Conservation Agriculture Spread Justification, Sustainability and Uptake

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The spread of Conservation Agriculture:justification, sustainability and uptakeAmir Kassam a , Theodor Friedrich b , Francis Shaxson c & Jules Pretty da School of Agriculture, Policy and Development, University of Reading,Whiteknights, PO Box 237, Reading, UKb Plant Production and Protection Division, Food and AgricultureOrganization (FAO) of the United Nations, Viale delle Terme di Caracalla,00153, Rome, Italyc Tropical Agriculture Association, PO Box 3, Penicuik, Midlothian, EH26 0RX,UKd Department of Biological Sciences, University of Essex, Wivenhoe Park,Colchester, Essex, CO4 3SQ, UKPublished online: 08 Jun 2011.

To cite this article: Amir Kassam , Theodor Friedrich , Francis Shaxson & Jules Pretty (2009): The spreadof Conservation Agriculture: justification, sustainability and uptake, International Journal of AgriculturalSustainability, 7:4, 292-320

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The spread of Conservation Agriculture: justification,sustainability and uptake1

Amir Kassam1,*, Theodor Friedrich2, Francis Shaxson3 and Jules Pretty4

1School of Agriculture, Policy and Development, University of Reading, Whiteknights, PO Box 237, Reading, UK;2Plant Production and Protection Division, Food and Agriculture Organization (FAO) of the United Nations, Vialedelle Terme di Caracalla, 00153 Rome, Italy; 3Tropical Agriculture Association, PO Box 3, Penicuik, Midlothian,EH26 0RX, UK; and 4Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex,CO4 3SQ, UK

Conservation Agriculture (CA) has been practised for three decades and has spread widely. We estimatethat there are now some 106 million ha of arable and permanent crops grown without tillage in CAsystems, corresponding to an annual rate of increase globally since 1990 of 5.3 million ha. WhereverCA has been adopted it appears to have had both agricultural and environmental benefits. Yet CArepresents a fundamental change in production system thinking. It has counterintuitive and oftenunrecognized elements that promote soil health, productive capacity and ecosystem services. Thepractice of CA thus requires a deeper understanding of its ecological underpinnings in order tomanage its various elements for sustainable intensification, where the aim is to optimize resource useand protect or enhance ecosystem processes in space and time over the long term. For thesereasons CA is knowledge-intensive. CA constitutes principles and practices that can make a majorcontribution to sustainable production intensification. This, the first of two papers, presents thejustification for CA as a system capable of building sustainability into agricultural production systems.It discusses some of CAs major achievable benefits, and presents an overview of the uptake of CAworldwide to 2009. The related paper elaborates the necessary conditions for the spread of CA.

Keywords: Conservation Agriculture, conservation tillage, no-till, soil health, sustainability, technologyadoption, tillage practices

Introduction

The challenge of agricultural sustainability hasbecome more intense in recent years with thesharp rise in the cost of food and energy, climatechange, water scarcity, degradation of ecosystemservices and biodiversity, and the financial crisis.The expected increase in population and the associ-ated demands for food, water and other agriculturalproducts will bring additional pressures. In recent

decades, the development community includingpoliticians, policy makers, institutional leaders aswell as academics, scientists and extensionworkers have been highlighting the need for thedevelopment of sustainable agricultural systems.In response to this, action has been promoted atall levels and yet, as witnessed in the MillenniumEcosystem Assessment (MEA, 2005), the WorldDevelopment Report 2008 (WDR, 2008) and theIAASTD reports (McIntyre et al., 2008), someagricultural systems are still being promoted withunacceptably high environmental, economic andsocial costs, albeit with the promise of gains

*Corresponding author. Email: amirkassam786@googlemail.

com

doi:10.3763/ijas.2009.0477

INTERNATIONAL JOURNAL OF AGRICULTURAL SUSTAINABILITY 7(4) 2009, PAGES 292320# 2009 Earthscan. ISSN: 1473-5903 (print), 1747-762X (online). www.earthscanjournals.com

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in output. Consequently, business-as-usual withregards to agricultural development is increasinglyconsidered inadequate to deliver sustainableproduction intensification to meet future needs(Shaxson, 2006).

