Technological Approaches to Sustainable Agriculture at a Crossroads

13 Pages·2017·0.79 MB·English

sustainability
Article
Technological Approaches to Sustainable Agriculture
at a Crossroads: An Agroecological Perspective
MiguelA.Altieri1,*,ClaraI.Nicholls2andReneMontalba3
1 DepartmentofEnvironmentalScience,PolicyandManagement(ESPM),UniversityofCalifornia,
Berkeley,CA94720,USA
2 InternationalandAreaStudies,UniversityofCalifornia,Berkeley,CA94720,USA;[email protected]
3 DepartamentodeCienciasAgronomicasyRecursosNaturales,UniversidaddelaFrontera,
FranciscoSalazar,01145Temuco,Chile;[email protected]
* Correspondence:[email protected]
AcademicEditors:ManuelGonzálezdeMolinaandGloriaGuzman
Received:24November2016;Accepted:23February2017;Published:27February2017
Abstract: Mosteffortstoimproveagriculturalproductionremainfocusedonpracticesdrivenby
anintensificationagendaandnotbyanagroecologicalone. Agroecologytranscendsthereformist
notionoforganicagricultureandsustainableintensificationproponentswhocontendthatchanges
canbeachievedwithinthedominantagroindustrialsystemwithminoradjustmentsor“greening”
ofthecurrentneoliberalagriculturalmodel. Inthetechnologicalrealm,merelymodifyingpractices
toreduceinputuseisastepintherightdirectionbutdoesnotnecessarilyleadtotheredesignofa
moreselfsufficientandautonomousfarmingsystem. Atrueagroecologicaltechnologicalconversion
callsintoquestionmonocultureandthedependencyonexternalinputs. Traditionalfarmingsystems
providemodelsthatpromotebiodiversity,thrivewithoutagrochemicals,andsustainyear-round
yields. Conversionofconventionalagriculturealsorequiresmajorsocialandpoliticalchangeswhich
arebeyondthescopeofthispaper.
Keywords: agroecology;organicagriculture;conversion;transition;LatinAmerica;California
1. Introduction
InLatinAmerica,agroecologyisnotonlyascientific–technologicalproject,butapoliticalone.
Agroecologyisviewedasanappliedscienceembeddedinasocialcontext,problematizingcapitalist
relationsofproductionandallyingitselfwithagrariansocialmovements[1]. Mostagroecologistshave
embracedthecritiquesoftopdownruraldevelopmentandrecognizedandsupportedthepeasantry
intheirnewroleintheresistanceagainsttheadvancementofthecorporatefoodsystem,industrial
agricultureandneoliberalpolicies[2].
Itispreciselythispoliticaldimensionofagroecologythatisproblematicfortheapplicationand
spreadofagroecologyintheUSA,Europe,Australia,Japanandotherregionsintheindustrialized
world. Challengingtherootcausesoftheenvironmentalandsocialcrisisofindustrialagriculture
implieschallengingcapitalism. Givensuchchallenge,anaivenotionprevailsthatsocio-ecological
changescanbeachievedwithinthecurrentfoodsystemwithjustalittletweakingand“slightgreening”
oftheindustrialagriculturalmodel[3]. Usingavarietyofnames(sustainableintensification,climate
smartagriculture,diversifiedfarmingsystems,adaptivemanagement,etc.),alukewarmdefinition
ofagroecologyhasemerged,regardingitessentiallyasasetofadditionaltoolstofixtheproblems
ofindustrialfoodproduction. Inotherwords,manyresearchersseeagroecologyasawaytomake
conventional agriculture a little bit more sustainable, without challenging underlying relations of
power,northestructureoflarge-scalemonocultures[4]. Nodoubt,agroecologyisnowatacrossroads,
facingamajorstruggleoveritspossiblecooptationbythemainstreamandtobefurthersubordinated
Sustainability2017,9,349;doi:10.3390/su9030349 www.mdpi.com/journal/sustainability
Sustainability2017,9,349 2of13
toconventionalagriculturebyrevisionistacademicprojectsthateraseitshistory,strippingitofits
politicalcontentandgoals[5].
Thetechnologicalparadigmespousedbysuch“a-political”conceptionofagroecologycarriesthe
sameshortfalls. Definingagroecologysolelyasascienceandpracticeofapplyingecologicalprinciples
to the design and management of sustainable farms [6] opens the door to a variety of competing
narratives, each suggesting different pathways to supposedly reach healthier agricultural futures.
Hallmarksofwhataretermedagroecologicalfarmingpracticesincludeintegratedpestmanagement,
organicfarming,conservationagriculture,regenerativeagriculture,sustainableintensification,etc.,all
approachesbasedonpracticesthatimplyonlyminoradjustmentstotheindustrialfarmingmodel.
In this paper, we argue that what is required, is to rescue agroecology from the confines
of academia and non-governmental organizations, into the political arena of progressive social
movementsthatembraceagroecologyasapillaroffoodsovereignty,localautonomy,andcommunity
controlofland,waterandagrobiodiversity. Promotinganagriculturebasedonpracticesthatincrease
theefficiencyofinputuseorthatsubstitutebiologicallybasedinputsforagrochemicals,butthatdonot
challengethemonoculturestructure,donothavethepotentialtoleadtoamoreautonomousredesign
ofsovereignagriculturalsystems. Atrueagroecologicaltechnologicalconversioncallsintoquestion
monoculture and the dependency on external inputs. This conversion also implies socio-political
dimensionsthatarebeyondthescopeofthispaper.
