penseritrio a econd ro','.

\TNT 1101(1, (0 1 hour the blue color of the mthe spe-trophotometer determine the absorptionw.;.% etengttL 1. Want°. fl11. Zen).

fhis stan 1;11 1111.111R:11 1 ille relatively phosphorns-poor soils mostxceptions 4(i u0h:t 1) I diluter: he P-concentration is 4eileral t."

e slatit 1140! should be changed.

Calculations.

Concentration C of P in solution is:

I t on coetlicient

The [slim nun coefficient is kalculated standardroncentratioi r uf the standards is known Extincti is read from tire spectr

E3 C

El F2. En = Extinction uf standard 1, 2, 3,..., ncentration of standard 1, 2, 3,..., nmber of standards

ulated:

n Extract r Weigh

NOTE: \\Atli dilution is not the initial dilution with the diluter-dispenser meant because [Itere thestandards are diluted too.

,bdate cmnplex is fu 11v developedstandards and sato ples at 661 1101

data is done Ivith tire Hewlett

in ppin P is cal ut.tted

14

...11C111:11101:, ..,101¡;11.1 printingmierc11. thk r1,11 iied the concentra

,

1,7 0): ,Z'

Digestion so ut

Sodinin tlichroinal

t5

Standartt

iII 100 tul VOIU o

1.1iwculant .olution

superiloi 12- il,IC uit.t tcie,ltt 1)ívl\ltlssid. It IS highly( ft(Iilt,Ill tul Itil, neon-,11 and

1 gram per 10 liters of soluti

ss.11

I 11'4 prl'ILIT1 t.11111Ct 110 11)0)1 mi beaker. Stii UI iuul ot 55111cr i,ith a magneticstirI VI 1/1 111111 ,1 1)11`,

oii ;ter (: ('are nit taken II) 1)11.'NUnt

to, lug Wilt II, dis

sin el it . 111101 imiiwccio 01 Ow !,tilv, titi i lot tutti 110, t1iit lt 511110 VC(1 :ilatiinì P'

-

- dis (n.ei 1( 'fflanttu 2 inl- 11n SI) 1 diluter to ol

OilitItt lit-f....

4, lint ttofit

ditt, ,.(11k11 6111,

\tttu ì)!ninon-111t.

flour f;...(t ttllr

tiertliic 127 /loci 111:int silin ion

di iddon

ur (hlOlen, link

Pipette t,11

oni tuiptil loci is II oi

Glut

1 in

NOTE:

= > 2.50g gluco-: Ig

= > 0.0Ig ( 100 1g 1.00 rcum

1.0, 2.0, 3.0, 4.0, 6.0 % org. C

,or aiiirÌeswith more than 6% tog (' different itple dry, 'hod)must be applied,

Vith th tet aliquot from liw 'lcar supernatant solution arid transtcr Ottea bottle of tue bottl& ;trefoil% not ,tir tire sediment.) .Iso tratislet shiiid,iiiI,ui(1 Wane.

\leasure absorba rice ith a lirinkman colorimeter or all i,rtwith flow through cel at 570 tun.

culations:

- Soil Survc (-Mahon acc.-cattiputcr,

\ hen I g veighed the standard tc-c -o,.,-esponds w tin

0.50, I % org.

II the g.C exceeds - be repeated wOh O

corres ids then

r\utottlalic 'tractor, 24 pl:u. ucept Enghieeriiigjnc.

ksak-p,sablc,polyprop\lene,6k1 1111,"s1onoject' rescikoirI, hi into "Sample syringes

(Mom!, (lit III itilli (milicctutg sliingi 1

1oalytic:II tilr p Le. aiol Schoen, No..7.8(khcal sims kr. ou1 or iished

1..jcitee unit w

,\uit&ituitttc iII a lt unit

)igestion tiMes. 2511 nilConical Flasks. 2511 nil

oltimetro: flasks 10i1 1111

Reagents:

Volotoolow\ceto acidXmoomi:t ,olOtioohoric ;1C1d' odiOto 11,ydroicie flake,

ohitlietric solution kit sidliiroEthanol 95() (methylated spiricEthanol 50`k (methylated spir0;Pluassitun chlorideHvilrochloric acid ()%

I -1)1.TERMINATI

ydrochlock'

\ k I

.1 normal, neutral ammonium acetate solution:

Dissolve 1926.8 g ammonium tietutu io 5 liters (listilled water.

