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A sustainable model for the management of olive orchards located in semi-arid marginal areas: Some remarks and indications for policy makers

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A sustainable model for the management of olive orchards located in semi-arid marginal areas: Some remarks and indications for policy makers
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  A   sustainable   modelfor   themanagementofoliveorchardslocatedinsemi-aridmarginal   areas:   Someremarksandindicationsfor   policy   makers  AssuntaMaria   Palese a, * ,   MariaPergola a ,   MariafaraFavia b ,   Cristos   Xiloyannis a ,GiuseppeCelano a a Dipartimento   di   Scienze   dei   Sistemi   Colturali,   Forestali   e   dell’Ambiente,   Universita` degli   Studi   dellaBasilicata,   Viale   dell’Ateneo   Lucano,10    –   85100   Potenza,   Italy b Dipartimento   Tecnico   Economico    per   la   Gestione   del   Territorio    Agricolo,   Forestale   Universita` degli   Studi   della   Basilicata,Viale   dell’Ateneo   Lucano,   10    –85100   Potenza,   Italy 1.   Introduction Olive   ( Olea   europaea   L.)   finds   thebest   climatic   conditions   for   itsgrowth   in   the   Mediterranean   Basin   countries   where   itis   themost   widespread   fruit   tree   crop   (around   9.5   Mha   in   2010)(FAOSTAT,   2012).Awide   variety   of    olive   growing    systems   exist   in   such   alargearea   depending    on   pedo-climatic   conditions,   social,   economicand   institutional   driving    forces.   Referring    to   Europeancountries   (Beaufoy,   2002;   Various   Authors,   2006;   Duarteet   al.,   2008;   Go´mezet   al.,   2008;   Metzidakis   et   al.,   2008;Xiloyannis   etal.,   2008),some   of    these   cultivation   systemsare   characterised   by   intensive   agronomical   techniques   and e   n   vi   r   o   n   men   tals   ci   e   n   ce&   po   li   cy   2   7   (2013)   81–   9   0 a   r   t   ic   l   ein   f   o Publishedonline23   December2012 Keywords:Oleaeuropaea L.EconomicanalysesVegetalresiduerecycling CO 2  stocksCO 2  emissionstrading Europeanenvironmentalpolicy a   bst   r   a   ct Traditionalolivegrowingcansurviveonlyby   improvingolivefarmer   income   and   recogniz-ingits   multifunctionalrole.In   thisstudy,wepropose   a   sustainablemanagementmodelwhichentailstherecyclingofurbanwastewateranditsdistributionby   dripirrigationandtheuseofsoilmanagementtechniquesbased   ontherecyclingofpolygeniccarbonsourcesinternaltotheoliveorchard   (covercrops,pruningmaterial).Themodelwasappliedfora   8-yearperiodinanoliveorchardlocatedin   asemi-aridmarginalareaofSouthernItaly.Ananalysisisperformedtoevaluatetheeconomicalsustainabilityof    the   proposedmodelincomparisontotheconventionalmanagementsystem(rainfedconditions,tillage,empiricalfertilization,biennialpruningandprunedmaterialburning).Furthermore,thestudyassessestheenvironmentalbenefitscoming    fromthe   applicationoftheexaminedorchardmanagementsystemsfocusingespeciallyon   CO 2  stocksinplantsandsoil,and   anthropo-genicandnaturalCO 2  emissions.The   sustainablemodelappearsproductiveandprofitable,sociallyand   environmentallysustainable.The   significantincome   receivedeveryyearbyolivegrowers   canpersuadethemtoremainintheterritorylimitingtheurgentphenomenaoforchardabandonment,preservingtypicallandscape,and   carryingout   anecologicalcontrolroleagainstlanddegradationprocesses. # 2012ElsevierLtd.Allrightsreserved.* Correspondingauthor .   Tel.:+39   0971205274;fax:+39   0971   205378;mobile:+393470055234.E-mailaddresses:assunta.palese@unibas.it,   dinapalese@hotmail.it(A.M.Palese).  Abbreviations: CAP,CommonAgriculturalPolicy;CO 2 ,carbondioxide;CO 2 eq,   carbondioxideequivalent;CS,ConventionalSystem;EC,CommissionoftheEuropeanCommunities;EU,EuropeanUnion;FC,FixedCosts;GP,GrossProfit;NEP,NetEcosystemProductivity;NPP,NetPrimaryProductivity;PC,   ProductionCosts;SOC,soilorganiccarbon;SS,SustainableSystem;TO,TotalOutput;VC,VariableCosts. Available   online   at   www.sciencedirect.com journalhomepage:   www.elsevier.com/locate/envsci 1462-9011/$–see   front   matter #   2012ElsevierLtd.Allrightsreserved.http://dx.doi.org/10.1016/j.envsci.2012.11.001  they   are   proven   to   be   effective   with   respect   to   landproductivity   and   economic   profitability,   but   they   are   restrictedin   flat   and   irrigated   lands.   