2. Agroecology,OrganicFarmingandSustainableIntensification
Therearemanymanifestationsofalternativeagriculture:biodynamicagriculture,organicfarming,
permaculture,naturalfarmingandothers. Allthesemethodspromoteadiverserangeofalternative
practicesdesignedtoreducedependenceonsyntheticchemicalpesticides,fertilizers,andantibiotics,
andcutproductioncosts,whichinturndiminishadverseenvironmentalconsequencesofmodern
agriculturalproduction[7]. Oneofthesesystemsisorganicagriculturewhichispracticedinalmostall
countriesoftheworld,anditsshareofagriculturallandandfarmsisgrowing,reachingacertified
areaofmorethan30millionhectaresglobally. Organicfarmingisaproductionsystemthatsustains
agriculturalproductivitybyavoidingorlargelyexcludingsyntheticfertilizersandpesticides. Instead
organicfarmersrelyheavilyontheuseofcroprotations,covercroppingandgreenmanuring,crop
residues,animalmanures,legumes,off-farmorganicwastes,mechanicalcultivation,mineral-bearing
rocks,andaspectsofbiologicalpestcontroltomaintainsoilproductivityandtilth,tosupplyplant
nutrients,andtocontrolinsectpests,weeds,anddiseases[8].
Pushed by market forces that privilege specialization, many organic farmers have no choice
but to replace practices such as rotations, cover cropping, etc. with a set of energy and capital
intensiveorganic“technologypackages”andinputsubstitutions,makingtheiroperationsdependent
andintensive[9]. Conversionhasbeenconceptualizedasatransitionalprocesswiththreemarked:
(1)Increasedefficiencyofinputusethroughintegratedpestmanagementorintegratedsoilfertility
management;(2)Inputsubstitutionorsubstitutionofenvironmentallybenigninputs;and(3)System
redesign-diversification with an optimal crop/animal diversified assemblage, which encourages
synergismssothattheagroecosystemmaysponsoritsownfunction[10]. Manyofthepracticesthat
arecurrentlybeingpromotedassustainablefallincategories1and2. Bothofthesestagesreduce
environmentalimpactsastheydecreaseagrochemicalinputuse. Solelyincreasingtheefficiencyof
inputuseorsubstitutingbiologicallybasedinputsforagrochemicals,butleavethemonocultureintact,
dolittletomovefarmerstowardtheproductiveredesignofagriculturalsystems.
Manyofthe“alternativeinputs”usedinorganicfarminghavebecomecommodified,therefore
farmerscontinuetobedependentoninputsuppliers. InCalifornia,manyorganicfarmerscultivating
grapes and strawberries apply between 12 and 18 different types of biological inputs per season
enhancingproductioncosts. Manyproductsusedforonepurposeaffectotheraspectsofthesystem.
Sulfurusedtocontrolfoliardiseasesofgrapes,canalsowipeoutpopulationsofAnagrusparasitic
wasps,keyregulatorsofleafhopperpests. Thusfarmersbecometrappedinan“organictreadmill”[11].
Sustainability2017,9,349 3of13
Manyagroecologistsarguethatimprovementsinefficiencyofinputuseandinputsubstitutionmust
givewaytofarmingsystemredesignbasedonanewsetofecologicalrelationships,whichentailsbasing
conversiononprinciplesofagroecology[12]. Thecoreprinciplesofagroecologyincluderecycling
nutrients and energy on the farm, rather than introducing external inputs; enhancing soil organic
matterandsoilbiologicalactivity;diversifyingplantspeciesandgeneticresourcesinagroecosystems
overtimeandspace;integratingcropsandlivestockandoptimizinginteractionsandproductivityof
thetotalfarmingsystem,ratherthantheyieldsofindividualspecies[13,14].
RecentlyFAO[15]alongwithotherinternationalorganizations(i.e.,CGIAR)haveembraceda
versionofagreocology,regardedasanoptionthatcanbepracticedalongwithotherapproachessuchas
transgeniccrops,conservationfarming,microdosingoffertilizersandherbicides,andintegratedpest
management. Theyproposeadjustingtheecologicalinefficienciesofindustrialagriculturethrough
“sustainableintensification”,e.g.,byincreasingefficiencyofwaterandfertilizeruse,andconfronting
climatechangebydeploying“climate-smart”geneticvarieties. Ofcoursethisvisionrenderstheterm
agroecologymeaningless,likesustainableagriculture,aconceptdevoidofmeaning,anddivorcedfrom
therealityoffarmers,thepoliticsoffoodandoftheenvironment. Infact,thesesuperficialtechnical
adjustmentsareideologicallybuttressedbyintellectualprojectstoreframeandredefineagroecology
bystrippingitofitspoliticalandsocialcontentandpromotethewrongnotionthatagroecological
methodscanco-existalongsidetheaggressiveexpansionofindustrialagriculture,transgeniccrops
andagrofuels[16]. Agroecologydoesnotneedtobecombinedwithotherapproaches. Withoutthe
needofhybridsandexternalagrochemicalinputs,ithasconsistentlyprovencapableofsustainably
increasingproductivityandhasfargreaterpotentialforfightinghunger,particularlyduringeconomic
andclimaticallyuncertaintimes,whichinmanyareasarebecomingthenorm.
