Transcription
AG 801 85 011FIELD DOCUMEN I 3Soil Mapping and Advisory ServicesBotswanaSOIL TESTING PROCEDURESFOR SOIL SURVEYPart 2Laboratory Procedure ManualUNITED NATIONSFOOD & AGRICULTURE44ORGANIZATION OF THE0 DEVELOPMENTUNITED NATIONS7431PROGRAMMEGABORONE, 1988REPUBLIC CFBOTSWANA
AG: BOT/85/011Field Document 3Soil Mapping and Advisory ServicesBotswanaSOIL TESTING PROCEDURESFOR SOIL SURVEYPart 2:Laboratory Procedures ManualbyReinhard BreitbartFAO ExpertFood and Agricultural Organization Of The United NationsUnited Nations Development ProgrammeGaborone, 1988
TABLE OF CONTENINSAMPLE RECEPTI()N, GRINDING AND STORAGE. . . . . . .Equipment. . . . . . . . .Procedure.pH-DETERMINATIONReagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . .Preparation of saturated soil pasteSaturated paste extract . . . . . . . .ELECTRICAL CONDUCTIVITYProcedure . . . . . . . .Temperature correction. . . . .SOLUBLE SALTS DETERMINATION. . . . . . .Procedure .Calculations. . . . . . . . . . . . . . . . .PHOSPHORUS DETERMINATIONEquipment. .Reagents. . . . . . . . . . . .4. . . . . . .444. . . . . . . . . . . . . . . . . . . . . . . .,.5Procedure .Calculations. . . . . . , . . . . . .OR(;ANIC CARBON DETE1RMINATIONEquipment. .Reagents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17.18. . . . .1818. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2020. .20. . . .22. . . . . . . . . . .18181919. . . . . . .1515151516.131314. . .1111111111121212161616. . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 normal, neutral ammonium acetate solution1 normal, acidified potassium chloride solution4% boric acid solution . . . . . . . . . . . . . . . . . . . .Mixed indicator50% sodium hydroxide solution . . . . . . . . .Sulfuric or hydrochloric acid 0.01 n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . .Procedure .Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Procedure . . . . . . . . . . . . . .Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Equipment. .Reagents. . . . . . . .CEC-DETERMINATION. . . . . . . . . . . . . . . . . . . .Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67. . . . . . . . . . . . . . . . . . . . .999. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6. . . . . .6. . . . . . . . . . . .Digestion solution . . . . . . . .Standard solutions . . . . . . .Supertloc 127 Flocculant solution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22. . . . . . . . . . . . . . . . .Extracting solution for Bray and Kurtz IExtracting solution for Bray and Kurtz IIColor reagent A . . . . . . . . . . . . . . . .Color reagent B . . . . . . . . . . . . . .Standard solutions for calibration curve .Settings. .2. . . . . . . . . . . . . . . . . . . . . . . . .Equipment, reagents and standards. . . . . . .1. . . .Calculations and data storage . . . . . . . . . .Equipment. . . .Reagent. . . . . . . . . . . .SATURATED PASTE EXTRACT . . . . . .
. . . .Reagents. . .lnterelement effects during Ca and Mg determinationEXCHANGEABLE CATIONS DElERMINATION. . . . . .Preparation of Ca/Mg standard solutions (meq/litre)Preparation of K/Na standard solutions (meq/litre) .Alternative K/Na standard solution in ppm . . . . . . . . . . .28. . . . .,. . . . . . . . .PARTICLE SIZE DETERMINATIONEquipmentReagents. . . . .Preparation of SolutionsPretreatment of SamplesProcedure . . . . . . . . .,. . . . . . . . . .Calculations . . . . . . . . .II. . . . . . . . . . . , .23232324252728.Ca/Mg and K/Na with Atomic Absorption Spectrometer . . . . . .Preparation of the Varian AAl275 Atomic Absorption SpectrometerCalculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .K/Na determination with 'CORNING 400' flamephotometer . . . . . .31333333334343637
SAMPLE RECEPTION, GRINDIN(; AND STORA ;ESample 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.