Semi-intensive   and   extensive   olivegrowing    systems   prevail   instead   in   hilly   and   mountainous   aridregions.   Extensive   systems,   inparticular,   are   characterised   bylow   inputs   of    labour   and   materials.   They   show   low   productiv-ity   too,   because   ofseveral   limiting    factors   such   as:   difficultmechanization   in   sloping    lands,   old   and   big-size   olive   trees,low   density   plantation,   unfertile   soils,   low   rainfall   and   scarcityof    water   for   irrigation.   From   asocio-economic   point   ofview,these   systems   are   mostly   characterised   bysmall   size   farming oriented   to   self-consumption   or   to   the   local   market   (FaviaandCelano,   2005;   Duarte   etal.,   2008).Furthermore,   low   productiv-ity   is   coupled   with   high   labour   costs,   mainly   due   to   thedifficulty   in   finding    specialized   workers   required   for   manualoperations   (harvesting    and   pruning).   Finally,   the   extensiveolive   groves   are   especially   exposed   to   abandonment   asconsequence   of    several   interacting    causes:   on   one   hand,   thedecoupling    of    farmer   income   aid   after   the   Fischler   reform   of the   Common   Agricultural   Policy   (CAP)   (Severini,   2006),   and,   onthe   other,   the   demographic   decline   and   the   farmers   ageing,occurring    in   more   marginal   areas   as   inthe   case   studypresented   here.   Abandonment   and   itsnegative   effects(erosion,   fires,   over-grazing,   biodiversity   losses)   have   beenexasperated   by   the   so-called   Health   check   oftheCAP(Commission   of    the   European   Communities,   2008)   and,particularly   in   Italy,   bythe   conversion   ofthehistoric   supportmodel   into   the   regional   model   in   the   olive   sector.   Thesechanges   could   determine   the   consequent   shift   ofeconomicresources   from   this   sector   to   others   with   seriously   impacts   onthe   revenues   ofolive-growing    farms   thatoften   are   uncertain(Roselli   et   al.,   2008).The   abandonment   ofolive   orchards   is   already   causing significant   effects   onland   degradation   processes   in   olivespecialized   areas   which   should   be   reinforced   because   Medi-terranean   regions   are   particularly   vulnerable   to   the   impacts   of climate   changes   and   the   severity   of    extreme   weather   events.Such   changes   are   expected   to   put   atriskcrop   yields,   thelocation   of    production,   in   addition   to   the   depletion   of    soilorganic   matter   and   to   the   worsening    ofthe   quality   andavailability   of    water   resources,   already   traditionally   scarce,   forirrigation   (EC,   2009).In   order   to   address   such   scenarios,   during    the   last   decadeEU   has   implemented   some   measures   into   the   CAP,   such   ascross-compliance   and   rural   development,   that   are   alreadyhelping    to   reduce   greenhouse   gas   emissions   from   theagriculture.   In   particular,   the   CAP   is   aiming    to   modernizefarms   with   energy-efficient   equipments   and   buildings;   to   helpfarmers   to   better   understand   and   meet   the   EU   rules   forenvironment   bymeans   of    training    and   advisory   services;   toprovide   support   for   biogas   and   to   offer   compensation   for   theextra   costs   incurred   by   farmers   who   voluntarily   favour   theprotection   of    the   environment   (agri-environmental   schemes).Regarding    the   European   water   policy,   it   is   continuouslyevolving    towards   astrategy   facing    water   scarcity   (Commissionof    the   European   Communities,   2007;   Farmer,   2010)anddrought   up   to   integrating    water   issues   in   sectoral   and   regionalpolicies   and,   in   the   first   place,   into   the   two   CAP   pillars(agriculture   and   rural   development)   (EC,2012).At   this   regard,the   last   action   plan,   Blueprint   to   Safeguard   Europe’s   Water,adopts   a   systemic   approach   combining    avariety   of    instru-ments   to   regulate   the   water   demand,   saving    and   its   efficientuse.   