Conservation Agriculture (CA) is being increas-ingly promoted as constituting a set of principlesand practices that can make a contribution to sus-tainable production intensification (FAO, 2008;Pretty, 2008) because it addresses missing com-ponents in the intensive tillage-based standardizedseed-fertilizer-pesticide approach to agricultureintensification.

This first of two papers describes CA withinthe context of a typology of tillage practices andpresents the justification for CA as a system ofprinciples and practices capable of buildingsustainability into production systems. It then dis-cusses some of CAs major achievable benefits,and presents an overview of the uptake or adoptionof CA worldwide. A second paper (Kassam et al.,2010) presents an elaboration of some of thenecessary conditions for the spread of CA.

The underpinnings of plant production,environmental resilience andagricultural sustainability

The principles of Conservation Agriculture

The main criterion for conservation-effective agricul-tural systems is the provision of an optimum environ-ment in the root-zone to maximum possible depth.Roots are thus able to function effectively andwithout restrictions to capture plant nutrients andwater. Water thus enters the soil so that (a) plantsnever, or for the shortest time possible, suffer waterstress thatwould limit theexpressionof theirpotentialgrowth; and so that (b) residual water passes down togroundwater and stream flow, not over the surface asrunoff. Beneficial biological activity, including that ofplant roots, thus occurs in the soil where it maintainsand rebuilds soil architecture, competes with poten-tial in-soil pathogens, contributes to soil organicmatter and various grades of humus, and contributesto capture, retention, chelation and slow release ofplant nutrients. Thus, conservation-effectivenessencompasses not only conserving soil and water, butalso the biotic bases of sustainability.

The key feature of a sustainable soil ecosystem isthe biotic actions on organic matter in suitablyporous soil (Flaig et al., 1977). This means that,under CA, soils become potentially self-sustainable.In CA systems with the above attributes thereare many similarities to resilient forest floor con-ditions (Blank, 2008):

Organic materials are added both as leaf and stemresidues from above the surface and as root resi-dues beneath the surface where the soil biota areactive and carbon is accumulated in the soil.

Carbon, plant nutrients and water are recycled. Rainwater enters the soil complex readily, since

rates of infiltration (maintained by surface pro-tection and varied soil porosity) usually exceedthe rates of rainfall.

Soil organic matter is neither just a provider of plantnutrients nor just an absorber of water (Flaig et al.,1977). The combined living and non-living frac-tions together form a key part of the dynamics ofsoil formation, resilience and self-sustainability ofCA systems. In the functioning of soil as a rootingenvironment, the integrated effects of the physical,chemical and hydrological components of soil pro-ductive capacity are effectively activated by thefourth, the biological component. This variouslyprovides metabolic functions, acting on the non-living organic materials (Wood, 1995; Doran &Zeiss, 2000; Lavelle & Spain, 2001; Colemanet al., 2004; Uphoff et al., 2006) to:

Retain potential plant-nutrient ions within theirown cells, with liberation on their death, actingas one form of slow-release mechanism;mycorrhizae and rhizobia, as well as free-livingN-fixing bacteria, make nutrients available toplants in symbiotic arrangements.

Break down and transform the complexmolecules of varied dead organic matter intodifferent substances, both labile and resistant,according to the composition of the substrate.

Leave behind transformed materials with differ-ing degrees of resistance to subsequent break-down by biotic process of other soil organisms.Over the long term, this leaves some residuesless changed than others, providing long-lastingand slowly released remnant reserves of the

THE SPREAD OF CONSERVATION AGRICULTURE 293

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nutrient and carbonaceous materials of whichthey were composed.

Produce organic acids which, by leaching, contri-bute to soil formation from the surface downwardsby acting to break down mineral particles as partof the soil weathering process. Organic acidsalso help with transporting lime into the soilprofile and mobilizing nutrients like phosphates.