\Lilo.- up tu 25 liteis

Wilc,1 pH to 7.0 with either lCeit, acid kil IIIiIIIIUia solution if p <-

1 norrnak acidified potassium chloride solution:

Dissilhe !Sol," g potassium chloride iimakiRai ad 5 1 distilled %atec,

Add 125 nil 36% Hydrochloric acid.

Nlals: )1) to 25 L

dd

fleat it, near boiling and stir until dissolved.

I rawder through a large polyethylene funnel i,t 5 \ rt. it% RIt uttiti2- liters of distilled ssater.

Add a few nil of iiidictor' and Illakt' t.' liters.

Mixed indicator:

Dissolve0.5 g res.)! green

and 0,1 g h1ìrtli t.('

in WO tul 95% alcohol

5W; stuliwt; tivitroxide solotion:

20

A ifoo: ;a a 5 litre beaker,

arviidiv deionized ij to it volume of 5000 nit.

hssoieti and

st1r:o2c taU ti Kjcitc: 10;,. has 10 liters

frf IMO' ill I )110.1I11 and goggles are imperative!

Sulfuric nr hydrochloric acid 0.01 n

Mute moltnadric solution accordinuf

( N'0111111VI SOlUtI01, IS I normal pipette 10 nil into 1 I volumetric flask and till v.ithwater to about cm below time marl.. Put flask iii Nvaterbath temperate al 20°C for 3f, minutes.Then till lo Mark.

Procedure:

1. Prepare sample extraction tubes by placing approxiii g 0 litter p u I p formed in to a hain a syrirt:;:. harrel.

Force it down tightly with plunger.

Weigh 2.5 g of soil sample. It' sample is rich in clay and/or salirme, inix well with one 10 nilscoop sand Or edite. Fill mixture into tube.

NO'FF: A blank should be prepared with every batch. This is imperative if samples have beenmixed with sand or edite because both adsorb a certain amount of ammonim» which mustbe subtracted from time result.

Place sample tubes in upper disk of extractor and connect tu inverted syringe. The plunger ofthis syringe is inserted in slot of stationary disk Of extractor.

Fill sample tu he to the 15 itil mark with al11111011IUM acetate. Stir carefully to release allenclosed air bubbles from the sample. Rinse the stirring rod and the sides of time tube withammonium acetate from a wash bottle not exceeding the 25 inI mark.

Set extractor to 2 hours extracting time.

Add about 45 nil ammonium acetate solution to reservoir tube, start extractor.

At the end of extraction the extractor stops automatically by a micro switch. Switchoff and pull plungers down as far as extractor will alloW.

Disconnect syringes from sample tubes (leaving (libber connector on Sanijile tubtfland fillcontents into numbered 100 ml volumetric flasks.

Fill syringes again tu 35-45 nil with ammonium acetate solution from a beaker ¡toil till alsoimito volumetric flask. Fill up to volume with aminonium acetate from a wash bottle. Nlix well.

Keep for exchangeable cations determination.

Return upper 2-disc unit tu starting position.

\ttaih io sample tubes ,-11)e sides town. . 1, ethanol. fill .. marl.

1 lac e r1LO,abes in sample tidies. Fill t aluilit 4-z .111 mark01 ethanol shoul(i bc justt ittle less .;liati ti 11.

'1/41Icr c\ULIOU stofiped !urn it off., pull plung!. 77 (10%u, 1211)11 Andt 'AMMO VaSill.

21

15. ib s)rifles with acidified 1 in potassium chloride solution and estrai.l. Collect eslract insultintetric flasks. Fill up to inark vv oh potassium chloride soliition mid shake N/A tO

I'll/01V I 50 ml aliquod KCI extract digestion tul)es.

16, Remove sitinple tubes and transfer samples lo the digestion tohes ot the distilling unit.

Fill 25 nil or the boric acid ,ilotom into 250 tol coin,.

^witcli distillitig unit on.

Place an empty digestion tube and a beaker in position.

(lose valve of steam generator outlet at the haek Id the (milOpen steam salse. Open tap until water level reaches the electrodes in steam generator Closetap.

When water starts boiling upen lap again. Regulate %vale,' current that the bin:knowing water(coming from condenser as cooling Nvater) is just hand warm ;4-5 liters per minute,.

Distill about 150 nil into beaker. Close steam valve.