Even   ifwater   pricing    remains   the   market   key   tool,increasing    attention   is   being    paid   to   economic   incentives   tothe   farmers   providing    ecosystem   services,   and   to   the   reuse   of wastewater   for   irrigation.   Wastewater   reusing    provides   wideeconomic   and   environmental   benefits   such   as:   lower   energycosts   compared   to   deep   groundwater   exploitation   or   desali-nation,   abatement   in   nutrient   removal   costs   to   protect   thesurface   waters   through   irrigation   and   in   nutrient   discharge   tothe   environment,   etc.   (Durham   etal.,   2005).More   generally,   the   emergency   and   pervasiveness   of environmental   issues   in   theEuropean   growth   strategyrequires,   inter   alia ,investments   in   knowledge   and   reductionof    the   gap   between   science   and   policy   makers.   This   paperattempts   to   provide   apartial   contribution   in   this   directionsuggesting    some   guidelines   to   a   more   sustainable   manage-ment   ofextensive   olive   groves   than   thetraditional   andconventional   ones,   commonly   adopted   in   sloping    and   semi-arid   areas   ofMediterranean   countries.   The   guidelines   are   theoutcome   of    a8-year   (2001–2008)   testing    period   ofamodelbased   on   two   cornerstones:   the   reuse   of    urban   wastewaterdistributed   by   drip   irrigation,   and   therecycling    ofpolygeniccarbon   sources.   The   experiment   was   carried   out   in   anoliveorchard   placed   in   a   hilly   and   marginal   zone   of    Southern   Italy.An   economic   analysis   was   carried   out   in   order   to   assess   theprofitability   of    the   proposed   model.   In   addition,   the   researchevaluated   the   possible   environmental   benefits   coming    fromthe   application   ofthe   examined   orchard   managementsystems   focusing    especially   on   carbon   fate. 2.   Materials   and   methods 2.1.   The   experimental   context The   trial   was   performed   in   Ferrandina   (Matera   Province,Basilicata   Region,   Southern   Italy,   40 8 29 0 N,   16 8 28 0 E)   where   olivetree   represents   the   dominant   crop.   Olive   plantations   aregenerally   set   in   hilly   areas   and   grown   under   rainfed   condi-tions.   Except   for   very   few   cases,   the   olive   farm   size   isaround1   ha.   In   particular,   these   last   are   small   family   farms   managedby   hobby   farmers,   while   the   few   larger   farms   are   often   runbypart-time   entrepreneurs   (Favia   and   Celano,   2005).The   experiment   was   carried   in   a   2-ha   olive   orchard   of ‘Maiatica’   which   is   anautochthonous   cultivar   ofMateraProvince.   It   is   adual   purpose   cultivar   with   good   productivitythough   itexhibits   a   strong    alternate   bearing    behaviour.   Thedrupe   is   medium   to   large   with   ahigh   oil   yield   (around   22%   of fresh   weight)   (Rotundo   and   Marone,   2005).‘Maiatica’   oil   ischaracterised   bylow   content   of    total   phenols,   grassy   andfruity   aroma   with   alow   intensity   sensation   of    bitterness   andsharpness.   Fruits   with   specific   merceological   characteristics(big    size,   heavy   weight,   high   pulp   to   stone   ratio)   are   usuallyharvested   at   black   maturity   stage   and   then   processedaccording    to   atypical   local   method   in   order   to   obtain   oven-dried   drupes,   an   excellent   speciality   ofFerrandina   (Balat-souras   etal.,   1996;   Brighigna,   1998).Both   ‘Maiatica’   oil   andtable   olives   are   appreciated   by   consumers   and   partly   placedoutside   the   local   market,   but   table   olives   due   to   their   tipicity e   n   vi   r   o   nmen   ta   ls   ci   en   c   e   &po   licy   27(   2   013)   81–   90 82  and   the   scarce   amount   yearly   produced,   usually   fetch   apricealmost   three   times   higher   than   olives   for   oil. 2.2.   