Recallthatundertherentalsharerestrictionahighertenantinputcosttendstoeabout,andthatthecropschosentoberotatedwillbeselectedmoreaccordingtotheirgrossvaluethanaccordingtotheirnetworth.Equilibriumunderthesharerestrictionnolongerimpliesthemaximizationofrentalannuity.Instead,itwilltendtowardthemaximizationofyieldvalueperacreoflandperperiodoftime.[6]Withthisreasoning,threetypesofcropsaddedatthemarginaredetectedunderthesharerestriction,andIdiscusseachinturnbelow.

TheCropoftheInternalLandMargin

Theterm"landmargin"asitisusedinlandeconomicsusuallyrefersto"arable"landwhichisnotcultivated.Theinternallandmarginusedherereferstothebitsandpiecesoflandwithinaprivatelyownedfarm,thequalityofwhichissolowthatunderafreemarkettheyareseldomutilized.InTaiwan,thesemarginsincludehillslopesandbadlyerodedfields,uponwhichsomethingofvaluecouldbegrown.Underthesharerestriction,thecropchosenforthismarginallandwascitronella,awildperfumegrasswhichwasnowwidelyintroducedfororganizedcultivation.

Asisshownintable5,thecropareaforcitronellaincreasedfrom2.36thousandhectaresin1948toapeakof16.87thousandhectaresin1951.[7]Inprefectureranking,theresponseincropareaincreaseisclearlymoresignificantfortheprefecturesingroupIthanforthoseingroupsIIandIII.Theyieldpercrophectareincreasedslightlyfrom1948to1949,butgenerallydeclinedrapidlyin1950and1951.Thelargedeclineincrophectareyieldafter1949asthecropareacontinuedtoincreasemaybeinterpretedastheresultofagradualuseoflesssuitablelandmarginsforcitronellacultivation,wheretheverylowyieldofmarginalplantingpulleddowntheaveragecrophectareyield.

Presumably,thedecreaseincrophectareyieldin1950cannotbeexplainedbytheexhaustionofbetterlandmarginsalone.TakeSinchu,forexample,wherethetotalyieldin1949(5.06×10.4)wasonlyafractionlowerthanthatin1950(8.3×6.61).The64percentincreaseincropareain1950ledtoonlya4.3percentincreaseintotalyield,suggestingthattheyieldsfromincrementalcropareaweresolowthatonedoubtswhethertheland-margin-exhaustioninterpretationwouldsuffice.Plantingatarapidratemighthaveledtogenerallypoororganizationforcitronellacultivation.Ofcourse,thereisalsothepossibilityofrandomfluctuationsowingtoweather,etc.But,thefurtherdeclineinaveragecrophectareyieldin1951,withfurtherincreaseincroparea(hectare),againconfirmstheverylowyieldofmarginalplantingowingtotheexhaustionofbetterinternallandmargins.

Totheextentthatthetotalyieldonthegiven(physical)landincreasedasaresultofincreasingcroparea(plantingrate),asisclearlythecasewhenwepare1948withanyofthefollowingthreeyears(table5),[8]theaverageproductoflandhadincreased(i.e.,shiftedupward).Thisimpliesthatthemarginalproductcurveofcultivatedlandalsoincreased,owingtotheincreaseintenantinputs.Judgingfromthefactthatthetotaloutput(cropareatimesthehectareyield)increasedsignificantlymoreinprefecturesofthehigherrankings(rankedaccordingtoproportionsoffarmsaffectedbythesharerestriction),themarginalproductoflandintenantfarmsincreasedrelativetofarmsunaffectedbytherestriction.Totheextentthattheaverageyieldpercrophectaresharplydecreased,aswasclearlythecaseafter1949,themarginalyieldofincreasingtenantinputsincultivatingincrementalcrophectare(area)musthavefallentoaverylowlevel.Ifthecostoftenantinputsrequiredtocultivateeachadditionalcrophectareremainedconstantorincreased,theverylowyieldoftillingtheincrementalcropareaconfirmsthatthemarginalcostoftenantinputswashigherthantheassociatedmarginalproduct.Relatingthistotherelativeprefectureresponsesaspredictedinaccordancewiththeirranking,theevidencealsoconfirmsthatthemarginalproductoffarmingresourcesotherthanlandyieldedlowerreturnsintenantfarmsthaninownerfarms.Allthisisimpliedbythehypothesisofincreasedfarmingintensityderivedfrommytheoryofsharetenancy.

CropsoftheInterplantingMargin

Otheridentifiablemarginalcropsbehavedsimilarly.Hereletmeturntothecropsoftheinterplantingmargin.Betweentherowsofaplantedcropsomethingelsecouldbegrown.Ifanothercropisaddedinthespacebetweentherowstogrowatthesametime,itiscalledinterplanting.Ifanothercropisaddedinbetween,butcontinuestogrowaloneaftertheinitialcropisharvested,itiscalledrelaying.Torelayistointerplantpartially.