Soil Science Curriculum€¦ · Soil Biology Respiration 2 Label the Information (Approximately 4 minutes) Direct students to their Guided Notes and encourage them to capture the

Soil Science CurriculumContent and lab derived from the USDA-NRCS Guides for Educators. Go to www.nrcs.usda.gov/soils for the Guides and additional pictures and diagrams. This lesson plan was adapted for South Dakota from the University of Nebraska Institute of Agriculture and Natural Resources, CROPWATCH.

South DakotaNatural Resources Conservation Service South Dakota FFA

January 2018

Approximately 180 minutes

ObjectivesBy the end of the lesson, students will know or be able to:

•Definesoilrespirationandsoilmicrobes•Explaintheroleofsoilrespirationindeterminingsoilhealth

•Diagramtheroleofsoilrespirationinthecycleoflifeonearth

•Listandexplaininherentfactorsthataffectsoilrespiration

•Listanddescribesoilrespirationmanagementprocesses

• Interpretmanagementimpactsonsoilrespirationandsoilorganicmatter

•Measuresoilrespirationandinterpretdata

Materials•Labmaterials(seeLabGuidedNotes)•Baggiethatseals•Plantcutting

Preparatory Work•Placeaplantcuttinginaplasticbaggieseveralhourspriortoteachingthislessonsothatrespirationisvisible

Soil Biology Respiration

Soilbiologyrespirationreferstotheproductionofcarbondioxidewhensoilorganismsrespire.Thisincludesrespirationofplantroots,therhizosphere,microbesandfauna.

SoilbiologyrespirationisakeyecosystemprocessthatreleasescarbonfromthesoilintheformofCO2.CO2isacquiredfromtheatmosphereandconvertedintoorganiccompoundsintheprocessofphotosynthesis.Plantsusetheseorganiccompoundstobuildstructuralcomponentsorrespirethemtoreleaseenergy.Whenplantrespirationoccursbelow-groundintheroots,itaddstosoilrespiration.Overtime,plantstructuralcomponentsareconsumedbythebiotainthesoilwhichthenreleasesCO2.WhenthisCO2 isreleasedbybelow-groundorganisms,itisconsideredassoilrespiration.

Theamountofsoilrespirationthatoccursinanecosystemiscontrolledbyseveralfactors.Thetemperature,moisture,nutrientcontentandlevelofoxygeninthesoilcanproduceextremelydisparateratesofrespiration.Theseratesofrespirationcanbemeasuredinavarietyofmethods.

Soilbiologyrespirationratescanbelargelyaffectedbyhumanactivity.Thisisbecausehumanshavetheabilitytoandhavebeenchangingthevariouscontrollingfactorsofsoilrespirationfornumerousyears.Tillageandfertilizationbyhumansalsohasthepotentialtoaffectrespirationrates.


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Label the Information (Approximately 4 minutes)DirectstudentstotheirGuidedNotesandencouragethemtocapturethefollowinginformation.

•Soilrespirationisameasureofthecarbondioxidereleasedfromthesoilbymicrobesdecomposingsoilorganicmatterandfromtherespirationofplantroots.

•Soilrespirationindicatessoilhealth(soilorganicmattercontent,soilorganicmatterdecompositionandthelevelofmicrobialactivity).

• SoilMicrobes:Soilorganismsthatareresponsibleforsoilrespirationandmanyimportantsoilprocessessuchasnutrientcycling.

• Respiration:Releaseofcarbondioxidefromseveralsources(decompositionofsoilorganicmatterbysoilmicrobes,andrespirationfromplantroots).

• Mineralization:Organicmatterdecompositionreleasingnutrientsinaplantavailableformthatoccursduringrespiration.

• Ammonification:Productionofammoniumfromsoilorganicmatterdecomposition.• Denitrification:Anaerobicconversionandlossofnitrate-nitrogentonitriteandnitrogenvarieties ofgases.• Nitrification:Anaerobicmicrobialprocessconvertingsoilammoniumnitrogentoplant availablenitrate.

Provide the Experience – Key Terms and Soil Health (Approximately 5 minutes)Separatestudentsintosmallgroupsofthreeorfour.

Provideeachsmallgroupwithasoilsample.(Itwillbehelpfulifsomeofthesampleshavebugs,worms,cropresidueorotherlivingorganismsinthem.)