Orchard   management   systems Olive   trees   within   the   experimental   orchard   were   more   than50   year   old.   They   were   vase   trained   and   planted   at   adistanceof    about   8   m    8   m(156   plant   ha  1 ),   ascommonin   the   studiedarea.   The   climate   is   classified   as   semi-arid   with   annualprecipitation   around   561   mm(mean   1976–2006)   and   meanannual   temperature   ranging    from   15to   17 8 C.   The   soil   of    theexperimental   grove   is   asandy   loam,   classified   asa   HaplicCalcisol   (FAO,   WRB,   1998),with   alow   organic   carbon   content(7.0      3.8   g    kg   1 ,   mean   of0–0.60   m   layer    standard   deviation)and   bulk   density   of1.5   (Mg    m  3 ).In   2000,   the   olive   orchard   was   split   into   two   parts   (about0.66   ha   each)   managed   according    to   alternative   agronomicaltechniques   (Sustainable   System   –SS)   and   conventional   ones(Conventional   System   –CS).   In   particular,   the   SS   was   irrigatedwith   urban   wastewater   treated   by   apilot   unit   according    tosimplified   schemes   (Lopez   etal.,   2006;   Palese   etal.,   2009).   Thereduction   of    the   wastewater   purification   level   decreasedsignificantly   costs   ofthe   treated   water   (0.10–0.20   s m 3 versus 0.50–0.70   s   m 3 ofthecurrent   treatment   system   which   worksaccording    tothe   Italian   law   –D.Lgs.152/2006   –   fordischargeinto   surface   water   bodies   –S.   Masi,   pers.   comm.,   2011)allowing,   in   economic   terms,   its   sustainable   reuse.   Thereclaimed   wastewater   was   generally   distributed   from   Mayto   October   by   drip   irrigation   (6self-compensating    drippers   pertree,   each   delivering    8   lh  1 ).The   seasonal   irrigation   volumewas   of    3425   m 3 ha  1 year  1 (mean   2000–2008).In   SS   soil   was   not   tilled   but   covered   byspontaneous   weedsand   grasses   mowed   at   least   twice   a   year.   Irrigated   treeswerelightly   pruned   each   year.   Pruning    material   was   cut   and   left   onthe   ground   as   mulch   together   with   residues   resulting    fromcover   crop   cuts.   The   fertilization   plan   was   drawn   every   yeartaking    into   account   wastewater   and   soil   chemical   composi-tion,   and   mineral   elements   balance   in   theorchard   system(cover   crops   and   pruning    material   contributions,   potentialyield   removed   from   the   olive   grove)   (Palese   etal.,   2011).   Theaverage   amounts   ofN,   Pand   K   yearly   distributed   by   thewastewater   used   for   irrigation   were   63.0,   3.0   and   58.0   kg    ha  1 ,respectively   (2000–2008).   An   integrative   amount   of    N   (onaverage   around   40kg    ha  1 year  1 )   was   distributed   byfertirri-gation   in   order   to   entirely   satisfy   the   annual   N   plant   needs.These   last   correspond   to   themineral   element   output   from   theorchard   as   yield   and   pruning    material.   Since   pruning    residueswere   cut   and   left   on   the   ground,   they   are   considered   as   anitrogen   output   for   apercentage   equal   to   50%.   Pest   and   diseasecontrol   was   performed   according    to   the   regional   servicerecommendations   for   commercial   olive   groves.The   CS   was   grown   under   rainfed   conditions   and   managedaccording    to   the   traditional   horticultural   practices   of    the   area(tillage   performed   2–3   times   per   year,   and   empirical   soilfertilization   performed   without   considering    theplant   needsand   their   partitioning    along    thevarious   phenological   phases   of the   annual   vegetative   cycle).   Moreover,   in   this   system,   heavypruning    was   performed   every   two   years   during    the   winterafter   aproductive   year   –   aso-called   ‘on’   year.   Pruning    residueswere   removed   from   the   fieldand   burned. 2.3.   