Furthermore，arelativelyinferiorsoilwhichisnewlycultivatedandneverbeforetouchedbycivilisationprovidedtheclimaticconditionsarethennotcompletelyunfavourable，hasaccumulatedagreatdealofplantfoodthatiseasilyassimilated-atleastintheupperlayersofthesoil-sothatitwillyieldcropsforalongtimewithouttheapplicationoffertilisersandevenwithverysuperficialcultivation。ThewesternprairieshavetheadditionaladvantageofhardlyrequiringanyclearingexpensessinceNaturehasmadethemarable。[33a]Inlessfertileareasofthiskind，thesurplusisnotproducedasaresultofthehighfertilityofthesoil，i。e。，theyieldperacre，butasaresultofthelargeacreagewhichmaybesuperficiallycultivated，sincesuchlandcoststhecultivatornothing，ornexttonothingascomparedwitholdercountries。Thisisthecase，forinstance，wheresharecroppingexists，asinpartsofNewYork，Michigan，Canada，etc。Afamilysuperficiallycultivates，say，100acres，andalthoughtheoutputperacreisnotlarge，theoutputfrom100acresyieldsaconsiderablesurplusforsale。Inadditiontothis，cattlemaybegrazedonnaturalpasturesatalmostnocost，withoutrequiringartificialgrassmeadows。Itisthequantityoftheland，notitsquality，whichisdecisivehere。ThepossibilityofsuchsuperficialcultivationIisnaturallymoreorlessrapidlyexhausted，namely，ininverseproportiontothefertilityofthenewsoilandindirectproportiontotheexportofitsproducts。”Andyetsuchacountrywillgiveexcellentfirstcrops，evenofwheat，andwillsupplytothosewhoskimthefirstcreamoffthecountry，alargesurplusofthisgraintosendtomarket”
1，c。，p。224。Propertyrelationsincountrieswithmaturercivilisations，withtheirdeterminationofthepriceofuncultivatedsoilbythatofthecultivated，etc。，makesuchanextensiveeconomyimpossible。
Thatthissoil，therefore，neednotbeexceedinglyrich，asRicardoimagines，northatsoilsofequalfertilityneedbecultivated，maybeseenfromthefollowing。IntheStateofMichigan465，900acreswereplantedin1848towheatwhichyielded4，739，300bushels，oranaverageof101/
bushelsperacreafterdeductingseedgrain，thisleaveslessthan9bushelsperacre。Ofthe29countiesofthisState，2producedanaverageof7
bushels，3anaverageof8bushels，2——9，7——10，6——11，3——12，4——13bushels，andonlyonecountyproducedanaverageof16bushels，andanother18bushelsperacrel。c。，p。225。