soil fertility evaluation ppt.

SOIL SCIENCE PPT

1. Chapter 3
Soil Fertility Evaluation

2. Theproperrateofplantnutrientis
determinedbyknowingthenutrient
requirementofthecropandthenutrient
supplyingpowerofsoil.
Hence,theevaluationofsoilfertilitybecomes
important.
Soilfertilityevaluationisessentialfor
balancednutritionofthecrops.

3. Soilfertilityevaluation:
Knowthenutrientsupplyingpowerofsoiltothecrop.
Advantageoffertilityevaluation:
•Ithelpsinmaintenanceandimprovingsoil
productivity.
•Soilfertilityevaluationisthekeyforadequateand
balancedfertilizationincropproduction.
•Balancenutrientsupply/Balancedfertilization:
Itreferstotheapplicationofessentialplantnutrients
inrightamountsandproportionsusingcorrectmethods
andtimeofapplicationsuitedforspecificsoil-crop-
climaticsituations.

4. Techniques are commonly employed to
asses the soil fertility are
1.Soiltesting
2.Analysisoftissuesfromplantgrowingon
thesoil
3.Biologicaltestsinwhichthegrowthof
higherplantsorcertainmicro-organisms
isusedasameasureofsoilfertility
4.Nutrientdeficiencysymptomsofplant

5. 1.Soiltesting:
•Soiltestingisthechemicalanalysisthatprovidesaguideline
foradditionofamendmentsorfertilizertosoils.
•Theprimaryadvantageofsoiltestingisdeterminingthe
nutrientsstatusofthesoilbeforethecropisplantedas
comparedtotheplantanalysis.
ObjectivesofSoiltesting:
•Soilfertilityevaluationformakingfertilizerrecommendation
•Predictionoflikelycropresponsetoappliednutrient
•Classificationofsoilintodifferentfertilitygroupsforpreparing
soilfertilitymapsofagivenarea
•Assessmentofthetypeanddegreeofsoilrelatedproblemslike
salinity,sodicity,acidityetc.,andsuggestingappropriate
reclamation/ameliorationmeasures

6. Stepsinvolvedinsoilanalysis
i.Sampling
ii.preparationofsamples
iii.Analyticalprocedure
iv.Calibrationandinterpretationoftheresults
v.Fertilizerrecommendation
1.Sampling:
•Soilsamplingisperhapsthemostvitalstepforany
analysis.Becauseaverysmallfractionofthehuge
soilmassofafieldisusedforanalysisandconverted
inhectarebasis.Soitbecomesextremelyimportant
togetatrulyrepresentativesoilsamplefromthefield.
2.Preparationofsample:
•Drying,grindingandsievingaccordingtotheneedof
analyticalprocedure

7. 3.Analyticalprocedure:
Asuitablemethodisonewhichsatisfiesthefollowing
threecriteria.
(i)Itshouldbefairlyrapidsothatthetestresultscanbe
obtainedinareasonablyshortperiod.
(ii)Itshouldgiveaccurateandreproducibleresultsofa
givenSampleswithleastinterferencesduring
estimation.
(iii)Itshouldhavehighpredictabilityi.e.,asignificant
relationshipoftestvalueswiththecropperformance.

8. Following chemical methods are widely used for
determination of different nutrients
NutrientsMethods Merits and demerits
Total NKjeldahl
method
This method is time consuming, lengthy and
costly
Rate of mineralization of N varies with the
soil
Organic CWalkley
and
Black
method
This method is simple and rapid
Based on C:N ratio which is varied (7.7 to
11.7)
Available
N
Alkaline-
KMnO
4
Extract part of organic and mineral N

9. Conti….
Available
P
2O
5
Olsen's method
for alkaline
soils
High efficiency of HCO
3ion to remove
P from Ca, Al and Fe
Reduce the activity of Ca
Used in slightly acidic, neutral and
alkaline soil
Bray's method
for acid soils
High efficiency of F ion in dissolving P
Useful in acidic or slightly calcareous
soils
Available
K
2O
NH
4OAc
extratable
Higher efficiency of extraction as
compared to salt solution
Inefficiency to remove part of non
exchangeable K, which is considered to
be available to some extent

10. Conti….
Available
S
0.15%
CaCl
2
extractable
Extract water soluble S and
adsorbed S
Heat soluble
S
Heat soluble-extract WS +
organic S
Time consuming and lengthy
procedure
Available
Micronut
rients
DTPA
extractable
Extract complexed, chelated and
adsorbed form of Fe, Mn, Zn, Cu