Instructsmallgroupstoinvestigatetheirsoilanddeterminewhatinthesoilaffectstherespirationthatoccursinthesoil.Elicitstudentresponses.

Enroll the Participants (Approximately 4 minutes)Showorpassaroundthesealedbaggiewiththeplantcuttinginsideofit.Inquiretostudentsastowhattheyknowaboutwhythewaterdropletsformedinsideofthebaggieeventhoughyouplacedonlyaplantcuttinginsideofthebaggie.

Holdupthesecond(empty)plasticbaggieandbreatheintoittodemonstratetheformationofwaterdropletsbecauseofyourbreath.Again,inquireaboutwhatstudentsknow.

Contenttoshare:

•Livingorganismsconducttheprocessofrespiration.•It’seasytoseesignsthatahumanisbreathing (arisingchestorabdomen,soundofbreathing,feelofbreath,etc.)•Wecanseethatplantsarebreathingthroughthecuttinginthebaggie


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Demonstrate the Relevance (Approximately 7 minutes)Instructstudentstotalktogetherandformulateideasabouthowsoilorganicmatterandrespirationaffectsoilhealth.

Elicitresponses,fillinginthefollowinginformation.

•Respirationratecanbebasedontheamountofsoilorganicmatterpresent.- Soilorganicmatterisafoodsourceformicrobesandwhenmicrobesarepresentandworking,respirationishigher.

- Whensoilorganicmatterisabsentorlow,thereislessdecomposingactivity.- Soilmicrobesareresponsibleforsoilrespirationandmayimportantsoilprocesses(suchasbacteria,fungi,protozoa,algae).

- Oneheapingtablespoonofsoilcancontainoverninebillionmicrobes,morethanallthepeopleonearth.

Sharethefollowingdiagram.Encouragestudentstocompletethediagramintheirguidednotes.

Provide the Experience – Factors Affecting Soil Respiration (Approximately 5 minutes)Instructstudentstoworkinsmallgroups.Provideeachsmallgroupwithoneofthefollowingfactorsthataffectsoilrespiration.Instructstudentstodiscusshowtheirgroup’sfactormightaffectsoilrespiration.

Factors: Climate/Weather Biologicalactivity Soilmoisture Amountandhealthofsoilorganicmatter Soil texture

Plants

Food+OxygenSunWater+CarbonDioxoide

Soil


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Label the Information (Approximately 7 minutes)SoilRespirationManagementPractices

1.Leavecropresiduesonthesoilsurface.a.ResidueswithlowC:NratiosdecomposefasterthanthosewithhighC:Nratiosb.Highresiduecrops+addedNitrogen=higherdecompositionratesandaccrualoforganicmatter

2.Useno-tillpractices.a.Tillingdecreasessoilbiologywhichthenslowsdecompositionoforganicmatterb.Minimizeequipmentuseinfieldsc.Minimizefarmequipmentuseingeneralwhensoilsarewetd.Usedesignatedlocationsforequipmenttraffic

3.Usecovercrops.a.Rootsproviderespiration

4.Addorganicmatter.a.Nourishesmicrobes

5.Plantlongseasoncrops.a.Providesalivingrootfortheentiregrowingseasontomaximizesoilbiology

Demonstrate the Relevance (Approximately 5 minutes)Facilitateadiscussionwithyourstudentsaboutthelargereconomiceffectsofpoorsoilrespiration.Dependingonthedemographicsofyourstudents,usereferencesthatmakesensetothem–farmingorfromthestandpointofaconsumer.Considerusingthefollowingquestionsasaguide:

Howcanpoorsoilrespirationaffectafarmerwhoseincomedependsonthecropgrowninthatsoil?Howcanpoorsoilrespirationaffectthepricesweseeforourfoodinthegrocerystore?

Provide the Experience – Soil Respiration Management (Approximately 3 minutes)Continuethefacilitateddiscussionbyaskingthefollowingquestion:

Whatdoyouthinkwecandoasproducersandconsumerstoensureaproductivesoilrespirationrate?