Place tithe with first sample and First conical flask with bori, acid in positi,,i, \aid 51)%sodium livilroxide solution by puling; the lever of the 'alkali moor'

()pen steam valve and distill 4-5 minutes coiieet 125-150 nil Clo.m: steam salve.Remove tu be and conical flask.

2(). Place tube with new sample and new conical flask in position. Add sodium hydroxide, upensteam valvc,

During second distillation Wrote first sample vvith 0.01 nD2S0, or 1 and so on.

At tire endpoint of the titration the green color disappears completely. lile solution looks greOne drop more gives pink. (If an automatic titrator is used, set the end point to pli 1.4»

z

( t tr4ct/a1iquot

Lai :1Ifl 11!,C(.1 for titrationI) nit blaitc titration

oormaiify of acid ( (1.)riAtrait = Intl nitNviglit

'uiI=- (1-1))*(.1.01'''100125 101151.

cic ime/100g soil] = (t-b) 0.8

t

.11r,1" pro

iiUt ineasurint;solutions

EXCHANGEABLE CA IONS DETERM NAT N

Equipment:

olunietric flasksSD-1 diluterSO nil polyethylene cont,iiiier, ,ir

Absorptioa

lical);Nii is,

11 01111111M id oridu- 66.6: 11%, Ni --- ti:' 6:LaittimIllimcilloride 71 ;INV =371.1" kVil-1, .)-- ! 38..1 i

,...aleinmeartionate L. at'('), 'WO) =100.09\ laguesininsulfateNIg0S, '7 .,( Ws. )=.2-16,-ISSialiiiinchloride Na'Cl ' \IA% .7=5:i.-14l'otassiumeliloi ide Kti

erneut cts during Ca and Mg deter ation.

to aluminuni and silicon and iotlizito,i, , on 1 i o the Ilium iiiii.),10

tictet'uttiiiation, Ionization otMini» ric, o y 1 ,doittionni ii) th,red in. ell by addiuig strontinio spei....i..),.iY I intb Aile l i ii,mitat

1(K) ppna Sr or La concentitct s1ncl Notation

Dis,,.(11 SrC12*(41.,0 in 5 liters dist, water, Foi s,. it

St '611,( Sr)

or

dissonc I 338,7 g LitC13*711"0 in 5 liters dist. water. (For better solubilityEaC1,'7(10 37.-rf) La)

2000 pion working solution

stock solution 5 I 1

distilled water,

or

Preparation or ( standard solutions

Comb:soli ,toek, solution 200meti/1 Ca + 50ineti/1 1k1g

Dry CaC() ;yid N1,..,.'+(14!*7112i.) di 100° Celsius in drying oven,

f 0.090 Cir('()anii 6 It): 7H

40.0 a 1;1 VOIllinetrie

1.:11 -t. ball' %vial ,.LH

, Ma: carbonate.

121,ri1f)er8ttire ;,. (' in

'Ow ionics mark! and slii velL

Diluted CMg stock solution 1:5)

!'ipt.ti; lutiw: into 500 11 vokimetric flask,

1111 lo about 2 cm bch,w unia. lAith 1 n .annionisiwOrion ( ileterrinuit ion),

tempt.::-;ilor% ; in \!1

up tu stoppe; tsk and shake. vell.

Tit:, so ;1; coutiiny,

40 meg Ca/1 and 10 meg Mg/1.

!. kndard series

5, 10, 20, Sc; ml

'OJllti1)fl nito 100 nil volumetric flas;,,

Fill to about 1 cm below the mark with 1 u ammonium acetate solution,

Adjust. temperature tu 20° C in waterbath,

After 30 minutes till up tu mark, stopper flasks and shake we

24

t`10,"1110

--t;3;3;1.irti 2 ineti : 3 tic 3

4 met! /

-0:111(1.itti 113eq intii I !

4. ....+Lttitlarti Ili wet} ! 2.5 101,.`1,1 !