11. 4.Calibrationandinterpretationoftheresults:
Forthecalibrationofthesoiltestdata,soilsaregroupedinto
high,mediumandlowcategory.
Forcategorizationofsoil,theparticularnutrientareselected
andthetestcropisgrownwithvaryingdosesofparticular
nutrientandbasaldoseofothernutrients.
Plotsoiltestvaluesagainstthepercentageyieldtocalculate
therelationshipbetweensoiltestvaluesandpercentyield
response
Percent
yield =
Cropyieldwith
adequatenutrient
-
Yieldofcontrolwithout
additionofparticularnutrient
understudy
x100
Crop yield with adequate nutrient

12. Critical level of nutrients in soil:
SN Nutrients Category
Low Medium High
1.Alkaline KMnO
4-N (kg/ha) <250 250-500>500
2.Olsens-P
2O
5(kg/ha), <28 28-56 >56
3.Neutral N NH
4OAc-K
2O <140 140-280>280
4.0.15% CaCl
2–S (mg/kg) <10 10-20 >20
5.DTPA extractable Fe (mg/kg)<5 5-10 >10
6.DTPA extractable Mn(mg/kg)<5 5-10 >10
7.DTPA extractable Zn (mg/kg)<0.5 0.5-1.0>1.0
8.DTPA extractable Cu (mg/kg)<0.2 0.2-0.4>0.4
9.Hot water soluble B (mg/kg)<0.1 0.1-0.5>0.5
10.NH
4OAc soluble Mo (mg/kg)<0.050.05-0.1>0.1

13. Thisclassificationindicatedthat
lowclassofsoilwouldrespondtoadded
fertilizermeansadd25%morefertilizer
thanrecommendeddose.
Mediumclasssoilmayormaynot
respondtoaddedfertilizer,add
recommendeddoseoffertilizer.
Highstatussoilsdonotrespondtoadded
fertilizer,add25%lessrecommended
dose.

14. 2.PlantTesting:
1.Analysisoftissuesfromplantgrowingonthesoil
Planttissueanalysisisthedeterminationoftheconcentrationof
anelementinaplantsampletakenfromaparticularportionofacrop
atacertaintimeorstageofmorphologicaldevelopment.
Theplantanalysishasbeenusedasadiagnostictoolor
complementarytosoiltestingbecause
(i)Inmanysituations,thetotaloreventheavailablecontentofan
elementinsoilfailstocorrelatewiththeplanttissueconcentration
orthegrowthandyieldofcropduetomanyreasonsincludingthe
physicochemicalpropertiesofthesoilsandtherootgrowth
patterns.
(ii)Ontheotherhand,theconcentrationofanelementintheplant
tissueispositivelycorrelatedwiththeplanthealth.Therefore,the
plantanalysishasbeenusedasadiagnostictooltodeterminethe
nutritionalcauseofplantdisorders/diseases.

15. Following steps (procedure) are included in
plant analysis
i.Thecollectionoftherepresentativeplantparts
atthespecificgrowthstage,
ii.Washing,dryingandgrindingofplanttissue,
iii.Oxidationofthepowderedplantsamplesto
solubilizetheelements,
iv.Estimationofdifferentelements,
v.Interpretationofthestatusofnutrientswith
respecttodeficiency/Sufficiency/toxicityon
thebasisofknowncriticalconcentrations,

16. Plantanalysisapplications:
•Diagnosisofnutrientdeficiencies,toxicitiesor
imbalances
•Measurementofthequantityofnutrients
removedbyacropstoreplacetheminorderto
maintainsoilfertility
•Estimatingoverallnutritionalstatusoftheregion
orsoiltypes
•Monitoringtheeffectivenessofthefertilizer
practicesadopted
•Estimationofnutrientlevelsinthediets
availabletothelivestock

17. CollectionandPreparationofplantsamples
1.Collecttherepresentativeplantpartsatthespecificgrowth
stagebecausenutrientcontentinplantvarywithgrowth
stageanditreflectthenutrientconcentrationsatparticular
growthstage.
2.Collecttherecentlymaturedfullyexpandedleavesjustbefore
theonsetofthereproductivestageandputinperforated
paperbags.
3.Theplantsamplesareoftencontaminatedwithdust,dirt
andresiduesofthesprays,etc.soitneedtobewashed
firstunderarunningtapwaterfollowedbyrinsingwithdilute
HCl(0.001N),distilledwaterandfinallyindeionizedwater.
4.Thewashedsamplesaredriedinahotairovenat60±5°C
foraperiodof48hoursandgroundinastainlesssteelmillto
passthroughasieveof40/60mesh.