3. TraditionalAgricultureasSustainabilityandResiliencyModels
In the current realm of commercial agriculture, it is difficult to find agricultural systems that
promotebiodiversity,thrivewithoutagrochemicals,andsustainyear-roundyields. Forthisreason,
in their search for new and promising models, agroecologists have turned their attention to the
studyoftraditionalagriculture. Suchcomplexfarmingsystems,adaptedtolocalconditions,have
helpedsmallfarmerstosustainablymanageharshenvironmentsandtomeettheirsubsistenceneeds,
withoutdependingonmechanization,chemicalfertilizers,pesticidesorothertechnologiesofmodern
agricultural science [17]. Guided by an intricate knowledge of nature, traditional farmers have
nurtured biologically and genetically diverse smallholder farms with a robustness and a built-in
resiliencenecessarytoadjusttorapidlychangingclimates,pests,anddiseases,andmorerecentlyto
globalization,technologicalpenetration,andothermoderntrends[18].
A salient feature of traditional farming systems is its high level of biodiversity deployed in
theformofpolycultures,agroforestryandothercomplexfarmingsystems,inwhichtheecological
interactionsamongplant,animalandsoilcomponentspromotekeyprocessessuchasnutrientcycling,
pestregulationandproductivity. Guidedbyanacuteobservationofnature,manytraditionalfarmers
haveintuitivelymimickedthestructureofnaturalsystemswiththeircroppingarrangements[19].
Examples of such bio mimicry abound and below we describe two striking examples from which
principlescanbederivedtodesignmodernagroecosystems.
3.1. TheRice-Fish-DuckSystemsinChina
ThemainspeciespresentinmanyChinesetraditionalricepaddiesincludefish,ducks,weeds,
plankton,photosyntheticbacteria,aquaticinsects,benthos,ricepests,watermice,watersnakes,birds,
andothersoilandwatermicrobes. Inaddition,farmersplantuptotendifferentspeciesofindigenous
vegetablesinthefieldbordersoftheterracefields,wherealsoatleast62forestspeciesthrive;21ofthese
usedasfoodand53formedicinalandherbalpurposes[20]. Thesericebasedfarmingsystemssupport
a variety of beneficial interactions: the various species of fish (Tilapia nilotica and Cyprinus carpio)
consumeinsectpests(mainlyleafhoppersandleafrollers)thatattackthericeplantaswellasweeds
SSuussttaaiinnaabbiilliittyy 22001177,, 99,, 334499 44 ooff 1133
the rice plant as well as weeds that choke rice plants and rice leaves infected by sheath blight disease
that choke rice plants and rice leaves infected by sheath blight disease thus reducing the need for
thus reducing the need for pesticides. These systems exhibit a lower incidence of insect pests and
pesticides. Thesesystemsexhibitalowerincidenceofinsectpestsandplantdiseaseswhencompared
plant diseases when compared to monoculture rice farming [21]. Further, the fish oxygenate the
tomonoculturericefarming[21]. Further,thefishoxygenatethewaterandmovethenutrientsthereby
water and move the nutrients thereby benefiting the rice. Azolla species proliferate fixing nitrogen
benefitingtherice. Azollaspeciesproliferatefixingnitrogen(243–402kg/ha)someofwhich(17%–29%)
(243–402 kg/ha) some of which (17%–29%) is used by the rice [22]. The ducks consume the Azolla
isusedbytherice[22]. TheducksconsumetheAzollabeforeitcoversthewholesurfaceandtriggers
before it covers the whole surface and triggers eutrophication, in addition to consuming snails and
eutrophication,inadditiontoconsumingsnailsandweeds. Byconsumingbiomass,thefishandducks
weeds. By consuming biomass, the fish and ducks reduce the methane emissions otherwise
reducethemethaneemissionsotherwiseproducedbydecomposingvegetationbyupto30percent,as
produced by decomposing vegetation by up to 30 percent, as compared to conventional farming.
comparedtoconventionalfarming. Clearly,thecomplexanddiversefoodwebsofmicrobes,insects,
Clearly, the complex and diverse food webs of microbes, insects, predators and associated crops
predatorsandassociatedcropsplantspromoteanumberofecologicalaswellsocialandeconomic
plants promote a number of ecological as well social and economic services, beneficial to the local
services,beneficialtothelocalruralcommunities(Figure1).
rural communities (Figure 1).

Figure 1. Interactions among different components in Chinese rice–fish–duck agricultural systems
Figure1.InteractionsamongdifferentcomponentsinChineserice–fish–duckagriculturalsystems[20].
[20].