Label the Information (Approximately 10 minutes)•Climate/Weather

-Cannotbechanged-Affectstemperature,moistureandindirectlyaffectsbiologicalactivity

•Biologicalactivity-Varieswiththeseasonsandtimesofday

•Soilmoisture-Asmoistureincreases,respirationratesincreaseuntiltheporesareoverlysaturated,resultinginloweroxygencontentandlowersoilorganismrespiration-Sixtypercentporespacesaturation(fieldcapacity)isidealforrespiration-Drysoilshavelowrespirationratesbecauseoflesssupportforbiologicalactivities

•Amountandhealthofsoilorganicmatter-Affectsmicrobeactivity

• Soil texture-Clay–soilorganicmatteris“protected”fromdecomposition-Sand–toolittleorganicmatter-Mediumtexture(siltandloam)–favorableforsoilrespiration


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Demonstrate the Relevance (Approximately 15 minutes)DirectstudentstothefollowingchartintheirGuidedNotesandinstructthemtolistsomeshorttermandlongtermimpactstheycanthinkofforeachmanagementpracticeandapplication.Usethekeybelowtofacilitatethediscussionafterashorttime.

Management Practice

Application Short Term Impacts Long Term Impacts

Solidmanureororganicmaterialapplication

Provide additional carbonandnitrogensourceformicrobestobreakdownandincreasebiomassproduction.

HighresiduecropsorcovercropsusedinrotationwithhighC:Nratio

HighC:Nratiocropsandaddednitrogenincreasedecompositionandaccrualofsoilorganicmatter.

Tillagesuchasannualdisking,plowing,etc.

Stirsthesoilprovidingatemporaryincreaseinoxygenformicrobestobreakdowncarbonsources.

Cropresiduemanagement

Leave residue on the surfaceincreasinggroundcovertoprotectthesoil.

Nitrogenfertilizerormanureapplication

Providesnitrogen(energy)sourceformicrobestobreakdownhighC:Nratioresiduequicker.

Vehicleorfarmequipmenttraffic

Compactssoildecreasingporespace,watermovement,oxygenformicrobesandnitrogenlossfromdenitrification.

Table 1.InterpretingmanagementimpactsonsoilrespirationandSoilOrganicMatter(SOM).


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Management Practice Application Short Term Impacts Long Term Impacts


Provideadditionalcarbonandnitrogensourceformicrobestobreakdownandincreasebiomassproduction.

Increasedrespirationwhenmanurebeginstobreakdownandincreasedbiomassproduction.

Positiveimpactonsoilstructure,fertilityandsoilorganicmattercontent.



HighC:Nratiocropresiduetieupnitrogentemporarilyinordertobreak down residue, increasedsoilmoisture,decreasederosion.

Positiveimpactonlongtermsoilhealth,fertilityandsoilorganicmattercontent.



Providesaflushofnitrogen,othernutrientsandcarbondioxidereleaseimmediatelyaftertillage.Increaseserosionrates,decompositionrate of residue, and other carbonsources.

Declinesinsoilorganicmatter,soilhealth,soilfertility.



Increasedcropresiduecovercantieupnitrogentemporarilyinordertobreak down residue, increasedsoilmoisture,decreasederosionandcoolersoiltemperatures.

Positiveimpactonlongtermsoilhealth,fertilityandsoilorganicmattercontent.



Temporaryincreaseinrespirationduetoincreasedrateofbreakdownoforganicmaterials.

Whenmanagedcorrectly,hasanoverallpositiveimpactonsoilorganicmatterandsoilhealthbyincreasingproductionlevels and residue amounts.



Decreasesrespiration,yields,waterinfiltrationandincreasesrunoff.

Productiondeclines,increasedsoilerosionandrunoff,decreasedsoilhealth,compactedsoilsandreducedmicrobialactivity.


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Provide the Experience – Measure and Interpret Soils Respiration(Approximately 90 minutes)

Introduceeachofthelaboratorysuppliestothestudentsandreviewthelaboratoryprocessesandprocedureswiththeclass.SeetheGuidedNoteslabforinformation.

Studentsengageinthelabactivity.

Label the Information (Time varies)Studentsrecordinformationandanswerlabquestions.

Demonstrate the Relevance (Time varies)Discusswithstudentshowtheiractivitiesaffectsoilrespirationrates.

Review the Content (Approximately 7 minutes)Instructstudentstoworkinsmallgroupstocreateajinglethatincludesaminimumofthreefactstheylearnedduringthesoilrespirationlessonandlaboratoryactivity.Studentssharetheirjinglewiththeclass.