Provide organic molecules as transformationproducts which contribute markedly to soilsCEC; this also augments the soils bufferingcapacity to pH changes and to excesses ordeficiencies of nutrient ions available to plants.

Provide humic gums which, together with fungalhyphae and clay bonds, make for different sizesof rough-surfaced aggregates of individual soilparticles that in turn provide the permeabilityof the soil in a broad distribution of pore sizes.

Increase the burrowing activities of meso-organisms such as earthworms, and of roots(leaving tubes after they have died and beendecomposed).

The key components of optimumConservation Agriculture

The three components of optimum CA are:

(1) Maintaining year-round organic matter coverover the soil, including specially introducedcover crops and intercrops and/or the mulchprovided by retained residues from the previouscrop;

(2) Minimizing soil disturbance by tillage and thusseeding directly into untilled soil, eliminatingtillage altogether once the soil has beenbrought to good condition, and keeping soil dis-turbance from cultural operations to theminimum possible;

(3) Diversifying crop rotations, sequences andassociations, adapted to local environmentalconditions, and including appropriate nitrogen-fixing legumes; such rotations contribute tomaintaining biodiversity above and in the soil,contribute nitrogen to the soil/plant system,and help avoid build-up of pest populations.

The soil capacity to favour root growth and watertransmission is maintained through the activity of

soil organisms sufficiently provisioned with organicmatter, water and nutrients. A consequence of theiractivity is soil aggregation interspersed with voids(pores), depending on organisms production ofroots, exudates, gums, hyphae and on their prolifera-tive burrowing and distributive activities. Multipleattributes of organic matter in soil dynamized bythe soil biota therefore make it a key factor forimproving and maintaining yields (of plants and ofwater). Management actions which increase/opti-mize organic matter content of soils tend to be bene-ficial; those that result in depletion of organic mattercontent tend to be detrimental.

Tillage tends to engender accelerated oxidativebreakdown of organic matter with acceleratedrelease of increased volumes of CO2 to the atmos-phere, beyond those from normal soil respirationprocesses. Combining the retention of crop residues(rather than export or burning off) with directseeding of crops without normal tillage leads toretention and increase of organic matter, as a sub-strate for the activity of soil biota and for thesoils capacities to retain carbon, and to betterprovide water and nutrients to plant roots ondemand over sustained periods. The relationshipbetween components of CA and desired soil con-ditions are listed in Table 1 (Friedrich et al., 2009).

Tillage has long been used by farmers to loosensoil, make a seedbed and control weeds. But not alloutcomes are positive, especially when consideredover long timescales. Wheels, implements and evenfeet can compact soil. Too-frequent (and/or too-severe) tillage results in disruption of the aggregatesmaking up a soils biologically induced architecture.Since the sustainability of a soils productive capacitydepends on the influence of the soil biota on soil-crumb/aggregate re-formation, the soil aeratingeffects of undue tillage can accelerate the rate ofbiotic activity and the consequent more-rapid oxi-dation of their substrate organic matter. If themean rate of soils physical degradation exceeds themean rate of its recuperation due to the soil biota,its penetrability by water, roots and respirationgases diminishes, productivity declines, and runoffand erosion ensue. The soils which are most vulner-able to tillage-stimulated rapid loss of soil organicmatter are those of coarse texture and where theclay fraction is dominated by low-activity clays.Such soils (e.g., ferralsols, cambisols) are widely dis-tributed in the tropics and subtropics, and total over

294 A. KASSAM ET AL.


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Table 1 Effects of CA components fully applied together

CA component QTo achieve P

Mulch cover(crop residues,cover-crops,

greenmanures)

No tillage(minimal orno soil

disturbance)

Legumes (ascrops for fixingnitrogen and

supplying plantnutrients)

Crop rotation(for severalbeneficialpurposes)