3.2. TheMilpa
3.2. The Milpa
Intercropping is a form a bio mimicry which is widely practiced in Latin America, Asia, and
Intercropping is a form a bio mimicry which is widely practiced in Latin America, Asia, and
Africabysmallholdersasameansofincreasingcropproductionperunitlandarea,withlimitedcapital
Africa by smallholders as a means of increasing crop production per unit land area, with limited
investmentandminimalriskoftotalcropfailure[23]. Inthesetraditionalmultiplecroppingsystems,
capital investment and minimal risk of total crop failure [23]. In these traditional multiple cropping
productivityintermsofharvestableproductsperunitareacanrangefrom20%to60%higherthan
systems, productivity in terms of harvestable products per unit area can range from 20% to 60%
undersolecroppingwiththesamelevelofmanagement[24]. Themechanismsthatresultinhigher
higher than under sole cropping with the same level of management [24]. The mechanisms that
productivityindiverseagroecosystemsareembeddedintheprocessoffacilitation. Facilitationoccurs
result in higher productivity in diverse agroecosystems are embedded in the process of facilitation.
whenonecropmodifiestheenvironmentinawaythatbenefitsasecondcrop,forexamplebylowering
Facilitation occurs when one crop modifies the environment in a way that benefits a second crop, for
thepopulationofacriticalherbivore,orbyreleasingnutrientsthatcanbetakenupbythesecond
example by lowering the population of a critical herbivore, or by releasing nutrients that can be
crop[25]. Pestandpathogenincidenceisgenerallylowerinintercropsduetoassociationalresistance
taken up by the second crop [25]. Pest and pathogen incidence is generally lower in intercrops due to
effects[26]andhighertotalresourceuseefficiencyresultswhengrowingtogethercropswithdifferent
associational resistance effects [26] and higher total resource use efficiency results when growing
root systems and leaf morphologies. Usually a combination of two contrasting species, usually a
together crops with different root systems and leaf morphologies. Usually a combination of two
legumeandacereal,leadstogreateroverallbiologicalproductivitythaneachspeciesgrownseparately
contrasting species, usually a legume and a cereal, leads to greater overall biological productivity
becausethemixturecanuseresourcesmoreeffectivelythanseparatemonocultures[27]. Intercropping
than each species grown separately because the mixture can use resources more effectively than
is an effective agroecological strategy of introducing more biodiversity into agroecosystems and
separate monocultures [27]. Intercropping is an effective agroecological strategy of introducing more
increasedcropdiversityusuallyincreasesthenumberofecosystemservicesprovided. Higherspecies
biodiversity into agroecosystems and increased crop diversity usually increases the number of
ecosystem services provided. Higher species richness of planned and associated biodiversity
Sustainability2017,9,349 5of13
Sustainability 2017, 9, 349 5 of 13
rimichpnroevsseso fnpultarinennet dcyacnldinags saoncdia tseodil bfieordtiilviteyr,s iltiymiitm npurotrvieenstn luetarciehnintgc ylcolsisnegs,a nreddusoceils fethrtei lintye,glaitmiviet
nimutpraiecntst olef apcehsitnsg, dliossesaesse,sr aenddu cweseetdhes annedg aetnivheanimceps aocvtseroafllp reesstisli,ednicsee aosf etshea ncrdopwpeiendgs saynsdtemen (hFaingucerse
o2v) e[2ra8l]l. resilienceofthecroppingsystem(Figure2)[28].

FFiigguurree 22. .SocioS-Eoccoiolo-Egcicoallo goiuctaclomoeust cfroomme sintfrreocmroppinintrge csryosptepminsg dessyigstneemd sbadseedsi gonne adgrobeacsoeldogiocanl
apgrrinoceicpolleosg. icalprinciples.
Among the most prevalent intercropping systems is the “milpa”, a polyculture originated and
Amongthemostprevalentintercroppingsystemsisthe“milpa”,apolycultureoriginatedand
still practiced in Mexico and the rest of Mesoamerica. In this system maize, common beans and
stillpracticedinMexicoandtherestofMesoamerica. Inthissystemmaize,commonbeansandsquash
squash are typically grown in association, sometimes along with tomatoes, multiple varieties of
aretypicallygrowninassociation,sometimesalongwithtomatoes,multiplevarietiesofchiliesand
chilies and semi-domesticated herbs (quelites). In this system, beans fix nitrogen which benefit maize,
semi-domesticatedherbs(quelites). Inthissystem,beansfixnitrogenwhichbenefitmaize,butalso
but also harbor beneficial insects that control maize pests. Squash plants suppress weeds and protect
harborbeneficialinsectsthatcontrolmaizepests. Squashplantssuppressweedsandprotectagainst
against erosion by quickly covering the soil. Maize provides support to climbing beans and shade
erosionbyquicklycoveringthesoil. Maizeprovidessupporttoclimbingbeansandshadeforbeans
for beans creating a microclimate unfavorable to certain insect pests while also preserving moisture.
creatingamicroclimateunfavorabletocertaininsectpestswhilealsopreservingmoisture. Inaddition,
In addition, maize forms a physical barrier against certain diseases by blocking the dissemination of
maizeformsaphysicalbarrieragainstcertaindiseasesbyblockingthedisseminationofspores[23].
spores [23]. All these interactions favor productivity leading to over yielding; the crop mixture
Alltheseinteractionsfavorproductivityleadingtooveryielding;thecropmixtureyieldsmorethan
yields more than any monoculture of the component species despite their low use of chemical
anymonocultureofthecomponentspeciesdespitetheirlowuseofchemicalinputs. Moststudies
inputs. Most studies reveal land equivalent ratios (LER) values for maize/bean polycultures higher
reveallandequivalentratios(LER)valuesformaize/beanpolycultureshigherthan1.5[24]. InMexico,
than 1.5 [24]. In Mexico, 1.73 ha of land has to be planted with monoculture maize to produce as
1.73haoflandhastobeplantedwithmonoculturemaizetoproduceasmuchfoodasonehectare
much food as one hectare planted with the traditional milpa (mixture of maize, beans and squash).
plantedwiththetraditionalmilpa(mixtureofmaize,beansandsquash).