pH-DETERM1NATIONReagents:For pH-1120:For pH-CaC12:distilled water0.01tn CaCI, solution( 0.01m CaC12 1.11 g CaC12 per1litre 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 H20dist. with the dispenserconnected tu the water drum.l'o the samples in the bottles marked 'pH-CaCI,' add 50 inlCaCI,-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 ittakes muchlonger 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),reading withrespectively in the pH 9.2 buffer solution (for alkaline soils). Set the meterthe 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'TReagent:distilled water1(juif)ntenit:24-place.hanical vacuum extractor cups for extractor.large beakers (800-1000m1)burctie (1(1(1 ml)spatuLtPrsparation of saturated soil paste:Weigh 200 g of soil into beakersWith 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).4tfft'mìxing allow Hie soil to stand for one hour or more. Then check saturaIf 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 addithrwiif 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.4criierizi
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 CONDUCTIVITYProcedure:"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 set) switch to a higher range.range, indicated by display of (1.There are rive range settings0-2000 micro S/m0-20.0() mS/m0-200.0 mS/m0-2000 mS/m0-20.00S/mAs 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
FigureITemperature correctilin table (US. Salinity LaboratorStaff. 1954)
SOLUBLE SALTS DETERMINATIONEquipment, reagents and standards:tiaiue equipttietit anti same cheinicals as for exchangeable ationsornbined stock solutions:200 ineq/1 t'a50ineq/IK 50 ineq/150 ineq/I NaPrepare diluted stock solutions and standard series in the same vay asf.determination, only thatthe volumetric flasks are filled up with distilled water and not with ainioni;atCLli4111114,'t,PrOtled re:l'ipette I nil saturated paste extract in toand shake well tu mix.0oil volumetric flask\ Olt: it absorbance readings of simples are too I,.up will: dc,ii111.:tt.1445can hechosen.The 'I, dilution' then is calculated:Size of volumetric flask:nil saturated paste extractFurther procedure is exactly as for exchangeableCalculations:If linear regression curve is calculated concentration C of soluble cations in ntc:tsioring sointion is:C -a*E ba, b regression coefficientsE Extinction (absorbance reading')If no linear regression curve is calculated concentration C ot soluble cations in measuring solutionis:E/eExtinction (absorbance reading)e Extinction coefficientEe is calculated from standard curve:e (El/ClEl, E2, E3,Cl, C2, C3,E2/C2 E3/C3 En Absorbance readings of standardsCI( Concentrations of standards Number uf standards4) En/Cn)
Concentration I: of soluble salts in soil Imeq/11KCext rac:.Soil ] is::11);2.dilution /CSeigio(Million2(ItItkiimiiit': II ,t2ti FOEuscii to/hut cTraits( il- i1)0.1A,110rctsk)10
PHOSPHORUS DETERMINTION(Bray and Kurtz 18e11,1 1 wo 25 litre drums for extracting solotim:\lulti-tunnel rack for 33 funnels ot,6.aineter.appywkVi'ter paper 1Vhatman 44 or 42, 9 cmBrinkman eolorimeter PC 600ooloinneter, preleisthl. ( niNO 1.'dipin' pi-obi'o an othcrStoll threngit cet!N111(1ti: one d1iql1 it iii'ivolono thrkk olionot'urninc( -11)One SCD 1Nvitkorlion dilute!.".One multisamTm. stirrerklM11011ErFlUoride,A11,N1141Hydrochloric add kola101kotimon)-Potassium-tartrateSulfuric acid conc.Ascorbic acidPotassium-dihydrogen phosphateK(ShOit 41140,,l1 510NII,Mo,t),, 111,i)(98(,i1(1-1,PO4solution for Bray and Kurtz I:0.03 in NH41. irsfICIdd 53.6 nil 11C1Dissolve 27.78 g NI-14F in approximately 500 ml distilled/deionized ateu(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 HC1To time dissolved 27.78 g NH,F add 214.5 ad WTI cone. (36%).Proceed as above.11
telor reagent A:I.Dissole in a beaker 30Aintrionintn-hepta-molybdat. in about 250 int 1190 dist.Dksoke in a SeC01160.727 g Antinomy- Potassium- tartrate.th'zti,CrFill 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,mid 3 liters distilledFinewell9real.:( it4Ot33 samples plui,01)1)1'0\1111;1ft ur,olotion.eus ,tikstiaidal-os is 250tor 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/1Pipette 50 ml of 100 ppm solution into 500 ml volumetric llask.Proceed as above.1."
