REVIEWARTICLE

Conservation agriculture cropping systems in temperateand tropical conditions, performances and impacts. A review

Eric Scopel & Bernard Triomphe & François Affholder &

Fernando Antonio Macena Da Silva & Marc Corbeels &

José Humberto Valadares Xavier & Rabah Lahmar &

Sylvie Recous & Martial Bernoux & Eric Blanchart &Ieda de Carvalho Mendes & Stéphane De Tourdonnet

Accepted: 28 June 2012# INRA and Springer-Verlag, France 2012

Abstract Nowadays, in a context of climate change, eco-nomical uncertainties and social pressure to mitigate agricul-ture externalities, farmers have to adopt new cropping systemsto achieve a sustainable and cost-effective grain production.Conservation agriculture consists of a range of cropping sys-tems based on a combination of three main principles: (1) soiltillage reduction, (2) soil protection by organic residues and(3) diversification in crop rotation. Conservation agriculturehas been promoted as a way to reduce production costs, soilerosion and soil fertility degradation under both tropical andtemperate conditions. Conservation agriculture-based crop-ping systems have diffused widely under Brazilian large-scalefarms’ conditions and more recently in Europe in the contextof medium-size mechanized farms. Their diffusion, however,is still limited under small-scale non-mechanized farms’ con-ditions of tropical countries. To assess the advantages andlimits of such new cropping systems, this article compares

experiences with conservation agriculture from the tropicalCerrado region of Brazil and from temperate conditions ofEurope. It focusses on agronomic performances, environmen-tal impacts and economical results. Conservation agriculturesystems appear to be interesting options to achieve sustainableand intensive crop production under different agroecologicalenvironments because they use efficiently available resourcesand maintain soil fertility. However, this mostly results fromthe permanent presence of an organic mulch on the soilsurface and the incorporation of cover crops in the rotations.Such modifications require a significant reorganization of theproduction process at farm level, and when facing technical orsocioeconomic constraints, most farmers usually opt for ap-plying only partially the three main principles of conservationagriculture. Investigating more fully the consequences of suchpartial implementation of conservation agriculture principleson its actual efficiency and assessing the most efficient

E. Scopel (*) : F. Affholder :M. Corbeels : R. LahmarCIRAD UPR SCA,F-34398 Montpellier, Francee-mail: eric.scopel@cirad.fr

B. TriompheCIRAD, UMR Innovation,F-34398 Montpellier, France

F. A. M. Da Silva : J. H. V. Xavier : I. de Carvalho MendesEmbrapa Cerrados,PO Box 08223, Planaltina 73310-970( Distrito Federal, Brazil

F. A. M. Da Silvae-mail: fernando.macena@embrapa.br

J. H. V. Xaviere-mail: jose-humberto.xavier@embrapa.br

I. de Carvalho Mendese-mail: ieda.mendes@embrapa.br

S. RecousINRA, UMR614 FARE,2 Esplanade Roland Garros,51100 Reims, France

M. Bernoux : E. BlanchartIRD, UMR Eco&Sols,2 Place Viala,34060 Montpellier Cedex 1, France

S. De TourdonnetSupAgro Montpellier-IRC, UMR Innovation,1101 avenue Agropolis,34093 Montpellier Cedex 5, France

Agron. Sustain. Dev.DOI 10.1007/s13593-012-0106-9

participatory approaches needed to adapt conservation agri-culture principles to local conditions and farming systems aretop priorities for future research.

Keywords Soil fertility . Soil biology . Biodiversity .

Ecological processes . Environmental services . Cover crops .

Grain production . Farming systems . Brazil . Europe

Contents

1. Introduction ..................................................................22. Presenting Conservation Agriculture ...........................3

2.1. The underlying principles of ConservationAgriculture systems ........................................3

2.2. Different historical trajectories between Braziland Europe .......................................................4

2.3. Some examples of Conservation Agriculturesystems and their diversity in Brazil andEurope .............................................................4

3. Impacts of Conservation Agriculture systems on thesustainability of crops production: ...............................5

3.1. Soil erosion and physical properties .................53.2. Carbon dynamics and mitigation of the green-

house gas effect ................................................73.3. Water and Nitrogen efficiency ..........................83.4. Biodiversity and biological activity under

Conservation Agriculture systems ................103.5. Productivity and profitability of Conservation

Agriculture systems at field and farm levels .....104. Final considerations and perspectives: beyond the

Brazilian and the European experiences ....................115. Acknowledgements ....................................................136. References ..................................................................13

1 Introduction

Farmers from both developing and developed countrieshave to cope with several production constraints for achiev-ing a sustainable and cost-effective grain production.Depending on the context and the scale of farm operations,they are confronted with varying degrees of climate risksand economic uncertainties, e.g. fluctuating market prices,increasing production costs and decreasing levels of agri-cultural subsidies. There is also an increasing societal pres-sure to mitigate perceived or real negative impacts ofagriculture on the natural environment and on human health(eutrophisation, soil erosion, loss of biodiversity, pollutionby heavy metals, pesticides and nitrates, deforestation).Hence, there is an urgent need for more profitable, more

resilient and less risky cropping systems built on low-costtechnologies and causing minimal negative externalities.

In the humid and sub-humid tropics, climate is especiallyaggressive and soils are frequently deficient in nutrients andprone to erosion, while the rate of soil organic matter min-eralisation is usually high. For example, in Brazil, the use ofdisc ploughs for growing maize, soybean or sorghum hasinduced high levels of soil erosion in the first years ofcultivation following forest clearing, contributing in a con-text of low organic restitutions to the loss of up to 30–50 %of the initial soil organic matter (SOM) (Resck et al. 2000).Under such practices, yield potentials declined sharply overtime despite an increased use of chemical inputs and theintroduction of crop rotations (Séguy et al. 1996).

In temperate regions, where pedoclimate constraints aregenerally less compared to tropical conditions, levels ofSOM have decreased after decades of using conventionalplough-based systems (Balesdent et al. 2000). Yield potentialshave usually been maintained and often even increased, but asa result of applying increasingly higher levels of inputs in theform of energy, fertilizers, pesticides and labour. As a conse-quence, controlling environmental impacts and maintainingprofitability through cost reduction have become criticalissues for the farmers (Chevassus-au-Louis and Griffon 2008).