Most milpa farmers destine maize cultivation to obtain grain for human consumption and seeds
for the following agricultural cycle, as well as straw for direct consumption of households’ animals.
Our studies in Tlaxcala showed that a typical milpa parcel produces on average 1200 kg of maize
grain per hectare [29]. Daily consumption of maize is on average 3 kg per household, thus maize
Sustainability2017,9,349 6of13
Mostmilpafarmersdestinemaizecultivationtoobtaingrainforhumanconsumptionandseeds
forthefollowingagriculturalcycle,aswellasstrawfordirectconsumptionofhouseholds’animals.
OurstudiesinTlaxcalashowedthatatypicalmilpaparcelproducesonaverage1200kgofmaizegrain
perhectare[29]. Dailyconsumptionofmaizeisonaverage3kgperhousehold,thusmaizeproduction
(without accounting for the yields of beans, squash and other crops and quelites (which amount
toanadditionaltotalediblebiomassofapproximately1.5tons)coversthe1-tonannualhousehold
maize requirement, plus 20–25 kg/ha of seeds needed for sowing the next season. In addition, a
maize–squash–beanpolyculturecanproduceupto4t/haofdrymatterthatcanbeusedasfodder
(strawfromtenmaizeplantsareusedtofeedoneortwoanimalsperday),orplowedintothesoilas
greenmanure,comparedwith2t/hainamaizemonoculture.
4. TowardsaRadicalRe-DesignofAgroecosystems
Studieselucidatingtheunderpinningsoftraditionalfarmingsystemssuggestthatinorderto
incorporateanecologicalrationale,modernagroecosystemsrequiresystemicchange. However,new
redesignedfarmingsystemswillnotemergefromsimplyimplementingasetofpractices(rotations,
composting,covercropping,etc.),whichtendtoaddresscomponentsinisolation,focusingonthe
optimizationofonecomponent(soilfertility,plantnutrition,cropgrowth,etc.) failingtoexploitthe
propertiesthatemergethroughtheinteractionofthevariousfarmcomponents.Inputsubstitutionthus
becomesprimarilyreactive,shiftingeffortstosolvingproblemsastheyarise,amelioratingsymptoms
ratherthandiscoveringrootcauses[30].
Insteadoffocusingononeparticularcomponentoftheagroecosystem,agroecologyemphasizes
the interrelatedness of all agroecosystem components and the complex dynamics of ecological
processes. Thus agroecology is an alternative approach that goes beyond the use of alternative
inputstodevelopintegratedagroecosystemswithminimaldependenceonexternal,off-farminputs.
The emphasis is on the design of complex agricultural systems (similar to the rice–fish–duck and
milpasystemsdescribedabove)inwhichecologicalinteractionsandsynergismsbetweenbiological
componentsreplaceinputstoprovidethemechanismsforsponsoringsoilfertility,productivity,and
cropprotection[31].
Agroecologicalsystemredesignconsistsintheestablishmentofanecologicalinfrastructurethat
encourages ecological interactions through restoration of agricultural biodiversity at the field and
landscapelevel. Asinthecaseoftherice–fish–duckandmilpasystems,welldesignedbiodiverse
agroecosystemsexhibitanumberofsynergieswhichinturnleadtoenhancedsoilfertility,nutrient
cyclingandretention,waterstorage,pest/diseaseregulation,pollination,andotheressentialecosystem
services. The production, resource conserving and socio-economic benefits of integrated farms
designedbasedonagroecologicalprincipleshavebeenwidelydescribedintheliteraturefeaturing
examplesfromLatinAmerica,AsiaandAfrica(Table1)[32].
Theassociatedcost(labor,resources,andmoney)toestablishtheecologicalinfrastructureofan
integratedfarm(soilconservationworks,livingfences,croprotations,insecthabitats,etc.) duringthe
redesignphasetendtobehighinthefirst3–5years[33]. Oncetherotationandothervegetational
designs(covercrops,polycultures,fieldborders,etc.) startlendingecologicalservicestothefarmby
settinginmotionkeyecologicalprocesses,theneedforexternalinputsandthusmaintenancecostsstart
decreasingasthefunctionalbiodiversityofthefarmsponsorsecologicalfunctions(nutrientcycling,
pestregulation,etc.),thusfamersdonothavetoweedorfertilizetheirfieldsasoften. Afteryears
ofconversion,theneedforexternalinputsdecreaseasdesignedbiodiversefarmsstartsponsoring
theirownfunction[30]. Thetransitionisfromcapital–inputintensivetoaprocess-basedagriculture
(Figure3).
Sustainability2017,9,349 7of13
Sustainability 2017, 9, 349 7 of 13
oriTgainbalete1s. fMroamin leoncvairl osnomurecnetas l(,bsioocmialaasns,d bfiooogdass efcruormity biimodpiagcetsstoofrvsa, rainouimsaagl rtoraeccotiloongi,c haulimniatina tliavbesor,
etci.m) plementedinLatinAmerica[31,33].
Social cohesion: flourishing of local social organizations; collective efforts for restoration and
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withnativespecies
negative external influences and to fight for rights.