Celebrate Student Success (Approximately 3 minutes)Thankstudentsfortheirengagementandparticipation.


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Guided Notes: Soil RespirationNotescompletedby___________________________

SoilMicrobes:

Respiration:

Mineralization:

Ammonification:

Dentrification:

Nitrification:


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•Climate/Weather

•Biologicalactivity

•Soilmoisture

•Amountandhealthofsoilorganicmatter

• Soil texture

Factors Affecting Soil Respiration Soil Respiration Management Practices

1.Leavecropresiduesonthesoilsurface.

2.Useno-tillpractices.

3.Usecovercrops.

4.Addorganicmatter.

5.Plantlongseasoncrops.

6.Drainwetsoil.


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Table 1.InterpretingmanagementimpactsonsoilrespirationandSoilOrganicMatter(SOM).

Management Practice

Application Short Term Impacts Long Term Impacts


Provide additional carbonandnitrogensourceformicrobestobreakdownandincreasebiomassproduction.












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Guided Notes: Soil Respiration LaboratorySoil Respiration Scenario

TomandMollyaretroubledabouttheperformanceafieldtheyrecentlypurchasedandplantedtocorn.Thefieldwashighlytilledwithlittlecropresidue.Theequipmentusedonthefieldbythepriorownerhadverynarrowtires,andthereisnoconsistentpathusedfortravelingtotheirrigationpad.Theyarecuriousaboutwhatmightbetheproblemandplantotestthesoilrespirationratetoday.

Laboratory Supplies

•Solvita®samplejarforcorrectvolumeofsoilora3-inchdiameteraluminumcylinderandlid•Foil-packcontainingaspecialgelpaddle•Solvita®keyforreadingresults•Solvita®interpretationguidetoestimatedifferencesinsoilhealth,respirationandpotentialnitrogenrelease

•Aluminumfoilorcapwhenaluminumcylinderisused•Solvita®soilliferespirationtest(paddles)•Soilthermometerorcontrolledroomtemperature•Smallplasticbucketforeachgroupofstudents•Baggieswithazipperclosure

Laboratory Steps

Whensoilsaremixed,respirationtemporarilyincreasesbecauseoftheaerationcausedbymixing.Thisissimilartothetemporaryincreaseinrespirationcausedbytillage.Asoxygenavailabilityincreases,organicmatterbreaksdownquicker.

Considerusinganintactsoilcoreinthe3-inchdiameteraluminumcylinderratherthanmixingsoil.Anintactcorebetterreflectsrespirationforno-tillapplications,whileamixedsamplewillbetterreflectrespirationeitherimmediatelyaftertillageorposttillage(atleastonedayaftermixing).Togetanaccuratecomparisonofdifferentmanagementsystems,severalsoilsamplesrepresentingdifferentmanagementsystemscanbecompared.


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Step-by-Step Procedure 1.SoilSampling-Gatheraminimumof10smallsamplesfromanareathatrepresentssimilarsoiltypeandmanagementhistorywithaprobefromthesurface0-6inchdepth.Placethesamplesinthesmallplasticbucket.Repeatthisstepforeachsamplingarea.

(Soilrespirationisvariable,bothspatiallyandseasonally,andisstronglyaffectedbyorganicmatter,manureapplications,oxygenlevels,soilmoisture,salinityandsoiltemperature.Usefreshsoilsamples,gatheredjustbeforethetest.)

2.Mixing-Mixsoilintheplasticbucketjustwellenoughtobehomogeneousandremoveroots,residue,largestonesandresiduesfromsampleandplaceinalabeledplasticzipbag.

3.AddWaterifNeeded-Thesampleshouldhaveidealmoisture(nearfieldcapacity)forgrowingconditions.Iffieldconditionsaredryitisbesttoaddwater24hourspriortosampling.Ifneeded,watercanbeaddedpriortostartingthetestintheclassroom.

4.PutSampleIntoSolvita®Jar-ShortlyaftersamplingputmoistmixofsoiluptofilllineintheSolvita®jar.Asyoufill,tapthebottomofthejaronahardsurfacetoensuretherearenovoids.