In response to the above challenges, farmers and agrono-mists have focussed on developing alternative croppingsystems over the past few decades. Conservation agriculture(CA) systems are among those that have been the mostextensively tackled. They rely on three so-called agronomicprinciples: (1) a significant reduction of soil tillage, (2) apermanent soil protection through at least partial soil mulch-ing and (3) increased biodiversity through diversification ofcrop rotations and/or intercropping. There is no set ofthresholds defining the degree to which such principlesshould be applied, but it is usually admitted that to beconsidered as conservation agriculture, cropping systemsshould involve at least simultaneous partial application ofeach of the three principles (http://www.fao.org/ag/ca/, Lal1997). Conservation agriculture systems have proved tobe efficient for the practical implementation of sustain-able crop production, particularly in terms of soil fertilitymanagement and soil productivity (Benites et al. 2003;Holland 2004; Calegari et al. 2008).

Regardless of the countries and cropping conditions, theexisting literature hardly expresses any doubt about theefficiency of conservation agriculture systems in mitigatingsoil erosion and soil degradation compared to conventionaltillage-based systems. These beneficial effects often seem toconstitute a major incentive to switch from conventional toconservation agriculture-based systems. Several authorsnote, however, that successful development and implemen-tation of conservation agriculture-based systems depend onmajor adaptations in crop management and farm

E. Scopel et al.

organization and on farmers’ steady access to the market(Affholder et al. 2010; Ekboir 2003), which impact directlyon natural resources dynamics and use efficiency and ontechnical and economical farm outcomes (Erenstein 2003;Bolliger et al. 2006; Lahmar et al. 2006). In the context ofsmallholder farmers of developing countries, some successstories have been reported in southern Brazil (Bolliger et al.2006), Paraguay (FAO 2002), the Ingo-Gangetic plains(Gupta and Seth 2007) or Zambia (Baudron et al. 2007).However, some authors (Giller et al. 2009; Serpantié 2009;Affholder et al. 2010) have recently argued against the wideapplicability and adoptability of conservation agriculture sys-tems due to the complexity of the required adaptations. It thusappears important to clarify where, when and why such con-servation agriculture systems may be efficient in producingmore or more sustainably, in comparison to conventionalsystems that are usually based on intensive soil tillage.

The objective of this paper is to review the impact ofconservation agriculture systems on crop productivity andsustainability. Our main focus is to contrast and comparetwo situations: (1) medium-size mechanized farms in Europeunder temperate climate conditions and (2) large-scale mech-anized and small-scale non-mechanized farms under the trop-ical climate conditions of the Cerrado region in Brazil. Manyreferences have been generated on conservation agriculture inthese two regions, and they can be considered, if not repre-sentative, at least typical of, respectively, temperate and trop-ical conditions in general. By contrasting results obtained bylarge-, medium- and small-scale farmers, we furthermore wantto contribute to a recurring debate about whether conservationagriculture implementation is indeed scale neutral. In bothcases, we assess the factors influencing the performance,impact and overall efficiency of conservation agriculture sys-tems from an agronomic and environmental perspective, tak-ing into account that they depend on specific pedoclimaticconditions and on actual farmers’ management practices.Finally, we identify key research areas which may contributeto a better understanding of conservation agriculture perform-ances and impacts and to a more efficient design of newconservation agriculture systems adapted to local situations.

2 Presenting conservation agriculture

2.1 The underlying principles of conservation agriculturesystems

CA systems are based on a handful of key agronomicprinciples, which, depending on whether they are appliedsimultaneously or partly, contribute to the overall capacityof these systems to optimize natural resources managementat the field level in the short and long term. The first threeprinciples have been described and recognized widely (e.g.

http://www.fao.org/ag/ca/). They are considered as the basisof the definition of conservation agriculture when they areapplied at least partially together:

1. Minimizing or suppressing soil tillage

In conservation agriculture systems, the soil should ideallynever been tilled, or as little as possible. The objective is tofavour a better cohesion between soil aggregates, decrease soilorganic matter mineralisation and allow the development of soilbiota. While no tillage is considered as the ideal, in many cases,however, farmers use reduced tillage, especially when they startto shift towards the practice of CA (Lahmar et al. 2006).

2. Protecting the soil surface through mulch

Under CA, crop residues or cover crops should be main-tained on the soil surface as a dead or live mulch. Theobjective is to protect the soil against weather aggressionsand water erosion, to maintain soil moisture (Lal 1997), tosuppress weed growth and to provide shelter and food forthe soil biota (Blanchart et al. 2006).

3. Rotating and/or associating crops

Use of crop rotations or intercropping is considered essentialin CA systems (Calegari 2001), as it offers an option for pest/weedmanagement that is no longer realized through soil tillage.Additionally, achieving greater biodiversity at the field andfarm level favours a better use of natural resources, a moreeven distribution of labour and more diversified farm incomes.

The next two principles, which are related to the threecited above, are less frequently mentioned in the literature,but they add important dimensions to a proper understand-ing and practical implementation of CA systems.

4. Producing biomass whenever possible

To improve the agro-ecosystem efficiency in using naturalresources, crops should be grown whenever possible duringthe whole year. If rains are too limited or too irregular to allowtwo commercial crops per year, cover crops are introduced atthe beginning or at the end of the growing period, i.e. warmor rainy season, to produce additional biomass, recy-cling water/nutrients which would otherwise be lostthrough leaching (Scopel et al. 2004b; Calegari 2006).Furthermore, those cover crops, when properly intercrop-ped with commercial ones, can increase significantly radia-tion interception by a plant canopy, during before or afterthe commercial crop cycle (Picard et al. 2010).

5. Introducing multifunctional cover crops

In addition to their role in fulfilling the functions alreadymentioned above, cover crops may fulfil additional agro-nomic, ecological or economical functions in CA systemsthat can supplement those performed by the main

Conservation agriculture performances and impacts

commercial crops (Anderson et al. 2001; Hartwig andAmmon 2002; Séguy et al. 2003). Cover crops may contributeto an increased total biomass production that allows mulchingthe soil permanently (Calegari 2006), even under humid trop-ical conditions where residues decompose rapidly. They mayalso contribute to the mineral nutrition of the main crop(s)through nitrogen fixation in the case of legumes, mulch min-eralisation or manure returns from animals that feed on them.Furthermore, part of the biomass they produce may contributeto farm incomes, e.g. additional grain production for humanfood or as extra fodder resources. Beside their above-groundfunctions, cover crops fulfil important functions below theground. Their root systems contribute to preventing or reme-diating soil compaction, re-structuring soil, tapping soil mois-ture from deeper horizons below the root zone of the maincrops or recycling nutrients such as nitrates, K, Ca and Mg thatare easily leached to deeper soil horizons (Barthès et al. 2005).