Waterconservation:harvested-collectedwatersufficientforfamilyconsumptionandsubsistencecropplots;protection
Economic viability: local markets; solidarious networks with consumers, low dependency of
ofriparianforests;massiveimplementationofwaterharvestingtechniques;soilorganicmatterenrichmenttoenhance
ewxatteerrnhaolld iinnpgucatps;a clietsys debt; agroecotourism initiatives controlled by the community;
cSoomilmconesrecrivaaltiizoant:iroenst oorfa tpiornodofudcetgsr awdeitdhs ociulsl;teurroasilo indceonnttriotylv. iaimplementationofseveralsoilconservation
practices(terracing,contourfarming,mulching,etc.)
RecoTvheery aasnsdoccoiantseedrv actoiosnt (olfanbaotirv, eregesromuprlcaessm, :arnecdo vmeroynoefyth)o tuos aensdtsaboflilsanhd thraec eescaonldolgoiccaallly iandfarpatsetdrusecetdusrvei aof an
onfarm-conservationprograms,seedfairs,networksofseedsaversandparticipatoryplantbreedingprojects.
integrated farm (soil conservation works, living fences, crop rotations, insect habitats, etc.) during
thAe grreicdueltsuigranl pprhodauscet itoenn:dim tpol ebmee hntiagthio nino fthinete fgirrastte d3–fa5r myesaferast u[3ri3n]g. rOotnatcioen tsh,ep orloyctualttiuornes aanndd aontihmearl ivneteggeratatitoino,nal
producingatleast25%moreperunitlandthanconventionalmonoculturefarms.Morethan70%oftheinputsusedin
designs (cover crops, polycultures, field borders, etc.) start lending ecological services to the farm by
thesefarmsarelocal,enhancingproductiveautonomy
setting in motion key ecological processes, the need for external inputs and thus maintenance costs
Foodself-sufficiency:Atleast60%ofthebasicfoodconsumedbythefamilyorcommunityareproducedlocally
start decreasing as the functional biodiversity of the farm sponsors ecological functions (nutrient
Energyself-sufficiency:Atleast60%oftheenergyrequiredforfoodproductionandcookingoriginatesfromlocal
cyscoluinrcges, (pbeiosmt arsesg,ubiloagtaisofnro, metcb.io),d tigheustso rfsa,maneimrsa ldtora cntoiotn h,hauvmea tnol awboere,det co.)r fertilize their fields as often. After
yeSaorcsia locfo hceosniovne:rflsoiuornis,h itnhgeo fnloeceadls ofcoiarl oerxgatenriznaatilo nisn;pcoulltesc tidveecerffeoartssef oarsre sdtoersaitgionneadn dbpiroodduivcteiornsep ufrapromsess; start
speomnpsoowreinrmge tnhteofirw oowmenn faunndcytoioutnh ;[h3i0g]h.e Trshoec iatrlaconhseistiioonnt oisr efsriostmne cgaatpivietaelx–teinrnpaulitn iflnuteenncessivaned toto afi gphrtofocresrisg-hbtsa.sed
agErciocnuolmtuicrev i(aFbiigliutyr:el o3c)a.l markets;solidariousnetworkswithconsumers,lowdependencyofexternalinputs;lessdebt;
agroecotourisminitiativescontrolledbythecommunity;commercializationofproductswithculturalidentity.

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As shown in the Milpa system, legumes intercropped with cereals is a key diversification
strategy, not only because of their provision of nitrogen, but also because the mixtures enhance soil
Sustainability2017,9,349 8of13
AsshownintheMilpasystem,legumesintercroppedwithcerealsisakeydiversificationstrategy,
not only because of their provision of nitrogen, but also because the mixtures enhance soil cover,
smotherweedsandincreasenutrients(e.g.,potassium,calciumandmagnesium)inthesoilthrough
theadditionofbiomassandresiduestothesoil.Suchintercroppingsystemsalsoincreasesoilmicrobial
diversitysuchasvesiculararbuscularmycorrhizae(VAM)fungiwhichfacilitatephosphoroustransfer
tothecropsandenhancecropswateruseefficiency[36]. Inthecaseofadverseweatherconditions,
such as a delay in the onset of rains and/or failure of rains for a few days, weeks or during the
croppingperiod,anintercroppingsystemprovidestheadvantagethatatleastonecropwillsurvive
togiveeconomicyields,therebyservingasthenecessaryinsuranceagainstunpredictableweather.
Polyculturesexhibitgreateryieldstabilityandlowerproductivitydeclinesduringadroughtthan
monocultures. Thiswaswelldemonstratedbyresearchers[37]whoexaminedtheeffectsofdrought
onpolyculturesbymanipulatingwaterstressonintercropsofsorghum(Sorghumbicolor)andpeanut
(Arachisspp.),millet(Panicumspp.)andpeanut,andsorghumandmillet.Alltheintercropsconsistently
providedgreateryieldsatfivelevelsofmoistureavailability,rangingfrom297to584mmofwater
applied over the cropping season. Interestingly, the rate of over-yielding actually increased with
waterstress,suchthattherelativedifferencesinproductivitybetweenmonoculturesandpolycultures
becamemoreaccentuatedasstressincreased.