Field   measurements   and   estimations Over   theexperimental   period   (2001–2008),   in   coincidence   of each   spontaneous   vegetation   mowing,   the   fresh   weight   of    theabove-ground   biomass   ofundergrowth   was   measured   in   thefield   from   6   plots   of1   m 2 surface.   Then   data   were   referred   tohectare.   Root   biomass   fresh   weight   was   estimated   as   20%of the   above-ground   part   (Celano   et   al.,   2003).Although   roots   exudates   strongly   contribute   to   soil   carbonenrichment,   from   5to   21%   ofall   carbon   fixed   by   plantphotosynthesis   (Marschner,   1995),they   were   not   taken   intoaccount   in   this   paper   because   ofmany   uncertaintiessurrounding    their   actual   amount.In   each   experimental   year   (2001–2008),   fresh   weight   of pruning    material   and   yield   was   measured   in   the   field   on   12plants   per   treatment.Samples   ofthe   herbaceous   biomass,   pruned   material(leaves,   shoots,   branches)   and   fruits   were   taken   and   put   ina   forced-draft   oven   at   65 8 C   for   dry   matter   measurements.   Thebiomass   samples   remained   in   the   oven   until   their   weight   wasstabilized.Dried   olive   tree   organs   (fruits,   leaves,   shoots,   branches)were   analyzed   in   order   to   determine   theirN,   P   and   Kconcentrations   (expressed   as   %ofdry   matter).   The   Kjeldahlmethod   was   used   to   determine   N.   Determinations   of    P   werecarried   out   with   acolorimetric   method.   The   concentration   ofKwas   determined   by   means   of    aICP-OES   spectrometer   (iCAP6000   Series   –Thermo   Scientific)   on   samples   previouslysubjected   to   acid   digestion.   Then,   concentration   data   wererelated   to   yield   and   pruned   materials   to   determine   the   annualolive   tree   needs   for   the   fertilization   plan   drafting.Total   leafarea   was   calculatedon   three   representativeplants   persystem   by   multiplyingtheprojectedcrown   area   bythemeanleaf    density   value(4.1   m 2 m  2 )   reported   by   C ˆ erma´ket   al.(2007).The   totalleafbiomass(kg    plant  1 )   was   estimatedusing    a   meanspecificleafmass(180   g    m 2 )   asreported   byConnorand   Fereres   (2005).Theamountof    fallenoliveleavesper   plantwas   estimatedconsidering    aleafmeanlifebeforeabscissionof    2.5   years   (Connorand   Fereres,   2005).The   average   annual   increase   ofolive   permanent   structures(branches,   trunk,   stump,   roots)   was   not   taken   into   account   inthis   study.   Indeed,   Almagro   et   al.   (2010)   reported   for   a100-years   old   olive   grove   (10   m      10m)   an   annual   increase   ofonly2   kg    plant  1 on   dry   matter   basis.Annual   root   production   ofolive   trees   was   estimated   asthe50%   of    the   annual   net   dry   matter   production   (pruning material,   senescent   leaves,   yield)   asthe   mean   of    data   reportedby   Cannell   (1985)   for   other   species.   Assuming    steady   stateconditions   for   the   living    root   system,   the   input   of    dead   rootsinto   the   soil   is   equal   to   root   production   (Aerts   et   al.,   1992).Because   ofthe   alternating    characteristic   ofpruning    opera-tions,   the   annual   root   biomass   produced   by   the   CS   wasassessed   by   dividing    into   two   the   biennial   amount   of    pruning material.In   order   to   evaluate   drupe   quality   and   itspotential   marketdestination   (for   oil   ortable   consumption),   fruit   samples   weretaken   in   productive   years   at   harvest   from   trees   belonging    toboth   treatments,   SS   and   CS.   Fresh   weight   ofthe   whole   drupe,the   pulp   and   the   stone,   and   longitudinal   and   equatorialdiameters   were   measured.   Fruit,   pulp   and   stone   were   dried   to env   i   r   o   n   m   en   t   als   ci   ence&p   o   licy27(   2013)   81–90 83  aconstant   weight   at   65   8 C   in   aforced-draft   oven.   Pulppercentage   and   flesh   to   stone   ratio   were   also   determined   onfresh   weight   basis. 2.4.   Economic   analysis The   objective   of    the   economicanalysis   was   to   compare   theprofitability   of    the   twosystems.   