2.2 Different historical trajectories between Braziland Europe

Adoption of CA systems took off two to three decades ago,most notably in the USA, Canada, Australia, Brazil andArgentina. Nowadays, the area under CA has reached morethan 100 million ha worldwide (Derpsch et al. 2010). In Brazilfor example, the area under CA reached 25 million ha in 2006(FEBRAPDP 2010) and accounted for about 50 % of allBrazilian cropland. In the Cerrado region alone, CA systemsrepresent currently around 10 millions of hectares. Large-scalefarms, those cultivating thousands of hectares each, are respon-sible for most of the corresponding area. On the contrary,smallholder farmers, especially in the tropics, have adoptedCA on a much smaller scale (Scopel et al. 2004b).

In comparison to their American or Brazilian counterparts,European farmers have only started to adapt and adopt CAsystems, or components thereof, in recent years (Lahmar 2010).The area under CA management still remains modest through-out Europe, even though CA adoption is steadily increasingnowadays. In France for example, the area under CA wasestimated at 400,000 ha in 2001 but had increased to630,000 ha in 2006 (Benites and Ashburner 2001; Derpsch2001; Derpsch et al. 2008; Derpsch et al. 2010). Such figuresmask, however, an underlying variability in the extent of per-manent no-tillage use, as French farmers may use no-tillage forsome crops more than others and shift from no tillage toreduced or even full tillage from one cropping cycle to the next.One third of the grain production area is under reduced tillagemanagement in this country (Agreste 2008). Despite the presentinterest of the European farmers and of the European researchcommunity in CA practices, only few reviews exist on theperformance and impact of CA (Cannel 1981; Soane and Ball1998; Rasmussen 1999; Tebrügge and Düring 1999; Holland2004, Lahmar et al. 2006, Lahmar 2010).

2.3 Some examples of conservation agriculture systemsand their diversity in Brazil and Europe

In the Cerrado region of Brazil, the central savannah regionbetween 10° and 20°S latitude, the climate is humid. Annualrainfall varies between 1,200 and 2,000 mm and is concen-trated during 6 to 8 months of the year. Various CA systemswere developed in this region, and they mainly aimed atreducing soil erosion and better managing soil fertility(Figs. 1 and 2), while reducing production costs:

1. CA systems with two crops in succession annually: onecommercial crop such as soybean, rice or maize and asecond crop either grown for commercial purposes or asa cover crop, e.g. maize, millet, sorghum, Eleusine, torecycle nutrients. These systems are mostly used bylarge-scale farmers.

2. CA systems with one commercial crop such as rice ormaize, relayed by or intercropped with a cover crop(from the genera Brachiaria sp., Stylosanthes sp.,Crotalaria sp. and Cajanus sp.) which produces extraamounts of biomass at the end of the rainy season andcan be used either as green manure or grazed on the field(Scopel et al. 2004b). These more recently developedsystems are being applied with important amounts offertilizers by large-scale farmers and with very few chem-icals by small-scale mixed crop–livestock farmers.

In both types of CA systems, the five principles of CAlisted above are taken into account. As Brachiaria sp. orCajanus cajan are efficient forages, farmers may choose toconvert their cropped land into pasture or to keep it for grainproduction the following year. While soil fertility manage-ment and reducing tillage-related costs were the main con-cerns of the local farmers, little attention was paid to reducingpesticide use. Consequently, many of these systems, whenapplied by large-scale farmers, are very intensive with regardto input use (Scopel et al. 2004b). Very little information existson their impact on the environment.

In France (Fig. 3), the CA adaptation process is still in theinception phase, but the increasing suppression of ploughingopened new options for tillage practices that encompass thenon-inverting plough, shallow tillage, reduced number oftillage passes and direct seeding in mulched soil. Several ofthese practices may follow one another in time in the samefield and may coexist within the same farmland (DeTourdonnet et al. 2006). Recently, more attention has beenpaid on how to introduce cover crops, especially legumessuch as Alfalfa sp., in order to reduce herbicide require-ments, to increase nitrogen resources and to improve soilporosity (Carof et al. 2007b, c). This diversity of soil man-agement combined with several options of cover crops leadto a wide range of CA systems.

E. Scopel et al.

In both tropical and temperate regions, the translation intopractice of the key CA principles may lead to a large set ofpossible cropping systems, depending on the main crops, thecover crops, the level of external inputs and the managementoptions applied by farmers. In some situations, all principlesof CA systems are fully applied. In other situations, theprinciples are not completely or systematically applied, whichtends to open the range of possible CA-based options. On onehand, this wide diversity of technical options allows a greatflexibility to adapt CA principles to local farmer’s conditions.On the other hand, this diversity also influences strongly the

efficiency and the impacts of CA systems both in the short-and long-term, which we explain in the next section.

3 Impacts of conservation agriculture systemson the sustainability of crop production

3.1 Soil erosion and physical properties

In the tropical regions of Brazil, early studies showed thatCA systems based on no-tillage could reduce soil erosion

Fig. 1 Conservation agriculture systems in the Cerrado region in Brazil: a with two crops (commercial crop+Gramineae cover crop) in successionunder direct seeding, b with two crops (commercial crop+Gramineae and/or legume cover crops) in relay under direct seeding

Conservation agriculture performances and impacts

loss by a factor of 2 (Dedecek et al. 1986) to 20 (Castro et al.1986) depending on the slope and soil texture. It is com-monly known that under tropical climate, mulching withcrop residues is particularly efficient in controlling erosionprocesses through dissipating the energy of rainfall impact(Hernani et al. 1997) and reducing runoff fluxes (Da Silva2004).