No-till row crop production is also promising, given its soil conservation and improvement
potential,butitishighlydependentonherbicides. However,therearesomeorganicfarmerswho
practice it without synthetic herbicides. A breakthrough occurred with the discovery that certain
winterannualcovercrops,notablycerealryeandhairyvetch,canbekilledbymowingatasufficiently
latestageintheirdevelopmentandcuttingclosetotheground. Theseplantsgenerallydonotre-grow
significantly,andtheclippingsformaninsitumulchthroughwhichvegetablescanbetransplanted
with no or minimal tillage. The mulch hinders weed seed germination and seedling emergence,
often for several weeks. As they decompose, many cover crop residues can release allelopathic
compoundsthatmaysuppressweedgrowth[38]bymeansofphytotoxicsubstancesthatarepassively
liberated through decomposition of plant residues. There are several green manure species that
haveaphytotoxiceffectwhichisusuallysufficienttodelaytheonsetofweedgrowthuntilafterthe
crop’sminimumweed-freeperiod. Thismakespost-plantcultivation,herbicidesorhandweeding
unnecessary,yetexhibitsacceptablecropyields[39]. Tomatoesandsomelate-springbrassicaplantings
performespeciallywell,andsomelarge-seededcropssuchasmaizeandbeanscanbesuccessfully
direct-sownintocovercropresidues. Notonlycancovercropsplantedinno-tillfieldsfixnitrogen
in the short term; they can also reduce soil erosion and mitigate the effects of drought in the long
term,asthemulchconservessoilmoisture. Covercropsbuildverticalsoilstructureastheypromote
deepmacroporesinthesoil,whichallowmorewatertopenetrateduringthewintermonthsandthus
improvesoilwaterstorage.
Experimentalresultsaswellasfarmers’observationsinsouthernBrazilsuggestthatcovercrops
canenhanceweedsuppressionandhencecropproductivitypossiblythroughallelopathyandviaa
hostofeffectsonsoilqualityandfertilityandsoilmoisture[40]. Resultsfromfieldtrialsindicatethat
thebestcovercropmixturesshouldincludeasignificantproportionofrye,vetch,andfodderradish,
asmixtureswiththeseplantspecies:
• producelargebiomass,atleastfourtonsofabovegrounddrymatterperhectare;
• arereadilykilledbyrollingformingathickmulchsufficienttoprovideeffectiveweedcontrolin
thesubsequentvegetablecrop;
• donotsuppressthevegetableorgraincropthroughchemical(allelopathic)ormicrobialeffects
(i.e.,Nimmobilization);and
• increasetheproportionofvetchinthemixturesdecreasestheC/Nratio,whichgivesagradual
releaseofplantavailableN.
Sustainability2017,9,349 9of13
4.2. RedesigningModernVineyards
Cover crops are often planted in between vineyard rows to reduce soil erosion, increase soil
fertility,improvesoilstructureandenhancebiologicalpestsuppression. Rootsofbothgrapevines
andcovercropsformmutualisticsymbioseswitharbuscularmycorrhizal(AM)fungi,andmaybe
interconnectedbyAMhyphae. StudieshaveshownevidenceofAMfungi-mediated15Ntransferfrom
covercropstograpevines5and10daysafterlabeling. Ntransferwassignificantlygreaterfromgrass
covercroptothegrapevinethanfromthelegumetothegrapevine. Possiblereasonsforthedifferences
betweenthetwocovercropsincludelowerNenrichmentinlegumeroots,higherbiomassofgrass
roots,and/ordifferencesinAMfungalcommunitycomposition. Sincethefungicanassociatewitha
widerangeofplants,certaincovercropscan,therefore,beanimportantreservoirorsourceofthese
fungiforyounggrapevineroots[41].
Becausemostfarmerseithermoworploughundercovercropsinthelatespring,organicvineyards
becomevirtualmonocultureswithoutfloraldiversityinearlysummer. Itisimportanttomaintain
a green cover during the entire growing season in order to provide habitat and alternate food for
naturalenemiesofinsectpests. Anapproachtoachievethisistosowsummercovercropsthatbloom
earlyandthroughouttheseason,thusprovidingahighlyconsistent,abundantandwell-dispersed
alternativefoodsource, aswellasmicrohabitats, foradiversecommunityofnaturalenemies[42].
Suchfoodsupplydecouplespredatorsandparasitoidsfromastrictdependenceongrapeherbivores,
allowinganearlybuildupofnaturalenemiesinthesystem,whichhelpsinkeepingpestpopulations
atacceptablelevels.
MaintainingfloraldiversitythroughoutthegrowingseasoninnorthernCaliforniavineyardsin
theformofsummercovercropsofbuckwheatandsunflower,reducedsubstantiallytheabundanceof
grapeleafhoppersandthrips,whiletheabundanceofassociatednaturalenemiesincreased. Intwo
consecutiveyears,vineyardsystemswithfloweringcovercropswerecharacterizedbylowerdensities
ofleafhoppernymphsandadults. Thripsalsoexhibitedreduceddensitiesinvineyardswithcover
cropsinbothseasons. Duringbothyears,generalpredatorpopulationsonthevineswerehigherin
thecover-croppedsectionsthaninthemonocultures. Generally,thepopulationswerelowearlyinthe
seasonandincreasedaspreybecamemorenumerousastheseasonprogressed. Dominantpredators
includedspiders,Nabissp.,Oriussp.,Geocorissp.,Coccinellidae,andChrysoperlasp.
Theabovestudiessuggestafewguidelineswhichneedtobeconsideredwhenimplementing
habitatmanagementstrategiestoenhancebiologicalpestcontrolinvineyards[43]:
• Selectthemostappropriateplantspecies.