For   this   purpose,   technicalcoefficients   were   yearly   collected   on   the   experimental   orchardsthroughout   the   2001–2008   period   (yields,   labour   and   materialinputs,   use   of    fixedcapital)   and   then   they   wereconverted   intoeconomic   information,   imputing    them   prices   and   tariffsrecorded   on   the   marketplace   of    Ferrandina   in   the   2009/2010harvesting    campaign.   Processed   data   were   integratedwithadditional   information   acquired   aftersample   surveys   on   localfarms   and   olive   mills(Favia   andCelano,2005;   Favia   andPietragalla,   2005)   and   then   validated   trough   in-depth   interviewsto   agricultural   stakeholders,   extension   service   andmarketoperators   (40   questionnaires   acquiredin   about   three   months).Economic   results   were   expressed   at   constant   values   by:Gross   Profit   ð GP Þ   ¼ Total   Output   ð TO Þ   Production   Costs   ð PC Þ where   TO   is   the   revenue   from   sales   of    oil   and   table   olives   andPC   are   the   sum   ofVariable   andFixed   Costs,   gross   of    taxes   andoverheads.Variable   Costs   (VC)   include:   specific   inputs,   wages   forseasonal   workers,   plus   interests   on   the   previous   items.   FixedCosts   (FC)   include:   depreciation,   maintenance   and   insuranceof    machines,   tools,   equipments   and   land   improvements,wages   for   permanent   workers,   rent,   and   interests   on   fixedassets.Measuring    economic   performances   through   the   GP   allowedto   take   into   account   asmany   costs   as   possible,   under   theconstraint   of    collected   data   reliability   and   regardless   of    farmtype   (family   or   non   family   farm).   However,   ithas   beennecessary   the   assessment   of    some   budget   items   through   theiropportunity   costs.   It   was   the   case   ofthe   remuneration   of family   labour   andland   ownership:   the   first   was   equated   toextra   farm   labour,   the   second   one   was   estimated   on   the   basisof    updated   cadastral   value   of    1   haof    olive   grove,   irrigated   andrainfed,   at   a   rent   rateof    2%   (De   Benedictis   and   Cosentino,1979). 2.5.    Annual   Net   Primary   Productivity   (NPP) Annual   Net   Primary   Productivity   (NPP),   expressed   asCO 2 (t   ha  1 year  1 ),was   calculated,   year   by   year,   bymultiplying    thedry   weight   of    cover   crop   residues   (above   and   below-groundparts),   pruning    material,   senescent   leaves,   yield   and   estimatedroot   biomass   of    olive   trees,   as   previously   described   (Section2.3),   with   the   conversion   factor   1.755   obtained   taking    intoaccount   the   CO 2  molecular   weight   and   the   following    relations(Robin,   1997):1   g    of    C   ¼   3 : 67   goffixed   CO 2  (1)and1   g    of    dry   matter   ¼ 0 : 4782   g    ofC   (2) 2.6.   Soil   C-CO 2  variations The   CO 2  storage   in   soil   was   calculated   starting    from   soilorganic   carbon   (SOC)   content   measured   on   the   2   mm   fractionof    samples   taken   in   triplicate   from   both   SS   and   CS   at   3different   depths   (0–0.10   m;   0.10–0.30   m;   0.30–0.60   m)   in   2000,before   the   beginning    of    the   experiment,   and   in   2008.   SOCanalyses   were   performed   on   each   sample   by   means   of    Walkleyand   Black   method   (MIPAF,   1999).Carbon   storage   was   assessedaccording    to   the   following    formula:C   stock   (t   ha  1 C)=carbon   content   (%)  bulk   density(Mg    m  3 )    layer   depth   (m)      10,000   (m 2 ha  1 ).Soil   C   stock   was   then   converted   to   CO 2  and   the   meanannual   CO 2  increase/depletion   was   evaluated.Data   reported   in   thispaper   referred   to   the   weighted   averageof    0–0.60m   layer   which   is   the   mostexplored   by   root   systems   of both   olive   trees   (even   ifoliveroots   are   able   to   go   deeper   in   thesoil)   andcover   crops.   