Measurements performed in France and Europe con-firmed the capacity of CA systems to reduce soil erosion;even under reduced tillage two to ten times less erosion wasreported (Bonafos et al. 2007). Under temperate conditions,reduced erosion results mainly from increased stability ofthe topsoil aggregates and an increased water infiltrationrate, both of which are closely related to soil organic matter

Fig. 2 Photos illustratingconservation agriculture useunder Brazilian tropicalconditions:a mechanized direct drillingunder large-scale farmsconditions (source: Embrapa),b mechanized cotton growingon a dead residue mulch ofBrachiaria sp. (source: E.Scopel), c direct drilling withanimal traction under small-scale farms conditions (source:C.F.D. Alencar Ribeiro) and dmaize with a relay cover crop ofC. cajan under small-scalefarms conditions (source: E.Scopel)

Fig. 3 Photos illustratingconservation agriculture useunder French temperateconditions:a mechanized cover cropmanagement before drilling(source: Unknown),b mechanized crop drilling(source: Unknown),c wheat growing on deadresidue mulch of Gramineae(source: S. De Tourdonnet) andd wheat growing on a livingcover crop of alfalfa (source: S.De Tourdonnet)

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(SOM) and earthworm activity (Friebe and Henke 1991;Puget et al. 1995; Balabane et al. 2005). The benefitsobtained under CA systems are often explained by increasedsoil porosity and high quantities of surface crop residues(Kwaad et al. 1998; Quinton and Catt 2004; Heddadj et al.2005). On the other hand, CA systems tend to become ineffi-cient for controlling erosion if not enough crop residues areavailable to protect the soil surface (Heddadj et al. 2005).

In many situations, it has been observed that problems ofsoil compaction can occur under CA. These have to beoffset by an enhanced biological activity, mimicking theprocesses under natural vegetation. Under temperate condi-tions, during the initial years of CA practices when tillageoperations are still performed to a certain degree, soil po-rosity may decrease, even though increased porosity withno-till practices has been reported by some authors withimportant returns of organic residues (Douglas et al. 1986;Tebrügge and Düring 1999). Under tropical conditions,macrofauna populations and their activity are largely stim-ulated when large amounts of crop residues are returned tothe system (Blanchart et al. 2007) contributing to soil po-rosity enhancement. Some cover crop species such asBrachiaria sp., Eleusine sp., Andropogon sp., Cynodon sp.for tropical conditions (Blanchart et al. 2004; Mannetje2007) or Lolium sp., Alfalfa sp., for temperate conditions(Carof et al. 2007a) may be very efficient in restoring thesoil structure because of their substantial rooting systems,especially in the 0–40-cm soil layer. In contrast, where covercrops are not or only irregularly used, some limited

compaction can appear as it has been reported by Stoneand Moreira (2000) in Brazil, especially during the initialyears of CA introduction (Ralisch et al. 2008).

3.2 Carbon dynamics and mitigation of the greenhouse gaseffect

In the Cerrado region (Table 1), studies have reported higherC stocks in CA systems compared to conventionally tilledsystems (Corazza et al. 1999; Bayer et al. 2004), with Cstorage rates under CA varying from 0.4 to 1.9 Mg Cyear!1 ha!1 for the 0–40-cm layer (Bernoux et al. 2006).In this region, the accumulation of organic C in the soilunder CA systems seems to occur only when nitrogen is notlimiting (Mielniczuk et al. 2003; Roscoe et al. 2006) andwhen rates of organic returns are large, i.e. generally morethan 12 Mg dry matter ha!1 (Corbeels et al. 2006). Metay etal. (2003) demonstrated that due to favourable conditionsfor decomposition, i.e. high temperature and moisture,quicker drainage after heavy rains, CO2 emission related toheterotrophic microbial activity is greater in CA systemsthan in conventional systems. However, C losses throughdecomposition are largely compensated by returns in theform of crop residues since the total biomass produced ina two-crop CA system may be twice or three times higherthan in conventional systems with one crop per year(Bustamante et al. 2006; Scopel et al. 2004b).

Available studies (Table 1) show that C accumulationrates under CA are generally lower in France than in the

Table 1 Carbon storage rates (accumulation following conversion of a conventional tillage system to conservation agriculture) under conservationagriculture systems in Europe and Brazil

Place State Succession ordominant plant

Reported soilclassification

Clay (%) Layer (cm) Duration(years)

Rate (t C/ha/year) Source

Cerrados region

Planaltina DF S/W Latosol (Oxisol) 40–50 0–20 15 0.5 Corazza et al. 19990–40 15 0.8

Sinop MT R–S/So–R/So–S/M–S/E Latosol (Oxisol) 50–65 0–40 5 1.7 Perrin, 2003

Planaltina DF M or S Dark Red Latosol(Oxisol)

>30 0–40 16 0.4 Resck et al. 2000

Goiânia GO R/S Dark red Latosol 0–10 5 0.7 Metay et al. 2007a

Rio Verde GO M or S/Fallow Red Latosol 45–65 0–20 12 0.8 Corbeels et al. 2006S/M or So or Mi

Rio Verde GO S/M or So or Mi Red Latosol 48–68 0–30 12 1.9 Siqueira Neto et al.2010

France

Synthesis Multiple Various grains Multiple d.n. d.n. Multiple 0.2 Arrouays et al. 2002

Boigneville PB M/W Haplic Luvisol 22 0–30 20 0.2 Balesdent 2002

Boigneville PB M/W Haplic Luvisol 22 0–30 28 0.1 Metay et al. 2009

Source: Bernoux et al. (2006), completed with temperate and more recent tropical studies

DF Distrito Federal, MT Mato Grosso, GO Goiás, MG Minas Gerais, PB Parisian Bassin, S soybean (Glycine max), So sorghum (Sorghumvulgaris), R rice (Oriza sativa), W wheat (Triticum spp.), E Eleusine coracana, M Maize (Zea mays), B beans (Phaseolus vulgaris), G Guandu (C.cajan), d.n. data not given

Conservation agriculture performances and impacts

tropical region of Brazil, ranging from 0.1 to 0.4 Mg Cyear!1 ha!1 for the 0–20-cm layer (Balesdent et al. 2000;Arrouays et al. 2002). Under these temperate conditions too,the amounts of crop residues retained on the soil surfacehave been shown to be a key factor for the rates of soil Caccumulation in CA (Arrouays et al. 2002). In general, theamount of biomass produced by the commercial crop isequal or slightly lower in CA or reduced tillage systemscompared to conventional ones (Agreste 2008). The lowrates of organic restitution in the long-term experimentscarried out in France may explain the lower carbon accu-mulation rates reached, compared to the results in tropicalclimate (Lahmar et al. 2006).