18. Oxidationofplantmaterial
•Themainobjectiveofoxidationistodestroythe
organiccomponentsintheplantmaterialtorelease
theelementsfromtheircombinations.
•Theplantmaterialscanbeoxidizedbytwo
methods
(i)Dryashingatacontrolledhightemperature
(500ºC)inamufflefurnace
(ii)Wetdigestioninanacidoramixtureoftwoor
moreacids.

19. i)Dry-ashing:
(a)Thepowderedplantmaterialsaretakeninsilicacruciblesandashedina
mufflesfurnaceat500ºCfor3-4hours.
(b)Temperatureisanimportantconsiderationindryashingbecause
Nitrogenandsulphur,beinghighlyvolatile,lostduringdryashingevenat
500ºCandathighertemperatures(above500ºC)elementslikeKmay
alsobelost.
(c)Theashisdissolvedin2mlof6NHCl,heatedonahotplatetonear
drynessandagaindissolvedin10ml0.01NHClor20%aquaregia
beforemakingupthefinalvolumewithdistilledwater.
(d)Theseextractsmaycontaindifferentamountsofinsolublematerials,
mainlysilica,dependingupontheplantspecies.
(e)Keeptheseextractsforsometimetosettledowninsolublematerialsand
separatebyfiltrationbeforeestimationofdifferentelements.
(f)Allelements,exceptNandS,canbeestimatedfromtheseextractsby
suitabletechniques.
(g)Theresultsobtainedbythismethodarequitesatisfactoryand
comparabletothoseobtainedbywetdigestionprocedures.
(h)Moreover,Bcanonlybedeterminedbydryashingsinceitisvolatilized
duringwetdigestionwithdi-ortriacidmixtures.

20. ii)WetDigestion:
Wetoxidationdigestionreagentsandtheirapplicability
Sr. Reagents Applicability Remarks
1H
2SO
4/HNO
3Vegetableorigin Mostcommonlyused
2H
2SO
4/H
2O
2Vegetableorigin Notverycommon
3HNO
3 BiologicaloriginEasilypurifiedreagent,
shortdigestiontime,
temperature350
0
C
4H
2SO
4/HClO
4BiologicaloriginSuitableonlyforsmall
samples,dangerof
explosion
5HNO
3/HClO
4Protein,carbohydrate
(nofat)
Lessexplosive
6HNO
3/
HClO
4/H
2SO
4
Universal(alsofat)Nodangerwithexact
temperaturecontrol

21. Conti……
GenerallyHNO
3
,HClO
4
andH
2
SO
4
acidsareusedin
wetdigestionmethod.
Theseacidsareusedeithersinglyorin
combinationsoftwoorthreeacids,e.g.HNO
3
and
HClO
4
(10:4ratio),HClO
4
andH
2
SO
4
(4:1ration)
andHNO
3
andH
2
SO
4
(10:1ratio)oratripleacidisa
mixtureofHNO
3
HClO
4
andH
2
SO
4
(in10:4:1ratio)
Thepowderedplantsamplesaredissolvedinthese
suitabledi-acidsortri-acidsmixtureusinghotplate
atnearly350ºCtillclearthecontent.
Coolthecontentandaddsomedistilledwater,filter
andmakedesiredvolume.
Thisfiltrationcanbeusedforestimationofdifferent
elements

22. Rapidtissuetests:
•Tissuetestsarerapidandareessentially
qualitative.
•Thenutrientsareabsorbedbyrootsand
transportedtothoseplantpartswheretheyare
needed.
•Theconcentrationofcellsapisusuallygood
indicationofhowwelltheplantissuppliedatthe
timeoftesting.
•Theplantparts,usuallyleavesareremovedand
plantsapisextracted.
•Theplantsapisusuallytestedfornitrate,
phosphorusandpotassiumbycolorimetrictests.

23. DRISapproach
•RecentlyDiagnosisRecommendation Integration
System (DRIS)issuggestedforfertilizer
recommendation.
•Inthisapproach,generallyplantsamplesarecollected
fromfarmer'sfields.
•Theseplantsamplesareanalyzedfornutrientcontent
andtheyareexpressedasratiosofnutrientswith
others.
•Thenutrientswhoseratiosarenotoptimumforhigh
yieldsaresupplementedbytopdressing.
•Thisapproachisgenerallysuitableforlongduration
crops,butnowadaysitisbeingtestedforshort
durationcropslikesoybean,wheatetc.also.