Although   carbon   tends   to   accumulate   onthe   topsoilbecause   of    huge   organic   input(leaves,   pruning material,   etc. ),dead   roots   and   root   exudates   represent   otherimportant   sources   ofcarbon   in   the   soildeeper   layers. 2.7.    Assessment   ofCO 2  emissions CO 2  emissions   from   the   two   management   systems   weredivided   into   anthropogenic   and   natural   emissions. 2.7.1.   Calculation   of    anthropogenic   CO 2  emissions The   anthropogenic   contribution   was   calculated   asthe   sum   of CO 2  emissions   tiedto   the   use   offertilizer   units   (distributed   bytreated   urban   wastewater   and   supplemental   fertilizers),pesticides,   machines   for   farm   operations,   product   transpor-tation,   and   pruned   residues   burning.   Except   for   pruning material   burning,   CO 2  emissions   were   expressed   ascarbondioxide   equivalent   (CO 2 eq)   which   is   ameasure   used   tocompare   the   emissions   from   various   greenhouse   gases   (CH 4 ,N 2 O, etc. )   based   upon   their   global   warming    potential.   Withrespect   to   the   agricultural   chemicals   (N,   P,and   K   fertilizers,insecticides)   CO 2 eq   emissions   were   obtained   by   multiplying the   amount   of    the   active   ingredient   distributed   (kg    ha  1 )   by   theconversion   coefficients   reported   in   Lal(2004).   Machine   CO 2 eqemissions   were   assessed   bymultiplying    diesel   fuel   consump-tion   with   the   conversion   coefficient   specifically   indicated   byLal   (2004).CO 2  emissions   from   thepruning    material   pruning,   com-monly   performed   by   theolive   growers   in   the   experimentalarea,   were   considered   equal   to   the   CO 2  fixed   in   them. 2.7.2.   Calculation   of    natural   CO 2  emissions Natural   CO 2  emissions   can   be   attributed   to   soil   respiration(heterotrophic   and   autotrophic   components).Soil   respirationvalues   used   in   this   study   weretaken   from   theavailable   literature   and   adjusted   to   our   experimental   condi-tions.   Particularly,the   annual   CO 2  effluxfrom   CS   soilwasassessed   equal   to   21.00   t   ha  1 year  1 beginning    from   data   foundby   Almagro   et   al.   (2009)   for   a   rainfed   and   tilled   olive   grove(10   m      10   m)   located   in   S.E.   Spain   (average   annual   precipita-tion   of    370   mm).   The   authors   measured   CO 2  effluxes   of 824.04   and   328.86   g    C   m  2 year  1 at   beneath-   and   inter-canopylocations,   respectively.   Taking    intoaccount   the   canopyarea   of  e   n   vi   r   o   nmen   ta   ls   ci   en   c   e   &po   licy   27(   2   013)   81–   90 84  one   olive   treebelongingto   the   experimental   orchard(31.52   m 2    3.27,mean  standard   deviation),   we   referred   theCO 2  effluxes   to   the   underand   inter-canopy   zones   of    CS.Soilrespiration   ascribed   to   SS   was   equal   to   21.32   tha  1 year  1 .   Inthis   case,   we   utilized   data   indicated   byTesti   etal.(2008)   for   adrip-irrigated   young    olive   orchard   grown   nearCo´rdoba   –Spain(408   trees   ha  1 )   where   weeds   were   controlled   byherbicideswithout   tillage   operations.   In   particular,   the   authors   reportedsoil   CO 2  effluxmeasurements   taken   from   the   permanentlywet   zones   nearthe   drippers,   rangingfrom   0.08   to0.25   mgCO 2  m  2 s  1 ,   andthe   dry   soilin   the   inter-rows   alleys,ranging    from   0.05   to   0.07mgCO 2  m  2 s  1 .   Wereferred   theaverage   of    the   former   values   to   the   specific   wet   area   ofthe   SS(735.13   m 2 in   regard   to   1   ha)   and   the   latter   to   the   remainingpartof    the   experimental   plot. 3.Results 3.1.   Yield   and   olive    features Olive   trees   belonging    to   SS   were   able   to   produce   almostconstantly   every   year   with   ayield   2.3   times   higher,   on   average,than   that   harvested   from   the   CS   plants   (62.6   versus 27.0   kg    plant  1 –   mean   2001–2008)   which,   on   the   contrary,were   strongly   affected   by   analternate   bearing    behaviour(Table   1).   