• Determinethemostbeneficialspatialandtemporalarrangementofsuchplants,withinand/or
aroundthefields.
• Considerthespatialscaleatwhichthehabitatenhancementoperates(e.g.,fieldorlandscapelevel).
• Understandthepredator–parasitoidbehavioralmechanismsinfluencedbythehabitatmanipulation.
• Anticipatepotentialconflictsthatmayemergewhenaddingnewplantstotheagroecosystem.
• Developwaysinwhichtheaddedplantsdonotupsetotheragronomicmanagementpractices,
andselectplantsthathavemultipleeffects,suchasimprovingpestregulation,while,atthesame
time,contributingtosoilfertilityandweedsuppression.
5. Conclusions
Wehaveemphasizedthatmerelymodifyingpracticestoreduceinputuseisastepintheright
direction but does not necessarily lead to the redesign of a more self sufficient and autonomous
farmingsystem. Diversificationtobreakthemonocultureisakeyagroecologicalprincipletoredesign
farms. However,diversifyingfarmspersedoesnotnecessarilymeanthattheyarebeingmanaged
agroecologically, if the collection of crops/animals chosen do not interact biologically to enhance
agroecosystemfunction,asinthecaseoftheChineserice–fish–ducksystems. Manyorganicfarmsare
diversifiedtorespondtothevarietyofmarketdemands,butagroecologicallythefarmsdonotwork,
Sustainability2017,9,349 10of13
asthecropsdonotecologicallycomplementeachotherthereforefarmersstillneedexternalinputs
(althoughorganic).
Studiesofsmallholderfarmingsystemsinthetropicsshowthatacrossgeographies,biophysical
andsocio-economicconditionsthereisabroadrangeofbiodiversefarmingsystems(intercropping,
agroforestry, crop livestock integrated systems, etc.) which sustain a series of ecosystem services
such as pest regulation, enhanced productivity (LER), resiliency to climatic extremes, soil health,
waterconservation,etc.[19]. However,ecosystemservicesbundlesarenotsustainedbyjustadding
companion species at random, most associations have been tested by farmers for decades if not
centuriesandfarmersmaintainedthembecausesuchsystemsstrikeabalancebetweenfarm-level
productivity, resilience, agroecosystem health and livelihoods [32]. A community of organisms in
an agroecosystem becomes more complex when a larger number of different kinds of plants are
included,leadingtomoreinteractionsamongarthropodsandmicroorganisms,componentsofabove
andbelowgroundfoodwebs. Asdiversityincreases,sodoopportunitiesforcoexistenceandbeneficial
interferencebetweenspeciesthatcanenhanceagroecosystemsustainability.Diversesystemsencourage
complexfoodwebs,whichentailmorepotentialconnectionsandinteractionsamongmembers,creating
manyalternativepathsforenergyandmaterialflow[25]. Forthisreason,amorecomplexcommunity
exhibits more stable production and fewer fluctuations in the numbers of undesirable organisms.
Byenhancingfunctionalbiodiversity,amajorgoaloftheredesignprocessisachieved: strengthening
theweakecologicalfunctionsintheagroecosystem,allowingfarmerstograduallyeliminateinputs
altogetherbyrelyinginsteadonecosystemfunctions[44].
Newdesignsofmodernagroecosystemswillrequiresystemicchangeguidedbytheapplication
ofalreadywelldefinedagroecologicalprinciples(Table2). Theseprinciplescanbeappliedbyway
ofvariouspracticesandstrategies(Table3), eachhavingdifferenteffectsonproductivity, stability
andresiliencywithinthefarmsystem. Oneofthekeyprinciplesisdiversificationwhichoccursin
manyformsatthefield(varietymixtures,rotations,polycultures,agroforestry,andcrop–livestock
integration)andatthelandscapelevel(hedgerows,corridors,etc.),givingfarmersawidevarietyof
options andcombinations for theimplementation of thisstrategy. Emergentecological properties
developindiversifiedagroecosystemsthatallowthesystemtofunctioninwaysthatmaintainsoil
fertility, crop production, and pest regulation. Most of these systems optimize the application of
agroecologicalprinciplesthusincreasingagroecosystemfunctionaldiversityasthefoundationforsoil
quality,planthealth,cropproductivityandsystemresilience[29].
Table2.Agroecologicalprinciplesforthedesignofbiodiverse,energyefficient,resource-conserving
andresilientfarmingsystems[13,14].
Enhancetherecyclingofbiomass,withaviewtooptimizingorganicmatterdecompositionand
1.
nutrientcyclingovertime.
Strengthenthe“immunesystem”ofagriculturalsystemsthroughenhancementoffunctional
2.
biodiversity—naturalenemies,antagonists,etc.,bycreatingappropriatehabitats.
Providethemostfavorablesoilconditionsforplantgrowth,particularlybymanagingorganic
3.
matterandbyenhancingsoilbiologicalactivity.
Minimizelossesofenergy,water,nutrientsandgeneticresourcesbyenhancingconservationand
4.
regenerationofsoilandwaterresourcesandagrobiodiversity.
Diversifyspeciesandgeneticresourcesintheagroecosystemovertimeandspaceatthefieldand
5.
landscapelevel.
Enhancebeneficialbiologicalinteractionsandsynergiesamongthecomponentsof
6.
agrobiodiversity,therebypromotingkeyecologicalprocessesandservices.