24. 3.Biologicaltests:
•Inbiologicaltest,thegrowthofhigherplantsor
certainmicro-organismsareusedasameasure
ofsoilfertility.
•Thebiologicalmethodsconsistofraisingacrop
oramicrobialcultureinafieldorinasoilsample
andestimatingitsfertilityfromthevolume
(yield/mass)ofcropormicrobialcount.
•Thesemethodscanusedfordirectestimatesof
soilfertility,
•Thesemethodsaretimeconsumingand
therefore,notwelladaptedtothepracticeofsoil
testing.

25. 1.Fieldtests:
(i)Thefieldplottechniqueessentiallymeasures
thecropresponsetonutrients.
(ii)Inthesetests,specifictreatmentsareselected
andrandomlyassignedtoanareaofland
whichisrepresentativeoftheconditions.
(iii)Severalreplicationsareusedtoobtainmore
reliableresultsandtoaccountforvariationin
soil.
(iv)Fieldexperimentsareessentialinestablishing
theequationusedtoprovidefertilizer
recommendation,Maximumprofitability,and
minimizeenvironmentimpactofnutrientuse

26. 2.Potculturetests:
Thepotculturetestutilizessmallquantitiesof
soiltoquantifythenutrientsupplyingpowerof
asoil.
Selectedtreatmentsareappliedtothesoils
andacropisplantedandevaluated.
Cropresponsetothetreatmentscanbethan
determinedbymeasuringtotalplantyieldand
nutrientcontent

27. 3.Laboratorytests
(a)NeubauerseedlingMethod:
•TheNeubauerseedlingtechniqueisbasedontheuptakeofnutrient
bygrowingalargenumberofplantsonasmallamountofsoil.
•Theseedlings(plants)exhausttheavailablenutrientsupplywithin
shorttime.
•Thetotalnutrientsremovedarequantifiedandtablesareestablished
togivetheminimumvaluesofnutrientsavailableforsatisfactoryyield
ofvariouscrops.
(b)Microbialmethods:
•Intheabsenceofnutrients,certainmicroorganismsexhibitbehaviour
similartothatofhigherplants.
•Forexample,growthofAzotobacterorAspergillusnigerreflects
nutrientdeficiencyinthesoil.
•Thesoilisratedfromverydeficienttonotdeficientintherespective
elements,dependingontheamountofcolonygrowth.
•Incomparisonwithothermethodsthatutilizehigherplants,
microbiologicalmethodsarerapid,simpleandrequirelittlespace.
•TheselaboratorytestsarenotincommonuseinIndia.

28. 4.Nutrientdeficiencysymptomsofplant
1.Theplantrequiresseventeenessentialnutrientsfortheir
optimumgrowthanddevelopment.
2.Itisgoodtooltodetectdeficienciesofnutrientinthefield
3.Whenaplantnutrientisbelowcriticalconcentrationinplant,
itshowsdeficiencysymptoms.
4.Thesesymptomsarenutrientspecificandshowdifferent
patternsincrops.
Limitations:
•Thevisualsymptomsmaybecausedbymorethanonenutrient.
•Deficiencysymptomsmaybeduetoanexcessquantityof
another.
•Deficiencysymptomsinthefieldmaybeduetodiseaseorinsect
damagewhichcanproducecertainmicronutrientdeficiencies.
•Nutrientdeficiencysymptomsareobservedonlyafterthecrop
hasalreadysufferedanirreversibleloss.

29. ClearDeficiencyindicatorplants:
Plant Nutrientdeficiency
Oat :Mg, Mn and Cu deficiencies
Wheat and barley:Mg, Cu and some times Mn deficiencies
Sugar beets :B and Mn deficiencies
Maize :N, P, K, Mg, Fe, Mn and Zn deficiencies
Potatoes :K, Mg and Mn deficiencies
Rape :N, P and Mg deficiencies
Brassicaspecies:K and Mg deficiencies
grass :Fe and Mn deficiencies
Celery and
sunflower
:B deficiency
Cauliflower :B and Mo deficiencies
Flax :Zn deficiency

30. ClearToxicityindicatorplants:
Plant Nutrienttoxicity
Barley :B, Mn and Al toxicities
Cucumber :N and P excess
Sugar beets :Cu excess