Other studies carried out in Brazil and Europe reportedthat organic C contents under CAwere very similar to thoseof conventional systems (Freixo et al. 2002; Roscoe andBuurman 2003; Sisti et al. 2004; De Tourdonnet et al. 2007).These contradictory results can be explained by differencesin soil clay contents inducing differences in stabilisation ofSOM (Feller and Beare 1997; Six et al. 2002) combinedwith different amounts and qualities of the returned cropresidues linked with crop rotations, choice of cover cropsand level of inputs used (Lal 1997; Metay et al. 2007a).

The favourable impact of CA systems on slowing downglobal warming through soil C sequestration could, however,be offset by increased emissions of other greenhouse gases,especially nitrous gases. In the Cerrado region, N2O emis-sions have been found to be very low (<1 g N2O–N ha!1 day!1) for both CA and conventional systems dueto the natural high aggregation of the Oxisols and theirsubsequent high drainage capacity (Metay et al. 2007b). Incontrast, in temperate regions, some studies have shown aslight increase in N2O emissions (+0 to 5 kg N-N2O ha!1 year!1) under CA compared to conventional man-agement (Li et al. 2001; Six et al. 2002; Smith and Conen2004; Oorts et al. 2006). These higher N2O fluxes may beexplained by a decrease in soil porosity combined withhigher soil moisture and higher SOM concentrations in theupper soil layer in the non-tilled soils. However, the expectedlong-term improvement of biological porosity in CA systemsshould contribute in decreasing these differences (Six et al.2004; Oorts et al. 2006; Nicolardot et al. 2007).

3.3 Water and nitrogen efficiency

In both regions, the presence of a permanent mulch of cropresidues in CA systems considerably modifies the cropwater balance (Kwaad et al. 1998; Da Silva 2004). Firstly,surface water runoff is generally reduced with CA systems(Table 2). Depending on the soil type, the amount of resi-dues, the slope, the type of crop and its development,between 0 and 85 % reductions have been observed in theBrazilian tropics compared with conventional systems

(Schick et al. 2000; Levien and Cogo 2001; Mello et al.2003; Scopel et al. 2004a). Similarly in France, runoff in CAsystems was found to be one to five times less than inintensively tilled systems (Bonafos et al. 2007).

In both contexts, CA systems can induce higher infiltra-tion rates, being sometimes almost double of those of con-ventional systems (Friebe and Henke 1991; Castro and DeMaria 1993; Kwaad et al. 1998; Alves and Cabeda 1999).The improvement of soil infiltration in CA systems is theresult of (a) the increased roughness and complexity of theflow path which slows down the water flow rate across thesoil surface (Kwaad et al. 1998; Da Silva 2004) and (b) theimproved topsoil porosity mainly due to increased macro-fauna activity and less soil crusting (Friebe and Henke 1991;Castro and De Maria 1993; Kwaad et al. 1998). Furthermore,the mulch limits the amount of solar energy reaching the soilsurface, thus decreasing the first-stage evaporation of soilwater by 10 to 50 % depending on the amount ofmulch cover. This is particularly important under thehot and sunny conditions of the tropics (Da Silva etal. 2006; Scopel et al. 2004a). As a result, water is storedmore quickly in the soil profile under CA systems at thebeginning of the rainy season in the tropics and during winterand spring in the temperate regions, which can act as a bufferagainst the effects of an eventual dry spell at the early stage ofthe crop cycle (Reyes Gomez et al. 2002; Da Silva 2004;Scopel et al. 2004a).

Due to the mulch, CA systems generally provide temper-ature and moisture conditions that favour a more regularSOM decomposition throughout the crop cycle and a highernitrogen (N) availability for the commercial crop (ReyesGomez et al. 2002; Balota et al. 2004; Metay et al. 2003).Maltas et al. (2007) reported that in Brazil, N mineralisationcould increase by 2 kg of N ha!1 year!1 in CA system due tothe improvement in soil organic C and N stocks.Furthermore, part of the soil mineral N supply is providedby the decomposition of the previous crop residues. Forboth kind of climates, the amount and dynamics ofresidue-derived N mineralisation depends on the type ofwinter crop, its productivity and the C/N ratio of its residues(Calegari 2000; Primavesi et al. 2002; Da Silva et al. 2006;Abiven and Recous 2007; Maltas et al. 2009). Nevertheless,N immobilisation can be observed in some situations, suchas with some cereals or old pasture straws, having high C/Nratio (Bayer and Mielniczuk 1999; Ernani et al. 2002; Bertolet al. 2004). In contrast, the introduction of legumes as covercrops in CA systems increases subsequent soil mineral Navailability, allowing to reduce the use of chemical N fertil-izers on the following maize crop (Spagnollo et al. 2002;Carvalho et al. 2004; Zotarelli et al. 2004; Balde et al. 2011).However, in the case of legume cover crops under tropicalconditions with fast decomposition rates, synchronizationbetween the residue N mineralisation and the N requirements

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of the next commercial crop is difficult to control, whichaffects the system’s efficiency (Giller 2001). Sometimes mix-ture of various cover crops with different qualities of residuemay contribute to a more regular mineralisation processthroughout the cycle of the subsequent commercial crop(Maltas et al. 2009).

In humid tropical regions, such as the Cerrado, waterdrainage fluxes are important because of high rainfallamounts. As a consequence of the better water conservationdue to the mulch, the probability of increasing the drainageduring the commercial crop cycle with CA systems is sig-nificant, especially during very rainy years, for soils havinglimited water storage capacity and with large amounts ofresidues (Scopel et al. 2004a). While conventional systemsonly have one commercial crop a year, many CA systemsinclude a second crop after the commercial one, which canuse the additional water stored at the end of the first cropcycle. This significantly limits total yearly drainage (Scopelet al. 2004b).

Water dynamics have direct consequences on N efficien-cy. Indeed, when no cover crop is introduced in the annualsuccession in the tropical Cerrado, a large accumulation ofmineral N is observed at the beginning of the followingrainy season and at the beginning of the next commercial

crop cycle (Reyes Gomez et al. 2002). As the crop Nrequirements are small at the early stages of development,the risk of N leaching is very important with intensivetropical rainfall. In contrast, in CA systems with a covercrop, the soil mineral N pool across the soil profile is emptyat the beginning of the new season as N has been taken upby the cover crop. N is then slowly supplied back to thesystem through mineralisation (Maltas et al. 2009; Abivenand Recous 2007). Even with higher risks of drainage in thepresence of a mulch of residues during the main crop cycle,N leaching can thus be reduced by 30 % with CA systemsdue to the presence of the cover crop (Reyes Gomez 2002).

