soil science curriculum€¦ · soil biology respiration 2 label the information (approximately 4...
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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
Solidmanureororganicmaterialapplication
Provideadditionalcarbonandnitrogensourceformicrobestobreakdownandincreasebiomassproduction.
Increasedrespirationwhenmanurebeginstobreakdownandincreasedbiomassproduction.
Positiveimpactonsoilstructure,fertilityandsoilorganicmattercontent.
HighresiduecropsorcovercropsusedinrotationwithhighC:Nratio
HighC:Nratiocropsandaddednitrogenincreasedecompositionandaccrualofsoilorganicmatter.
HighC:Nratiocropresiduetieupnitrogentemporarilyinordertobreak down residue, increasedsoilmoisture,decreasederosion.
Positiveimpactonlongtermsoilhealth,fertilityandsoilorganicmattercontent.
Tillagesuchasannualdisking,plowing,etc.
Stirsthesoilprovidingatemporaryincreaseinoxygenformicrobestobreakdowncarbonsources.
Providesaflushofnitrogen,othernutrientsandcarbondioxidereleaseimmediatelyaftertillage.Increaseserosionrates,decompositionrate of residue, and other carbonsources.
Declinesinsoilorganicmatter,soilhealth,soilfertility.
Cropresiduemanagement
Leave residue on the surfaceincreasinggroundcovertoprotectthesoil.
Increasedcropresiduecovercantieupnitrogentemporarilyinordertobreak down residue, increasedsoilmoisture,decreasederosionandcoolersoiltemperatures.
Positiveimpactonlongtermsoilhealth,fertilityandsoilorganicmattercontent.
Nitrogenfertilizerormanureapplication
Providesnitrogen(energy)sourceformicrobestobreakdownhighC:Nratioresiduequicker.
Temporaryincreaseinrespirationduetoincreasedrateofbreakdownoforganicmaterials.
Whenmanagedcorrectly,hasanoverallpositiveimpactonsoilorganicmatterandsoilhealthbyincreasingproductionlevels and residue amounts.
Vehicleorfarmequipmenttraffic
Compactssoildecreasingporespace,watermovement,oxygenformicrobesandnitrogenlossfromdenitrification.
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
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.
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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
500-1000mgCO2/kgsoil/wk
1000-2000mgCO2/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?