3. Standard series:Pipette10, 20, 30, 40, 50 mlof 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/ISettint:A soil/extractant ratio of 1:7 is used.Set Me dispenser for the extractant to 35ml. Using a AD 3 'three volumi -.three aliquut.it must be made sure that all three syringes dispense precisel) the sameSet the SUD 1 'combination diluter-dispenser' to dispense Sinl cok,7take u 01,11 extract.'nit resulting dilution of 1:2 for samples and standardsAsorlIanee for the highest standard is around 0.2-0.25.is founddispenseltune.15dul (list, water andconvenientProcedure: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:magnetic stirrer until dissolved.acid and stir with aAdd 2.5-3 g AscorbicNOTE: 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 repeatedwith 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.13
S.third bottle rack tras next tu the one with the tiltrates, Put tire double plastic tips ufPlaotitc 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.t beaker with distilled water to clean the outside.l/ip the tips rIivay. Eill a little wore tiran 20 ml Of tire stttiidards andpenserV of bottles and transfer with the diluterFor the standards proceedextracting solution t r theitrio a econd ro','.\TNT1101(1, (0hour the blue color of the mthe spe-trophotometer determine the absorptionw.;.% etengttL1. Want . fl11. Zen).1fhis stan 1;111111.111R:1114(i u0h:txceptionse slatit1140!,bdate cmnplex is fu 11v developedstandards and sato ples at 661ille relatively phosphorns-poor soils most1) I diluter:he P-concentration is 4eileralshould be changed.1101t."Calculations.11C111:11101:,data is done Ivith tire Hewlettprinting.,101¡;11.1mierc11. thkr1,11in ppin P is cal ut.ttediied the concentraConcentration C of P in solution is:I t on coetlicientstandardThe [slim nun coefficient is kalculatedroncentratioi r uf the standards is known ExtinctiE3El F2.is read from tire spectrCuf standard 1, 2, 3,., ncentration of standard 1, 2, 3,., nmber of standardsEn Extinctionulated:nExtract r WeighNOTE: \\Atli dilution is not the initial dilution with the diluter-dispenser meant because [Itere thestandards are diluted too.14
,1,70): ,Z'Digestion so utSodinin tlichroinalt5
StandarttiII 100 tul VOIUo1.1iwculant .olutionsuperiloiil,IC , neon-,11 andIthighlyIS1 gram per 10 liters of solutiss.11I 11'4 prl'ILIT1stirI VI11)0)1 mi beaker. Stii110t.11111Ct1/1 111111oii ;teriuulot 55111cr('are nit(:lug Wilt II, disto,iwccioUIi,ith a magnetic1)11 ,,1sin el01 Ow !,tilv, titiiit .lot tutti 110, t1iit lttaken II)1)11.'NUnt111101:ilatiinì P'511110 VC(1-11n SI)1dis (n.eidiluter to1('fflanttu 2inlolOilitItt lit-f.Pipettet,11oni tuiptilur (hlOlen, linkditt,4,di iddonlociisIIoi,.(11k11 6111,lint ttofit\tttuì)!ninon-tiertliic 127 /loci 111:int silin ion111t.flourf;.(t ttllrimi
Vith thaliquot from liw 'lcar supernatant solution arid transtcr Otte,tir tire sediment.) .Iso tratislet shiiid,iiiI;trefoil% notteta bottle of tue bottl&,ui(1 Wane.\leasure absorba rice ith a lirinkman colorimeter or allwith flow through cel at 570 tun.i,rtculations:Soil Survccattiputcr,-\ hen I g(-Mahon acc.-veighed the standard tc-c -o,.,-esponds w tin0.50, 2.50g gluco-:Glut1% org.I 0.0Ig (in100Ig1g1.00 rcumNOTE:IItheg.Cexceeds corresbe repeated wOh Oids then1.0, 2.0, 3.0, 4.0, 6.0 % org. C,or aiiirÌeswith more than 6% tog (' differentmust be applied,itple dry,'hod)