Similarly,   drupes   developed   on   SS   trees   showed   thebest   technological   parameters.   Particularly,   the   fresh   weightof    the   drupe   from   SS   trees   was   3.8    1.0   g    versus   2.5    0.8   gof the   CS   olive   (mean   2001–2008      standard   deviation).   Inaddition,   the   average   pulp   percentage   with   respect   to   thetotal   olive   fresh   weight   was   about   85%      4.4   and   78%      5.8   inSS   and   CS   drupes,   respectively.   The   pulp   to   stone   ratio   wasequal   to   6.1      2.4   in   SS   and   4.0    1.6   in   CS.   On   average,   about93%   of    the   fruits   taken   from   SS   fell   in   theequatorial   diameterclasses   ranging    from   > 14   mm   to    20   mm,while   in   CS   suchpercentage   was   equal   to   48%. 3.2.   Economic   aspects The   availability   of    data   for   the   experimental   8-years   periodmade   itpossible   to   evaluate   the   trend   in   economic   results   of the   two   compared   systems.Annual   TO   per   hectare,   calculated   atconstant   values(Table   2),   was   strongly   affected   by   the   extentof    crop   loadmeasured   in   the   experimental   years   (Table   1)   and   by   itscomposition   asfunction   offruit   merceological   parameters   (size,weight,   pulp   to   stone   ratio).   Particularly,   TO   ofthe   SS   wasconstantly   positive   and   greater   than   that   of    the   CS   (Table   2).   Forthis   last,the   production   in   ‘on’   years   was   characterised   by   alower   amount   oftable   olives   (less   than   50%   ofthe   annual   crop)which   usuallysprout   higher   prices   (1150   s t  1 against   400   s   t  1 for   olives   to   be   directed   atoil   production   –prices   recorded   on   themarketplace   of    Ferrandina   in   2009/2010   harvesting    campaign).In   addition,   the   low   selling    price   of    olives   used   for   oil   productiondid   not   makeharvesting    economically   worthwhile   in   ‘off’   yearwhen   the   CS   showed   no   or   very   lowyields   (Tables   1and   2).The   SS   showed   higher   PC   (from   3799   to   6010   s   ha  1 year  1 )than   CS   (from   1447   to   2978   s   ha  1 year  1 )   (Table   3).Inparticular,   the   VC   increased   more   than   theFCones,   due   tothe   intensification   ofthe   production   process   (Tables   4   and   5).The   GP   ofthe   SSwas   always   positive   and   often   higherthan   5900   s   ha  1 year  1 and   up   to   amaximum   of 12,620   s   ha  1 year  1 (Fig.1).Anomalies   were   observed   in2004   and   2006   when   the   low   crop   (Table   1)   made   possible   to just   cover   Production   Costs.   The   GP   of    the   CS   ranged   from   1615to   5240   s ha  1 year  1 (Fig.   1)   in   ‘on’   years   while   itwas   alwaysnegative   in   those   characterised   by   no   or   low   productivity(2002,   2004,   and   2006)   (Table   1).Despite   the   alternatebehaviour   and   the   lower   quality   of    yields,   the   average   GP   of  Table   1   –   Mean   yield   pertree   (  W standard   deviation)   overthe   years   in   the   examined   systems.   Asterisk   indicates   an‘off’   year. Year   System   (kg    plant  1 )Sustainable   Conventional 200164.7    16.435.2  7.7200279.5    4.10*2003   69.4    21.939.5  13.5200430.1    18.30*2005   61.7    14.544.8  15.9200623.4    5.00*2007   66.5    13.151.1  10.02008103.9    13.641.7  5.6 Table   2   –   Annual   Total   Output    (  s ha S 1 year S 1  )   calculated   for   the   examined   systems. System   Year2001   2002   200320042005   2006   2007   2008 Sustainable( s ha  1 year  1 )11,61513,69411,967519510,628402911,46318,630Conventional( s   ha  1 year  1 )   47910   321105530071335234 Table   3   –Annual   Production   Costs   (PC)   (  s   ha S 1 year S 1  ),calculated   as   the   sum   ofVariable   Costs   and   Fixed   Costs,for   the   examined   systems. Year   SystemSustainable   Conventional( s   ha  1 year  1 ) 200146411447200248731940200347561595200438421940200546611744200637991940200747711892200860102978 env   i   r   o   n   m   en   t   als   ci   ence&p   o   licy27(   2013)   81–90 85
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