The structural role of flowing carbon Everybody knows the presence of carbon is important for soil structure, however, it also has a structural role. This comes back to carbon being the main building block of pastures. By structural role, I mean the way paddocks are more water efficient and have increased capacity to capture resources when plants are physically present. The wick effect Carbon has a structural role as part of plant the roots. Roots, which are 45% carbon, act as “wicks” to take water down through the soil profile, especially important with harder soils. This is achieved by water travelling down beside roots. Better managed plants, with more extensive root systems, distribute water faster through the soil and to greater depth. Root response to different grazing pressure 1 – Grazed 6 times at 1-leaf stage 2 – Grazed 3 times at 2-leaf stage 3 – Grazed twice at 3-leaf stage
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The structural role of flowing carbon
Everybodyknowsthepresenceofcarbonisimportantforsoilstructure,however,italsohasastructuralrole.Thiscomesbacktocarbonbeingthemainbuildingblockofpastures.
Bystructuralrole,Imeanthewaypaddocksaremorewaterefficientandhaveincreasedcapacitytocaptureresourceswhenplantsarephysicallypresent.
Thewickeffect
Carbonhasastructuralroleaspartofplanttheroots.Roots,whichare45%carbon,actas“wicks”totakewaterdownthroughthesoilprofile,especiallyimportantwithhardersoils.
Thisisachievedbywatertravellingdownbesideroots.Bettermanagedplants,withmoreextensiverootsystems,distributewaterfasterthroughthesoilandtogreaterdepth.
Root response to different grazing pressure
1–Grazed6timesat1-leafstage
2–Grazed3timesat2-leafstage
3–Grazedtwiceat3-leafstage
Restingpasturesforashortperiodafterrainincreasescarbonflowsforrootconstruction,whichinturnimprovestheinfiltrationoffuturerain.
Withperennialgrasses,therootsgrowanddieback.Thisresultsincavitieswhererootshavepreviouslybeen.Thesecavitiesareveryeffectiveforwaterinfiltration.
Rootshelpsecurenitrogen
Wherepasturesarenotfertilised,thenitrogenpresentinthesoiloriginatesfromtheearth’satmosphere,whereitmakesupabout78%oftheair.Eachhectareoftheearthiscoveredbyabout84,000tonnesofnitrogenintheatmosphere.
Nitrogencomesinwithrain,soinfiltrationdeterminesplantavailablenitrogenfromthissource.InthetallgrasssavannahsoftheNorthernTerritoryofAustralia,eachyearrainbringsin2kgofnitrogenperhectare.Toputthisintoperspectiveinthisarea,attheendofthegrowingseasonthereis10-15kgofnitrogeninstandinggrass,whichislowcomparedwithmorefertileareas.
Thereseemstobeatrendtowardsmoreintenserainfallevents,whichiswhyimprovingwaterinfiltrationisevenmoreimportant.
Liftingwind&shading
Haveyouevergivenanythoughttowhyclothesonthelinedryquickeronawindydaythanonastillone?Goingbacktobasics,moistureisreleasedfromthewetclothesintothedrierairaroundthem.Whentheimmediateairbesidetheclothesissaturated,nomoremoistureisreleasedfromtheclothes.Thewinddriestheclothesbecauseitblowsawaythemoistairandreplacesitwithdrierair,whichthenabsorbsmoremoisturefromtheclothes.
Theclotheslineprincipleiscentraltoanotherstructuralroleofcarbon.Standingplantsliftwindoffthesoilsurfacewhichslowsthedryingofsoil.
Shadingbyplantsisanimportantcomponentofwateruseefficiency,asitslowsevaporationandmakesmorewateravailabletoplants.
Maintainingthepopulationofsoilmicrobesovertime
Alotofsoilmicrobesarelikeperennialgrasses,inthattheyhavetogointodormancywhenconditionsarenotfavourable.
Whenthesoildriesquickerthanitshould,thisdoesnotgivesoilmicrobestimetogothroughtheirnormalprocessofgoingintodormancyandsotheydie.
Thesoilremainingdryforalongtimeduringdroughtsisnotanissuefordormantmicrobes.MicrobesfoundinthetombsofEgypthavebeenreactivated.
Collectingdew
Anotherstructuralroleofcarboniscollectingdewinsomeenvironments.Thisreliesonthesurfaceareaofgrassbeingadequate.
Germanscientist,DrWihelmRiplexplainswhyplantsareresponsibleforgreateravailabilityofwatertothelandscape,“Watervapourintheloweratmosphereclosetovegetation,evenwithoutasinglerainevent,canbeprecipitatedbyleaves,needlesandotherstructureswithhighsurfacetovolumeratios.Theresultisaloweringofsurfaceenergyandawarmingofthesestructures.”
Inthecaseoffrosts,formoisturetoaccumulateonthesoilsurface,therehastobeenoughmoisturefrozenthenthawedasthesunrises.Inanareasufferingthedriestwinterinyears,Iobservedthattherewasregularlymoistureonthegroundatthebaseofplantsafterthesunhadrisen.Thisphenomenonwasonlyoccurringwherethegrasswasthickandtall.Itwasactuallymaintainingsomegreenleafatthebasewhereitwasprotectedfromfrost.
Conclusion
Thestructuralroleofcarbonreliesonthefastermovingcarbonresidinginplants,whichinturnreflectsthemanagementofcarbonflowsfromwhatraindoesarrive.
Managementthatleadstobetterwaterinfiltrationviaincreasedrootsandthenslowerdryingofthesoilsurfaceduetowindbeinglifted,increasesgermination.
RootsplayaveryimportantroleinReefprotection.Waterhasvolumeandifitgetstogetherandgathersspeed,thenthatiswhenitdoesdamagebyerodingsoilandcarryingnutrientsintowaterways.Gettingmorerainfallintothesoilreducesthisproblem.Also,morestandingpasturehelpskeepwaterapartandfromgatheringspeed.
30November,2017
Next week’s discussion: “Financial analogy”.
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