3, fauIird 211 iti / ti intAi I

ratyon of K/Na standard Nolu tly

i,31.3(1/1 K

VW lip to ;Wont ent heit)%k ¡mirk SSitlltIt+sitter.,

'e 21C

--)pper

Store

01111iVO

ItOt Ottll Olt Intl) 5t10II I ii iiitiiiitiii,ii,i11.141t( WWI( (-Et Fit loaf lop

C in

Fir ;mil- 30 13-3

t solution Loot .... ,

2 rnt

25

\iternative K/Na standard solution in ppiii:

Combind stock solution 2000 mini k plan Na

Weigh 3.8133 g KC!and 0.6355 u. NaCI

hit() 1000

1 \ 11)11(%

I)iluted stock St1111i1011

Piocilc _ill la

The solution contains;

npin K anti 2:: :;p1

Proceed as

The Nonni/ins contain:1, Standard

StandardStandardStandard

5, Standard

Standard series

Pipette;

5, 10, 15, 20 50 nil

stock solution intr. 200 ini 011,1111CtriC

5 prim K 0.625 ppin10 mini K 1.25 mini Na15 ppin K 1.875 ppin20 mini K i 2.5 ppin N;;50 K 6.25 pion Na

Cit/Myld K/Na with Atomic Absorption Spectrometer:

lo order lo avoid too high absorbencies dilute samples and standards:

Ca/Mg-determination by factor 50K /Na-determination by factor 10

Connect the SI)-1 diluter set to a dilution ratio of 1:50 to the 2000 ppm lanthanum chloridesolution. (1 ntI sample uptake + 49 inl dispension.)

Connect the diluter set to a ratio of 1:10 to a drum with (I°, died water. (5 ml sample uptake +15 inl water.)

lit the literature a 1000 ppin cesium chloride solution is recommended to sup ss partialionization of K and Na, Tests showed that the etree: lies within the erroi range ol thedetermination. The costs tot the er3 expensive chentii,il pu n- cesium chloride can lw save&

Dilute ammonium acetate extracts from the CE( deternuir.,;1011 and standards inti»o yethlenecontainers. For blanc dilute ammonium acetate solution. Sv -ontainers tr mix Then 1111 olutioninto vials Milne, the automatic sample changer.

Preparation uf lhit Varian ,lA/27.:. Atomic Absorption S

setttag ot a('ehlene ga, pressure

SioNvi:, open tti:tip Oinzft:;

b. Check that iman pressure is inorc than 700 kpa II piessori. is bt...ioobecause acetone ma be formed and can come into the sstent.z

c Check that gas pressure olto svsleo:not get started!

2. ()iterating_ modes:

The Varian Atomic Absorption Spectrometer can be operated in se'

Fully automatic with automatic sample changer and the t icwlc t 11.118613 microcomputer as controller and receker of the dal::

Half automatic without sample changer but controlling and ,andling by thecomputer.

Half autotnatic with sample changer but without computer.

Manual without sample changer and computer.

28

a. Full automatic operating mode:

Switch system on in the following sequence:

I, Uninterruptable power supplySpectrometerCompressor and exhaust fanSample changerPrinter (make sure that printer is connected to .p ectr4otteter and not to eomputerMonitorDisc driveInsert I-IP86 AI275 - system disc into drive O and datitsk into drive i

computer

I lic Ainostart' program %will start up computer. Forlisplayed on monitor.

Index' section

7,istrumer

Set: t '3 -waNcleligtil 422,6 toolMg-wavelength '285.2 Diu.I. -wavelength i "O) 5 ii in i

\a-viaveiengt li ..t.s9.0 mu k

NcylT. at must be clnel. ' .7

l.ntei: stion 'Do you tvant atit,, set op'''.Enter 'I' ti) inn.e recommended standard settings for ,pcOrometvcproglarnmed, (In this prograinnw tile Iseyboards ,peoromocrare unlocked so that hndh could also I.e lo

Recommended standard settings:

Spectrometer: Sample

(wingerorple

29

Continue following instructions displayed on monitor,

Press 'FLAME ON', Flame must be light blue to colorless oith a sharp hih hlue rim at turburner. If there are edges in the flame switch off and clean burner slit with a brass Made

Check whether highest standard is within measuring range. It' not, tilt hornef until needlemoves imito leftmost field of peakmeter. (This is necessary for Magnesium misìmn II conilmictlCa/Mg-standards).

Start automatic run. The end of a 11111 is signalled by a centiiimitis beep from thespectrometer. The system automatically resets. 'reoart: determination :)r.. next

NOTE: The setting of the system parameters does not have tu be repeated. Press 'N' or'Spacebar' at time question in the 'Optimize Instrument' section.

After determination of all elements go to 'Master Index' section. Press '6' (transfer dataprogramm) to transfer the data into the soil survey data base.