Under temperate conditions, nitrate losses may occur innon-tilled soils when significant macro-pore flow relocatesthe nutrients into subsurface layers (Kohl and Harrach1991). However, several studies showed a significant de-cline in nutrient (N, P and K) losses in soils with reducedtillage compared to conventional ploughing (Tebrügge andDüring 1999; Korsaeth and Eltun 2000). The processesinvolved are (a) water infiltration occurs mostly in macro-pores and channels, bypassing the soil matrix, so avoidingintensive exchange with the soil and preventing nutrientsfrom being leached (Tebrügge 2001) and (b) the peak of Nmineralisation is lower when ploughing is abandoned (Riley

Table 2 Impact of conservation agriculture systems on runoff losses in different situations in Brazil and Europe

Ref. Soil Slope Texture or %of clays

Runoff with conservationagriculture systems(% of rainfall or mm)

Runoff withconventionalsystems (%of rainfall or mm)

Brazil

Schick et al. 2000 Inceptisol 10.0 % Clay 9.9 % 20.4 %

Levien and Cogo 2001 Typic Hapludulf 12.0 % Sandy loam 21.2 % 41.5 %

Bertol et al. 1997 Paleudult 6.6 % Sandy clay 7.3 % 26.1 %

Alves and Cabeda 1999 Paleudult 5.6 % Sandy clay 50.0 % 83.5 %

Mello et al. 2003 Hapludox 18.0 % Clay 30.0 % 38.0 %

Reyes Gomez et al. 2002 Oxisol 3.0 % Clay 5.5 % 11.0 %

Scopel et al. 2004a Oxisol 4.0 % Clay 20.0 % 35.0 %

Europe

Quinton and Catt 2004 Lamellic Ustipsammentand Udic Haplustept

7.0 to 13.0 % Loamy sand to sandyloam (6 % clay)

29.0 % 34.0 %

Heddadj et al. 2005 Loamy soils 6.0 % 16.5 % of clay 22.0 mm 13.0 mm

6.0 mm 3.0 mm

Kwaad et al. 1998 Loess soils 7.7 to 9.2 % 16.0 % of clay 2.0 mm 4.5 mm

1.7 mm 2.6 mm

22.3 mm 14.8 mm

3.7 mm 4.6 mm

Bonafos et al. 2007 (synthesis) Several Several Several From 1 to 0.2!A%(function of soilcover, texture andslope)

A%

Conservation agriculture performances and impacts

et al. 2005). Also, catch crops used in CA systems can lowerthe risk of leaching (Breland 1995; Molteberg et al. 2004),especially when they are intercropped with the main com-mercial crop (Shili-Touzi et al. 2010).

3.4 Biodiversity and biological activity under conservationagriculture systems

In both tropical and temperate conditions, soil biologicalactivity and diversity are higher in systems with reducedor no tillage and with a surface mulch or cover crops (Friebeand Henke 1991; Clapperton 2003; Blanchart et al. 2006;Brevault et al. 2007; De Aquino et al. 2008; Rabary et al.2008). In the Brazilian Cerrado, different studies showed ahigh increase in soil macrofauna density under non-tilledCA systems compared to conventional systems (Brown etal. 2001; Blanchart et al. 2007). This increase is mainlyattributable to earthworms and the reappearance ofColeopteran larvae. Blanchart et al. (2007) observed underCA a strong relationship between macrofauna biomass andsoil C stock. Under European temperate conditions, the CAsystems with tillage reduction and crop residue retention onthe soil surface favour the proliferation of slugs, snails andmice (Symondson et al. 1996; Kreye 2004), along withincreased density and diversity of Carabidae, spiders andnematodes (Hulsmann and Wolters 1998; Andersen 1999)and improved abundance and biomass of earthworms(Emmerling 2001).

Studies on microbial biomass in the Cerrado Oxisolsmanaged under CA systems have given contradictoryresponses, with some studies showing increases (Mendeset al. 2003) and others showing no differences in soil mi-crobial biomass when compared with conventional systems(Mendes et al. 2005; Borges et al. 2007). Higher activities of!-glucosidase, acid phosphatase and arilsulfatase enzymeshave been reported in the 0–10-cm layer with CA systems(Mendes et al. 2003; Mendes and Reis Junior 2004), sug-gesting that these systems provide a more favourable habitatfor microorganisms. Under temperate conditions, manystudies have shown increases in microbial biomass of 30to 100 %, in the soil surface layers when ploughing issuppressed, often inducing higher N mineralisation andenzymatic activities (Ahl et al. 1998; Díaz-Raviña et al.2005; Piovanelli et al. 2006). However, this improvementof microbial activity is not systematic (Dilly et al. 2003;Maurer-Troxler et al. 2006; Ulrich et al. 2006) and is fre-quently restricted to the topmost centimetres of the soilprofile (Dilly et al. 2003) and directly related with theamount of organic residues returned to the system.

Another important aspect of biodiversity is related toweed, pest and disease dynamics which have direct conse-quences on the management of the cropped fields. CAsystems have been held responsible for a significant increase

in the use of chemicals, mainly herbicides. Nevertheless,actual use of pesticides, i.e. products, doses, frequency ofapplications, under CA vs. under conventional systemsneeds to be assessed very carefully. For example, for inten-sive maize production in the Cerrado region, while systemicherbicides such as glyphosate or 2,4-D have been morewidely applied in CA systems, doses of very remnant pre-emergent herbicides based on atrazine and simazine werereduced by almost a factor of three (Scopel et al. 2004b). InEurope, higher weed infestations have been reported underreduced tillage, with a higher diversity and abundance ofbiennial and perennial species (Debaeke 1987; Debaeke andOrlando 1994). Consequently, an average of 1.7 applica-tions is necessary for producing wheat under no till com-pared to 1.4 with tilled systems (Agreste 2008). However,this increase can be avoided with CA systems, as severalexperiences have demonstrated the role of crop rotations andcover crops to better control weeds and pests in such sys-tems (Breland 1996; Brandsaeter et al. 1998; Médiène et al.2011).

Very little is known about the fate of pesticides under CApractices in Europe and even less in the Brazilian Cerrado(Christoffoleti et al. 2008). Results obtained in Germanyclearly showed that as SOM accumulated in the upper layerof soils under CA, pesticides were susceptible to be fixed inthis layer, being less prone to leach down the soil profile(Real and Heddadj 2005). Moreover, losses of agrochemi-cals via surface runoff were clearly reduced under no-tillconditions (Tebrügge and Düring 1999). Fixation and accu-mulation of pesticides molecules in the topsoil layers underCA theoretically leave more time for microbial activity todecompose them (Real and Heddadj 2005). However, morestudies are needed to quantify the rate of pesticide bio-recycling in both types of cropping systems.