Ir\utottlalic'tractor, 24 pl:u.-1)1.TERMINATIucept ikoir1111,"s1onoject'I, hi into "Sample syringes(Mom!, (litIII1oalytic:II tilr phcal sims(milicctutg sliingialt1aiol Schoen, No.7.8(kiishedou1 orLe.kr.\unit w1.jcitee,\uit&ituitttc iIIitillikIunit)igestion tiMes. 2511 nilConical Flasks. 2511 niloltimetro: flasks10i11111Reagents:Volotoolow\ceto acidXmoomi:t ,olOtioohoric ;1C1d' odiOto 11,ydroicie flake,ohitlietric solution kit sidliiroEthanol 95() (methylated spiricEthanol 50 k (methylated spir0;Pluassitun chlorideHvilrochloric acid ()%ydrochlock'.1 normal, neutral ammonium acetate solution:Dissolve 1926.8 g ammonium tietutu io 5 liters (listilled water.\Lilo.- up tu 25 liteisWilc,1 pH to 7.0 with eitherlCeit, acid kilsolutionIIIiIIIIUiaif p1 norrnak acidified potassium chloride solution:Dissilhe !Sol," g potassium chloride iimakiRaiAdd 125 nil 36% Hydrochloric acid.Nlals:)1) to 25 Lad 51distilled %atec, -
ddfleat it, near boiling and stir until dissolved.I rawder2-through a large polyethylene funnel i,tliters of distilled ssater.Add a few nil ofiiidictor' and Illakt'Mixed indicator:Dissolve0.5 gand0,1 g h1ìrtliin WO tul 95% alcoholres.)! greent.('5t.' liters.\ rt. it% RItuttiti
5W; stuliwt; tivitroxide solotion:ifoo:Aarviidiv;a a 5 litre beaker,deionizedij to it volume of 5000 nit.hssoieti andst1r:o2c taUfrfti Kjcitc:IMO' ill I )110.1I1110;,. has 10 litersand goggles are imperative!Sulfuric nr hydrochloric acid 0.01 nMute moltnadric solution accordinufN'0111111VISOlUtI01, IS I normal pipette 10 nil intovolumetric flask and till v.ithwater to about cm below time marl. Put flask iii Nvaterbath temperate al 20 C for 3f,minutes.Then tilllo Mark.(1IProcedure:1.Prepare sample extraction tubes by placing approxiiiin a syrirt:;:. harrel.g 0 litter p u I p formed in to a haForce 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.20
\ttaihio sample tubes ,-11)e sidestown.1 lac e r1LO,abes in sample tidies. Fill t aluilit 4-z01 ethanol shoul(i bc justt ittle less .;liati ti 11.'1/41Icrt15.c\ULIOUit off.,1, ethanol. fillmarl.111 markpull plung!.77(10%u,And1211)11'AMMO VaSill.ib s)rifles with acidified in potassium chloride solution and estrai.l. Collect eslract insultintetric flasks. Fill up to inark vv oh potassium chloride soliition mid shake N/A tO1I'll/01V16,stofiped !urn.I50 ml aliquod KCI extractdigestion tul)es.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,. witclidistillitig 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, acidsodium livilroxide solution by puling; the lever of the 'alkali moor'()pen steam valve and distill 4-5 minutes coiieet 125-150 nilinpositi,,i,\aid 51)%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, or1 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»21
ztr4ct/a1iquot( tLai :1Ifl 11!,C(.1 for titrationI)nit blaitc titrationoormaiify of acid (Atrait Intl(1.)rinitNviglit'uiI - (1-1))*(.1.01'''100125cic ime/100g soil] (t-b)0.8101151.