Lamp I (Ca/Mg) : 5 inA No. stand:it 5

Lamp 2 (K ¡Na) : IO ntA Rinse rate 0

Integration time: I sec Rinse time 5

Absorbance mode (ABS)Del thin f

4Integration hold Iteslope rate : 6

Half automatic (wet, IIOUt

'I he saint ,=)ib1i11,T which controls the full automatic operiautomatic mode without sample changer. Time setting of the smanualk or by software using the same recommended param

spect

Loni sample changer with

'Start' to start run.

Manual operalito qd sample changer:

but with uoiui r as cou tt. .mode alSO handles

nneterabokc.

r, hand. thu ruath.ogs press 'Spacebar', to proceed to next sample press'CON1'

Transfr data into soil survey data base the same way as abo

i ir ;ottoman( opt-, ,thout cotnptc;k, ;.; .

changer is in 'Auto sample' !MAC at SingkS111111,4 modc,

Loop through pzirameters nressing repeatedly Programin set up', change parametersusing numeric he hoard.

irameters. (Spectrometer must be in 'AliS'-niode.)

OFit'r;t1i0;,. iety of measuring modes:

Headings ¡ire diSpkIed and printed &Abe wbance to it ncentration in,Idt. 16concentration mode Irds are al rom %%hid,' the con(euItraIiIuuI ot tIttsamples is calculated,

The samples are measured either in 'Integration hold' or in ' mode In'integration hold' tunde impulses are integrated over a 'Certain set time, In 'run mean'mode an accumulative mean is calculated of readings taken between start reading andpressing the 'read' ko a second time to end.

information refer to the operating handbook for the spectrometer,

oliwnsloit of standards is : ineg I liter

ie concentration C in megll of in! elcm,?rit in a sample k:

C e

ENtinction (alkorptimue = Extinction coullimot

:al nl from time standard cur.t:-.

(EL/Cl

E1, E2, E3, ... En = eklisorbancc readings 0! ,,tandarilsCl, (Z2, C3, = f;oncentrations of standards

= Number ot stantlard,

rhe cor..T; K of a sample in 100 g sci! 's:

K =

Extrao = 100 ml11eivli1 =- 2.5 g

K = * dimwit!

Calculations:

ill tst. o1iilkoehericies have iieen measuivil and no linear !egression eve Or till ,`11:1,1!

e kkulated i.oncentrations III ineq/100 g are calintated atoll.os:

KiNa determination with 'CORNING a ephotometer

IR t'iiiO,iII1iconcentration rebajon i, linear only upa certain concentration. Therefore it is advisable to dilute samples and standards for the

potassium determination by factor 5.

Ube corkentr:ition of the Na-standards is low enough to stay in the linear range of theentissioniciincentration function.

Set the S1)-1 diluter to a dilution ratio of 1:5 (8 tul solution + 32 ml dist. water).

1, For I.-determination dilute ammonium acetate extracts from CEC'.id!Ida rd imito plastic container,. For blanc dilute ammonium acetate solution,

For Nadctermination transfer some of time extracts and standards without dilution into thecontainers. Foi blaiic use undiluted ammonium acetate solution,

Switch p.,.,.er on of the Corning 400 tlamephotometer.

Open th,. i.ta tap. Switch 'Fuel - on'. ()pen window to the burner chamber and pressuntil llame is burning.

Set the filter t 'K' (for potassium).

1. Insert tiibt: into Mane and set to O wtth 'blanc' regulator. Then insert 1u1ic into higheststaliday-f. and set to 100 with '5ensqivit3 - coarse - tine'. Repeat Wane setting, repeal sensitivitysetting until reading,- arc constant.

7, \l:uir stwdirit curve, then measure samples. Record, tite values on the appropriate form.

8. NV hen all samples are determined set filter to 'Na' (for sodium) and Catibrak he instrumenl.as above f.point Nleasure standard curve and samples und record the

9, For ch. - g down first cios;., gas tap, then switch 'fuel - otr, then 'power-ofr

PARTICLE SIZE DETER N

o quipment

1000 nil beakerswatch glasses fitting beakersrubber policemen for cleaning beakers1000 ml plastic bottles with tight closing lidDispenser for hydrogenperoxideDispenser for Na-hexa-meta-phosphate solution1000 ml measuring cylinders without spoutStopper to close cylindersSoil hydrometer(s)

kVaterinith with thermostat controlled cooler/heater

Centrifuge equipped to handle samples up to 1000 ml

Sample shaker

Stopwatch

Sieves 53, 106, 250, 500, 1000Sieve 53 p..m for wet sievingSieve shakerSoft brushes for cleaning sieves12 paper with smooth surface