3.5 Productivity and profitability of conservation agriculturesystems at field and farm levels

In the Cerrado region, the productivity of soybeans underCA on large-scale farms has tended to increase with timewhen compared with conventional monoculture systems.This can be attributed to better SOM management in sit-uations where soil fertility has declined (Séguy et al. 2003).In the Cerrado, total annual dry matter production, aboveand below ground, increased from 4 to 8 Mg ha!1 in theconventional systems with a single soybean crop, to anaverage of over 15 to 25 Mg ha!1 in CA systems with covercrops (Kluthcouski et al. 2007). When a second commercialcrop is introduced in the rotation, grain production mayincrease by up to 1.5 to 1.8 times compared with a singlecrop system (Scopel et al. 2004b). In the case of smallholderfarmers, actual productivity achieved depends on the farm-ers’ capacity to control weeds at the beginning of the cycle.

E. Scopel et al.

If they are able to ensure a good seeding and total weedcontrol at crop germination, they generally stand a goodchance of increasing their crop yields, especially with maize(Da Silva et al. 2009, Balde et al. 2011).

In the case of Europe, CA systems in general do notgenerate yield increases. The improvement or the stabilisa-tion of yields does not appear to be critical to farmers whenthey decide whether or not to adopt CA systems (Lahmar2010). On average, yields obtained by French farmers onpoor and average agricultural lands change little under CA(±10 %) (Agreste, 2008); yields may, however, decrease byabout 10 to 20 % on fertile lands under intensive production(Bertrand et al. 2005). This yield decrease of the commercialcrop may be accentuated in case of a significant competitionwith a cover crop (Shili-Touzi et al. 2010). Such competitionmay, however, be avoided when using proper sowing datesand exploiting differences in growth dynamic between bothspecies(Ghiloufi et al. 2010; Balde et al. 2011).

In terms of economical return and profitability, tillagesuppression may substantially reduce crop production costs,as mechanized tillage is a rather costly technique includingfuel, labour and machinery costs. In the intensive grainproduction systems practiced by large-scale farmers of cen-tral Brazil, relative benefits of CA depends on the differencebetween the cost of land tillage vs. the cost of herbicidesapplied before sowing. Nowadays, total herbicides, such asglyphosate, are relatively cheap, stimulating their wide useby CA farmers (Landers et al. 2008). Studies on Brazilianlarge-scale farms demonstrate similar economical resultsfrom CA vs. conventional systems in the first years of CAapplication and better economical results for CA once theyare stabilised (Fontaneli et al. 2000). Small holders in thesame region need to purchase specific manual or oxen-drawn equipment such as sprayers, direct planters, to prac-tice CA. This equipment is widely available in Brazil at veryaccessible prices (Ribeiro 2003). The economic results ofCA for small farmers depends on the relative cost of landpreparation and labour for the manual control of weedsversus the cost of buying and applying herbicides (Alvarez2007). Weeds have severe consequences on crop productiv-ity under tropical conditions, so profitability of CA dependson whether weeds are correctly controlled or not (de Oliveiraet al. 2009). Small-scale farmers are steadily increasing theirherbicide use throughout Brazil (Da Silva et al. 2009), andtheir capacity to use these products efficiently, and hence tocontrol weeds better, has improved considerably.

Furthermore, CA has introduced in this region greaterflexibility into the organization of farm activities by reduc-ing labour peaks and offering the opportunity of optimizingplanting dates (Scopel et al. 2004b). For smallholder farm-ers, CA can increase labour efficiency through the use ofexternal inputs and/or equipment, e.g. herbicides for weedcontrol or special equipment for planting operations

(Ribeiro 2003). Various studies made in the Brazilian con-text have shown a reduction in labour requirements of 11 toalmost 40 %, mainly due to reduced soil tillage, reducedmanual/mechanical weed control and the suppression ofother anti-erosion practices such as terraces or contourplanting (Ribeiro et al. 2007; De Oliveira et al. 2009).

In Europe, farmers are more concerned by the short-termbenefits from applying CA systems such as reduced labourand fuel costs (Lahmar et al. 2006). However, achieving thisreduction depends on many factors such as the type of soil,crop and machinery, and the savings may be offset byadditional costs due to heavy infestations of weeds, pestsand diseases. Such problems may lead farmers to favourspecific crops that are more easily managed with CA, suchas maize, soybean, canola or to turn back to conventionalpractices.

4 Final considerations and perspectives: beyondthe Brazilian and the European experiences

From a biophysical/agronomic perspective, this comparativereview has shown that conservation agriculture systemsrepresent a diversified set of options offering farmers thepossibility to achieve sustainable and intensive crop produc-tion under a wide range of agroecological environments, beit under temperate or tropical conditions. They simulta-neously allow to maintain or enhance soil fertility by reduc-ing soil erosion, increasing SOM, enhancing soil porosityand to make efficient use of available natural resources suchas radiation, water and main nutrients. Such effects are indirect relation to the presence of a protecting mulch of cropresidues and the incorporation of multifunctional covercrops into the cropping system. If mulching rates are toolow and cover crops are not introduced, such benefits aremuch reduced, or even absent. From a socioeconomic per-spective, conservation agriculture systems have been shownto be generally profitable if their adoption translates in lowerproduction costs, starting with the quasi-suppression of theland preparation costs, coupled with the maintenance or anincrease in grain yields. Under appropriate management, i.e.without problems of crop establishment, weed and/or pestcontrol, the labour requirements and costs may decline.Usually, for both resource use efficiency and socioeconom-ical results, the situation becomes more favourable aftersome years of conservation agriculture application whensystems stabilise.

Despite these agro-environmental and economic potentialbenefits, conservation agriculture systems are no panaceafor solving all problems related to agricultural sustainabilityas repeatedly claimed by some authors and throughout theinternational conservation agriculture community (Benitesand Ashburner 2001; Ribeiro 2003; Derpsch 2005). Other

Conservation agriculture performances and impacts

authors have stressed the difficulties in applying and adopt-ing efficiently conservation agriculture technologies in thecontext of small-scale farming (Affholder et al. 2010). This isparticularly argued in Africa, where traditional organization ofrural activities and a strong competition for biomass use withgrazing or fodder represent very strong limitations for adop-tion of conservation agriculture (Giller et al. 2009; Serpantié2009). On the basis of this review, and looking beyond thespecific experiences and conditions of Brazil and Europe, wecan draw the limits of our actual knowledge and the limits ofthe efficiency of such systems.