5.UsetheColorGel-Insertcolorgelpaddleintosoilwiththegelfacingoutnexttotheclearsideofthejar.Becarefulnottojostleortipthejar.Screwthelidonverytightlyandrecordthetimeonthelid.Keepthejarintheclassroomatacontrolledtemperatureof68-75degreesFahrenheitandoutofsunlightfor24hours.

6.ReadandRecordResults-Readgelcolorafter24hoursandrecordresultsonTable3. 7.AnswerdiscussionquestionsandcompleteinterpretationssectionofTable3.RefertoSolvita®soiltestinstructionsforadditionalinformationandinterpretations.

Interpretations

Respirationlevelsreflectsoilhealthbasedonthelevelofcarbondioxiderespiration.Ratesareimpactedbythehealthofsoil,soilorganicmattercontent,andcanbeusedtoapproximatequantityofnitrogenreleasedperyearinanaverageclimate.TherateofcarbondioxidereleasedisexpressedasCO2-Clbs/acre-3”/day.

Highsoilrespirationratesareindicativeofhighbiologicalactivity.Thiscanbeagoodsignofahealthysoilthatreadilybreaksdownorganicresiduesandcyclesnutrientsneededforcropgrowth.Solvita®responsemaygofromaninactivecondition(0-1blue-gray)toaveryactivestate(3.5-4.0green-yellow)assoilrespirationincreasesfromdesirablemanagementmeasuressuchasdiversecroprotations,andno-till.

Insomecases,heavilymanuredsoilsorsoilshighinorganiccontentcanattainaveryhighrate(5yellow).Thiscanbedetrimentalwhendecompositionofstableorganicmatteroccurs.Itisgenerallydesirabletohaveatleastgreencolor3.Ittypicallytakesseveralyearsforasoiltoimprovefromalowbiologicalstatustoamoreactiveone.Withproperresiduemanagement,diversecroprotations,organicmatteradditionsandavoidanceofdestructivetillagepractices,thetimetoreachamoreoptimumconditionisshortened.


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Table 2.Basicsoilbiologicalhealth

Solvita Test - Color/Colorimetric Number

0-1Blue-Gray

1.0-2.5Gray-Green

2.5-3.5Green

3.5-4.0Green-Yellow

4-5Yellow

Soil Respiration Activity

VeryLowSoilActivity

Moderately Low Soil Activity

MediumSoilActivity IdealSoilActivity UnusuallyHighSoilActivity

Associatedwithdrysandy soils, and littleornoorganic

matter

Soilismarginalintermsofbiologicalactivityandorganic

matter

Soil is in a moderately

balancedconditionand has been

receivingorganicmatteradditions

Soiliswellsuppliedwithorganicmatterandhasanactivepopulationof

microorganisms

High/Excessiveorganicmatter

additions

*Approximate Level of CO2 - Respiration

<300mgCO2/kgsoil/wk

300-500mgCO2/kgsoil/wk



>2000mgCO2/kgsoil/wk

<9.5lbsCO2-C/acre-3”d

9.5-16lbsCO2-C/acre-3”d

16-32lbsCO2-C/acre-3”d

32-64lbsCO2-C/acre-3”d

>64 lbsCO2-C/acre-3”d

Approximate Quantity of Nitrogen (N) Release Per Year (Average Climate)

<10lbs/acre 10-20lbs/acre 20-40lbs/acre 40-80lbs/acre 80->160lbs/acre

*Source:Doran,J.(2001)USDA-ARSSoilHealthInstitutecorrelationofSolvita®andfieldsoilrespiration.Calculationsbasedona3-inchsoilcore(7.6cm).


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Table 3. Soilrespirationlevelsandinterpretations.

Sample Site

Median 24-hr Soil or Room

Temp.

Time-frame

Start Time

End Time

Gel Color & Colorimetric

Number

Soil Activity Rating

(Table 1)

Avg. Respiration

Level lbs CO2-C/acre-

3”/d

Quantity of N

Released lbs/ac/yr

Whatdidyouexpectintermsofthesoilrespirationlevels?

Whatsurprisedyouaboutthesoilrespirationlevels?

Whatdoyouexpecttohappentothesoilorganicmatterbasedonthesoilrespirationrates?(improve,decline,remainthesame)Why?

Documents

Soil Science Curriculum€¦ · Soil Biology Respiration 2 Label the Information (Approximately 4 minutes) Direct students to their Guided Notes and encourage them to capture the