2-decimal place balance

iteATAB:

.'.;,oclititn acetate NaC21-1302*3H20Acetic acid glacial CH,-COOH

Hydrogenperoxide 30% F1,02

Sodium citrate Na.,C61-1,07*2H20Sodium-bi-carbonate NAICO,Sodium-di-thionite Nzt2S204Sodium chloride NaelAcetone

Sodiu -1exa-metaphosphate (NaP03)6Sodium carbonate Na,CO3

Prcparation of Solutions:

Solutions for pretre. of sa pies:

1 normal sodium acetate solution pH 5.0:

Dissoke 3400 g sodium acetate and dilute to 25 liters in drum. Adjust to pH 5.0 with aceticacid.

03 normal sodium citrate solution:

Dissolve 1305 g sodium citrate and dilute to 25 litres in drum.

1 normal sodium-bi-carbonate solution:

Dissolve 2100 g sodium-bi-carbonate and dilute to 25 liters in drum.

Solution for dispersion of soil samples:

Sodium-hexa-metapbosphate solution:

Mix 135 g dry sodium-hexa-metaphosphate with 35 g sodium carbonate powder in 5000 mlbeaker. Fill up with water and stirr until dissolved. Then transfer into storage bottle.

Pretreatment of Samples:

NOTE: Removal of carbonates and free iron-oxides is optional.

Removal of carbonates (if present):(pH >6.8)

Weigh depending on the clay contents 50-100 g soil into 800 ml beaker.

Add 250 -500 ml 1 n Na-acetate solution.

Heat on water bath to boiling. After effervescence has stopped, add increments of about 25 mluntil it does not recur anymore.

(In case of very high carbonate contents 5 ml increments of glacial acetic acid can be usedinstead of buffer. In this case monitor the pH with indicator paper.)

Add 500 ini of water and add a few ml saturated NaCI solution for precipitation.

Let stand over-night and siphon off or centrifuge.

34

Removal of soluble salts:

pH>8.2 EC> 4 mS/cm (400 mS/m)

If no carbonates are present but the electrical conductivity exceeds 4 rnSicm, respec ve %

InSim soluble salts should be washed out:

Add approximately 200 ml Water to the samples, let stand for about two hours, stiroccasionally.

For precipitation add few ml saturated sodium chloride solution or acetone.

Centrifuge excess water, then continue with normal procedure.

Oxidation of organic matter:

Only if the org.0 contents is bitmer than 03 % organic matter most bc removed.

Add 15 ml water and 15 ml of H202 (30%) (In case of buffer pretreatment less or tr,need to be added). Let stand for 1 or 2 hours.

Place on hotplate and warm to about 50° Celsius.

Add small increments (5-10 ml) of 30% hydrogen peroxide until decomposition of orgamatter is completed.

NOTE: Too strong frothing can be tempered by removing from hotplate (cooling t.

water) or adding few drops of alcohol.

In general supernatant solution looks clear after decomposition ,of rgauic matter.

To remove the remaining hydrogen peroxide add about 300 ml or water and boil until thevolume is reduced to about 100 ml.

If no iron coatings are to be removed, transfer samples into shaking bottles.

Removal of iron oxides:

Add 500 ml 0.3 n Na-citrate and 70 ml 1 n Na-bicarbonate solution.

Warm the suspension to 80° Celsius then add 2-10 ml scoops of solid sodium-di-thionite.

Stir suspension constantly for 1 minute and occasionally for 15 minutes. (Avoid heating above80° Celsius because iron sulfite (FeS) forms.)

Add 50 ml saturated NaCl solution to flocculate.

(If suspension fails to flocculate, add 50 ml acetone.)

Siphon supernatant solution or centrifuge.

Wash with Na-citrate (add NaCl or acetone if necessary for flocculation.)

Siphon or centrifuge again, then transfer samples into shaking bottles.

35

Procedure:

Dispersion of soil particles:

After transferring samples into 1 I shaking bottles add 50 ml sodium-hexametaphosphatesolution. Make up volume to about 400 ml to 500 ml with water. (Shaking bottles must be halt'fall to ensure proper dispersion.Do not over 1111.)

Pat samples on shaker and shake for about 16 hours (overnight) at a speed of about 125strokes per minute.

Clay and silt determination by hydrometer method:

Transfer samples quantitatively t'rom shaking bottles into 1 1 measuring cylinders. Fill up to1 I with water and place in water bath temperate to 200 Celsius. Let stand for about 30minutes to 1 hour to equilibrate temperature.