The need for additional research on CA systems and theecological processes they modify is still very urgent. Forexample, the success of conservation agriculture systemsrelies on the modification of the availability and evolutionof the main resources and on the efficiency by which theyare used by the plants growing in the field. While the mech-anisms are usually the same as in non-conservation agriculturesystems, context and fluxes are modified. Gaining a clearunderstanding of the functioning of conservation agriculturesystems implies a very accurate characterization of environ-mental modifications and measurements of those fluxes,which both require precise experiments and equipments.Carbon storage rates for example (Table 1) are too variableto characterize precisely those systems and anticipate theirevolution. Modelling these processes (Corbeels et al. 2006;Shili-Touzi et al. 2010) gives a better idea of their dynamics,but some of these models require precise parameters and datathat are not always available in tropical countries. The samecould be said for the water and any other resource cycle.

It has been shown in section 3 of this paper that actual, asopposed to potential, agronomical and ecological efficiencyof conservation agriculture systems depend greatly on thecapacity of the farmers to apply simultaneously and/or com-pletely the major conservation agriculture principles. Forexample, tillage suppression is quite efficient for erosioncontrol or for reducing energetic costs but the CA systemsusually requires farmers to use herbicides or else to investmore in mechanical or manual weeding, at least in the initialyears. This is something which may not be desirable and insome cases not possible for several reasons (Baudron et al.2007; Ribeiro et al. 2007; Affholder et al. 2010). Tillagesuppression also needs to be compensated by an increasedbiological activity or biodiversity to reduce weed pressureand to enhance soil structure and soil porosity (Blanchart etal. 2004; Carof et al. 2007b). In some instances, however,farmers do no suppress soil tillage completely, when they donot have easy access to a direct driller or to herbicides(Baudron et al. 2007).

Additionally, most ecological functions of the system arestrongly linked with the introduction and the specific char-acteristics and effects of cover crops: total biomass produc-tion, erosion control, soil restructuration, C storage in soil,

soil biological activity, fertility improvement, nitrogen in-troduction, nutrient cycling and long-term weed control(Anderson et al. 2001; Scopel et al. 2004b). But cover crops,or any additional biomass produced, should provide someeconomical use and return in the short-term for farmers,large-scale and small-scale ones alike, to have the sufficientincentive for introducing them. Long-term profitabilitythrough fertility improvement and through integrated weedmanagement is indeed often not sufficient to convince farm-ers to use them (Erenstein 2002; Giller et al. 2009). In someinstances for example, farmers export a significant part ofthe crop residues for use as fodder, fuel or constructionmaterial, rather than for use as mulch, particularly in thecase of tropical smallholder farmers when customary lawsallow cattle from shepherds to graze on farmers’ fields(Dugué et al. 2004; Baudron et al. 2007). In some casestoo, farmers do not introduce cover crops because there areno seeds available, no markets for selling them and even ifthere were, they would displace an existing food crop, suchas beans or cowpeas, to plant them. In other cases, they donot introduce them because their management would requirea lot of labour (Anderson et al. 2001). Finally, even if thereare clear indications about conservation agriculture bio-physical and agronomical positive impacts, many unknownsremain about the continuous and complete trades-off inreducing tillage versus soil erosion or weeds control effi-ciency, or about exporting biomass versus soil protection,soil C storage or nutrient balance.

In comparison with an “ideal” conservation agriculturesystem from a purely agronomic viewpoint combining all fiveconservation agriculture principles or at least the three majorones, farmers may hence decide to implement sub-optimalsystems, i.e. with partial application of these principles, offer-ing them partial benefits, depending on their circumstances andobjectives. Unsurprisingly, they usually tend to select thosesystems and components which allow them to optimize theirshort-term economic gains. In doing so, they willingly sacrificepartly those systems and components linked to longer-termecological benefits (Affholder et al 2010). As a consequence,they may need to mobilise periodically external inputs such astillage, labour or fertilizers, to compensate for eventual re-source degradation caused by leaving out specific conservationagriculture principles, components or ecological functions. Amajor issue hardly addressed until now is to predict the con-sequences of each of these partial systems and to know howmuch compensation will be necessary in each case.

As stressed by Giller et al. (2011), we do believe that thisis probably one of the domains where agronomic researchshould focus its main efforts in the near future, clarifyingwhat these trade-offs are in different contexts and creatingsome modelling tools for simulating/extrapolating them.This kind of knowledge would enable local actors to guidethe process of adapting conservation agriculture cropping

E. Scopel et al.

systems to their own situations and needs and, in doing so,match them more efficiently to their main limiting factorsand optimise their own resources and priority economicbenefits (Mischler et al. 2008).

Adoption of conservation agriculture systems byfarmers is often limited by the fact that they are quitedifferent from the conventional plough-based systems.Concretely, farmers willing to shift to conversation ag-riculture face several challenges: (1) they need to learnabout ecological principles which often tend to remaintheoretical/abstract, (2) they have to learn a series ofstrongly inter-related new crop management techniques,and in particular those related to proper weed andresidue management, (3) at farm level, the introductionof such different technologies will modify significantlythe organization of the farming activities and the wayproduction factors are used, and finally, (4) farmersgenerally perceive that the risk of failure is importantwhen introducing conservation agriculture, especially inthe initial years, and they often require technical assis-tance and even financial assistance, in particular smallholder farmers.

More specific studies on how to overcome such limita-tions and how to enhance farmers’ adoption and adaptationare thus necessary. If and when their main principles arecorrectly applied, conservation agriculture systems may rep-resent interesting options to achieve a sustainable crop pro-duction, both under temperate and tropical conditions, bothfor large- and small-scale farmers. Nevertheless for theirefficient, development and wide diffusion, further scientificprogress has to be made to better understand what the bestconditions are to apply them, what flexibility exists inapplying them and how to better enhance local innovationprocesses around conservation agriculture.

Acknowledgments This work was partly funded by the AgenceNationale de la Recherche under the Systerra Program: ANR-08-STRA-10 (Ecological, technical and social innovation processes inConservation Agriculture).

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