EXCHANGEABLE CA IONS DETERM NAT NEquipment:olunietric flasksSD-1 diluterSO nil polyethylene cont,iiiier,Absorptioa,irlical);Nii is,11 01111111M id oridu- 66.6:LaittimIllimcilloride,.aleinmeartionateL. at'('),S, '7\ iloi ideNa'Cl.,('or11%, Ni --- ti:' 6:kVil-1, .)-- ! 38.1 iWs. ) .2-16,-IS\IA% .7 5:i.-14Kticts during Ca and Mg detererneutation.to aluminuni and silicon and iotlizito,i,t.11r,1";INV 371.1"'WO) 100.0971,on 1i o the IliumiiUt 0o y 1 ,doittionni ii) th,tictet'uttiiiation, Ionization otMini» ric,Aile l i ii,mitatspei.i.),.iY I intbred in. ell by addiuig strontinioproppna Sr or La concentitct s1ncl NotationSrC12*(41.,0 in 5 liters dist, water, Fois,.itSr)ordissonc I 338,7 g LitC13*711"0 in 5 liters dist. water. (For better solubilityEaC1,'7(10 37.-rf) La)2000 pion working solutionstock solutiondistilled water,5I1
Preparation or (standard solutionsComb:soli ,toek, solution 200meti/1 Ca 50ineti/1 1k1gDry CaC() ;yid N1,.,.' (14!*7112i.) di 100 Celsius in drying oven,Cir('()f 0.0906 It):anii40.0 a1.:111;17HVOIllinetrie-t. ball' %vial ,.LH,Ma: carbonate.(' in121,ri1f)er8ttire ;,.'Owmark! and sliiionicsvelLDiluted CMg stock solutionlutiw: into 500 11 vokimetric flask,!'ipt.ti;1111 lo about 2 cm bch,w unia. lAithileterrinuit ion),Orion (tempt.::-;ilor%;up tuTit:, so1:5);1;1n .annionisiwin \!1tsk and shake. vell.stoppe;coutiiny,40 meg Ca/1 and 10 meg Mg/1.!.kndard seriesSc; ml10, 20,5,'OJllti1)fl nito 100 nil volumetric flas;,,Fill to about 1 cm below the mark with1u ammonium acetate solution,Adjust. temperature tu 20 C in waterbath,After 30 minutes till up tu mark, stopper flasks and shake we24
--t;3;3;1.irti2ineti:4 met!4.-0:111(1.itti. Lttitlarti3,fauIirdtic3intii I113eqIli wet}2113/!iti /2.5101,. 1,1ti intAi!Itlyratyon of K/Na standard Nolui,31.3(1/1 Kt 10,"1110ent heit)%k ¡mirk SSitlltIt sitter.,VW lip to ;Wont'e21C--)pperStore01111iVOItOtIIIiiOttll Olt Intl) 5t10iiitiiiitiii,ii,i11.141t((-EtWWI(C inFir;mil- 3013-3t solution Loot . ,2 rnt25!Fit loaf lop
\iternative K/Na standard solution in ppiii:Combind stock solution 2000 mini kplan Na3.8133 g KC!Weighand0.6355u.NaCIhit() 10001 \ 11)11(%I)iluted stock St1111i1011Piocilc ill laThe solution contains;npin K anti2:::;p1Standard seriesPipette;5, 10, 15, 20 50 nilstock solution intr. 200 ini011,1111CtriCProceed asThe Nonni/ins contain:1, StandardStandardStandardStandard5, Standard5 prim K10 mini K15 ppin K20 mini K i50K0.625 ppin1.25mini Na1.875 ppin2.56.25ppin N;;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 10Connect 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 inlwater.)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,ilpu 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. Svinto vials Milne, the automatic sample changer.-ontainers tr mix Then 1111 olutionPreparation uf lhit Varian ,lA/27.:. Atomic Absorption
Laboratory Procedure Manual 44 UNITED NATIONS ORGANIZATION OF THE FOOD & AGRICULTURE 0 DEVELOPMENT UNITED NATIONS 7431 PROGRAMME 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 PROCEDURES