Take hydrometer readings for a particular sample after:

40 seconds, 4 minutes, 4 hours

Close the first cylinder with rubber stopper. Shake vigorously end over end for about 1 minute.Make sure that the sample is completely dispersed.

Put cylinder back into waterbath, start stopwatch insert hydrometer carefully take 1. readingafter 41) Sec

('lose second cylinder, shake and put back into waterbath after precisely 2 min total time onstopwatch. Insert hydrometer and read after 2 min 40 sec total time.

Wait until 4 min take 2. reading of 1. sample. Wait until 6 min take 2. reading of secondsample. During waiting shake third cylinder already. Put cylinder back into the bath after 8min total time. Take 1. rea-ding after 8 ruin 40 sec.

Shake fourth cylinder and insert at 10 min, read at 10 min 40 sec, wait until 12 min, take2. reading of third sample ,wait until 14 mm, take 2. reading of fourth sample, and so on.

Take the third reading after 4 hours settling time.

Starting I reading times for 24 samples see table 2.3.

Separation of sand fraction from clay and silt:

Place a 53 micron test sieve in a large funnel into a sink equipped with a 'soil trap' to avoidblockage of the drainage pipes.

Transfer sample from ineasuring cylinder on to sieve and rinse thoroughly with water until allclay and silt fraction is washed out. (The water jet should not be too strong to avoid lossof sand fraction due to splashing).

Wash sand fraction from sieve into beaker.

Place beaker on hot plate or drying oven to evaporate water.

36

4. Dry sieving of sand fraction:

Stack five test sieves 53, 106, 250, 500, 1000 p.m meshsize and a receiver pan.

Transfer sand fraction onto the top sieve (1000 p.m) and put onto sieve shaker.

Shake for about 5 min at an amplitude of 2.5-3 (amplitude scale is on sieve head).

Brush the fractions on separate large sheets of paper with smooth surface.

Clean sieves thoroughly.

(Do not use brass or steel brushes for sieves with nteshsize smaller than 500 micron).

Tare beaker then add fractions starting with receiver, then 53 jun. I:4;

Record each weight.

Lalculittions:

Sand Fraction:

weight% or fraction = weight of fraction x 100 !total :Tight

Total % sand = sum weight% of all sand fractiw,

(receiver fraction is considered coarse silt !)

Clay and silt fraction:

Corrected reading = reading - blank + (temp-20) * 0.36

(Temperature correction: 036 is an empiric factor used in literature. Since temperafili ewaterbath is kept at 20° Celsius, temperature correction is 0).

(Total clay + silt.) % = 1. corr reading * 100

A correction factor can be calculated to make:

% Sand + % clay + % silt = 100 %

Let: SS = % sand from sievingHY = (clay + silt) % + weight % of receiver fraction

Corr. factor = (100 - SS) / UY

37

weight 53 jt fraction = Nye ight 53 - receiverweight 106 j fraction = weight 106 - weight 53weight 250 p, fi-action = weight 250 - weight 10(weight 500 p. fraction = weight 500 - weight 250weight 1000 p. fraction = weight 1000 - weight 500

This correction factor is based on the assumption that the determination of the sand fraction bysieving is 'correct', no sand is lost during the procedures. It equalizes minor reading or roundingerrors since it is difficult to read a hydrometer more precisely than one unit.lf no soil hydrometers,calibrated in g soil / liter are available, only hydrometers calibrated in specific gravity (g / liter)the factor corrects the readings to % soil.

The correction factor using soil hydrometers should be in the range of 0.9 to 1.1,

- with hydrometers calibrated in specific gravity in the range of 1.71 to 1.75.

Values outside this range indicate errors in the determination.

Let: crl = 1. corrected reading (40 seconds)cr2 = 2. corrected reading ( 4 minutes)cr3 = 3. corrected reading ( 4 hours)wt = sample weightwtr = weight % receiver fraction

% coarse silt = (wtr + (crl - cr2) * 100 / wt) * corr. factor.

% line silt = (cr2 - cr3) * 100 / wt * comfactor

% clay = cr3 * 100 / wt * corr. factor

38

Table 2: Time table for hydrometer readings

Start stopwatchTime : 0:00'00" hr:min'sec"

Sample 5 Sample 6 Sample 7 Sample 8

Sample 9 Sample 10 Sample 11 Sample 12shake until 32'00" 34'00" 40'00" 42'00"

reading 32'40" 34'40" 40'40" 42'40"reading 36'00" 38'00" 44'00" 46'00"reading 4:32'00" 4:34'00" 4:40'00" 4:42'00"

Sample 13 Sample 14 Sample 15 Sample 16shake until 48'00" 5000" 56'00" 58'00"

reading 48'40" 50'40" 56'40" 58'40'reading 52'00" 54'00" 1:00'00" 102.00"reading 4:48'00" 4:50'00" 4:56'00"

Sample 17 Sample 18 Sample 19 ' _ 20shak until 1:04'00" 1:06'01)" 1:08'0C1 1:10'00'

reading 1:04'40" 1:O6. U" 1:08'40" 1;10'40"reading 1:08'00" 1:10. ' 1.12'00" 1;14'00"

3, rading 5:04'00" 5:0600" 5:08'00" 5:10'00"

Sample 21 Sample 22 Sample 23 Sample 24shake until 1:16'00" 1:18'00" 1:24'00" 1:26'00"

reading 1:16'40" 1:18'40" 1:24'40' 1:26'40"readdng 1:20'40" 1:22'00" 1:28'00" 1:30'00"reading 5:16'00" 5:18'00" 5:24'00" 5:26'00'

39

Sample Sample 2 Sample 3 Sample 4

shake until: 0" 02'00" 08'00" 10'00"1. reading 40" 02'40" 08'40" 10'40"2. reading 04'00" 06'00" 12'00" 14'00"3. reading 4:00'00" 4:02'00" 4:08'00" 4:10'00"

shake until 16'00" 18'00" 24'00" 26'00"1. reading 16'40" 18'40" 24'40" 26'40"2. reading 20'00" 22'00" 28'00" 30'00"3. reading 4:16'00" 4:18'00" 4:24'00" 4:26'00"

USEFUL ADRESSES

Part of the equipment used in the laboratory is purchased from overseas. Incase of restocking spare parts, breakdowns or relacement here someadresses:

Dispensers/diluters, multisample stirrer, superfloc, etc.:

Custom Laboratory Equipment Inc.P.O. Box 757205 E. Michigan Avenue

Orange City, Florida 32763USA

Telephone: 904-775-2322Telex: none

Contact: Dr. Alen B. Hunter

Superfloc:

American Cyanamid CompanyP.O. Box 32787

Charlotte, North Carolina 28232USA

Automatic extractor:

Centurion International Inc.P.O. Box 828464555 North 48" Street

Lincoln, Nebraska 68501USA

Telephone: 402-467-4491Telex: 48-4377 CENTURION LCN

Contact: Debra Hilde

Barnstead water purification system, steam washer, ultrasound bath:

Curtin Matheson Scientific International9999 Stuebner Airline

Houston, Texas 77038USA

Telephone: 713-820-9898Telex: 46-20313

Contact: Williams

40

Kjeltec dis iller:

Tecator ABP.O. Box 70

S-263 01 HoeganaesSweden

Telephone: 042-42330Telex: 72 695

Automatic titrator, pH-electrodes, coductivity cell:

Schott Geraete GmbH orP.O. Box 1130Im Langgewann 5

D-6238 Hofheim a.TsFed. Rep. Germany

Telephone: 06192-8081Telex: 410471

Atomic Absorption Spectrometer:

Varian Techtron Pty. Ltd. SMM InstrumentsP.O. Box 38622

Springvale or Booysens 2016Australia South Africa

Telephone: Telephone: 434-1010Telex: Telex: 4-85881

Balances:

Sartorius GmbH or Zeiss West GermanyP.O. Box 3243 P.O. Box 1561

D-3400 Goettingen 2000 JohannesburgFed. Rep. Germany South Africa

Telephone: 0551-308 289 Telephone: 402-2860Telex: 96 723 Telex: 4-88346

Contact: Frank Bender

Klever instrumentsP.O. Box 483

Jukskei Park 2158South Africa

Telephone: 011-704-3017/8Telex:

Shakers, sieve shaker, test sieves:

Labotec Pty. Ltd.P.O. Box 43161

Industria 2042South Africa

Telephone: 673-4140Telex: 4-51117

Contact: Sharon Brett

General Laboratory ware and reliable help for various problems:

QuadralabP.O. Box

BergyleiSouth Africa

Telephone:Telex:

Contact: Patrio Horey

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PIBag 003, Gaborone, Botswana

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