Simulate forest floor conditionsp p

Reduce evaporative loss of moisture fromsoil surface

p

Reduce evaporative loss from upper soillayers

p p

Minimize oxidation of soil organic matter,CO2 loss

p

Minimize compaction by intense rainfall,passage of feet and machinery

p

Minimize temperature fluctuations at soilsurface

p

Maintain supply of organic matter assubstrate for soil biota

p

Increase and maintain nitrogen levels inroot-zone

p p p p

Increase CEC of root-zonep p p p

Maximize rain infiltration; minimize runoffp p

Minimize soil loss in runoff or windp p

Maintain natural layering of soil horizonsby actions of soil biota

p p

Minimize weedsp p p

Increase rate of biomass productionp p p p

Speed soil porosity recuperation by soilbiota

p p p p

Reduce labour inputp

Reduce fuel-energy inputp

Recycle nutrientsp p p p

Reduce pests and diseasesp

Rebuild damaged soil conditions anddynamics

p p p p

Source: Friedrich et al., 2009.



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750 million ha (FAO, 19781981; Higgins &Kassam, 1981).

A typology of terms

Tillage or conventional tillage generally refers toinversion ploughing of topsoil to at least 20 cm ormore. Several terms have been coined to reflect non-plough-based tillage practices in production systems.Some of these production systems may have soilorganic cover from crop residues of previous cropsand from cover crops, some may be based on mono-cropping, and others may include crop rotations andassociations with legumes and non-legumes includingdeep-rooting annual crops and trees.

We provide a description of different types oftillage practices and associated terms in Table 2.This typology illustrates the various tillage termsused and the relative severity of tillage associatedwith different tillage practices from the mostsevere soil disturbance in the case of TillageAgriculture (Terms 1, 1a, 1b, 1c in Table 2) toleast severe soil disturbance in the case ofConservation Agriculture (Terms 3, 3a, 3b), withConservation Tillage being somewhere in between(Terms 2, 2a, 2b). In Italy, Agricolturu Blu (orBlue Agriculture) is the term used synonymouslywith CA (Pisante, 2007), and in francophoneareas the term Direct seeded mulch-based croppingsystem (DMC) is used to describe a family ofpractices known as CA (Seguy et al., 2006a,b,2008). The term CA was adopted during the FirstWorld Congress on Conservation Agriculture,Madrid 2001 (organized by FAO and the EuropeanCA Federation: see http://www.fao.org/ag/ca).

Farmers across the world in different agro-ecological and socio-economic situations adopt arange of strategies in order to approximate to theseoptimum conditions. Therefore a typology of tillagepractices in production systems needs primarily tobe based on the methods used (Table 2) and the out-comes the practices employed have on the way soilsreact, with respect to improvement in productivityand sustainability simultaneously for the provisionof plants and water on a regular recurrent basis,which is considered in the next section.

Table 3 provides a ranking of agriculturalsystems according to effectiveness of conservationof soils capacities to yield plants and water on a

sustainable basis, based on the similarities anddifferences among practices in terms of the keycharacteristics of CA: no soil disturbance (stirring);direct seeding, permanent soil cover with plantorganic matter; crop rotations and associationsincluding legumes.

Such types of information from soils in goodcondition under CA provide a range of yardsticksagainst which to compare the benefits of CA andthe health of the soil with the damages caused byconventional tillage agriculture, as discussedbelow.

Organic agriculture, agroforestry and shiftingagriculture are included in Table 3 in addition tothe three production systems described in Table 1because CA has many features in common withthese systems, although organic farming does notpermit the use of synthetic materials such asmineral fertilizers. Where organic farming is tillage-based, application of the three CA principles andassociated practices would enhance productivityand resilience of organic production systems andoffer the economic and environmental benefits thathave been described earlier. Indeed, one futureopportunity that may be harnessed is the integrationof compatible CA practices into organic farming.CA-based organic farming would lead to greatersoil health and productivity, increased efficiency ofuse of organic matter, and reduction in use ofenergy. Organic CA farming is already practised inthe USA, Brazil and Germany.

Agroforestry systems involve the growing ofwoody perennials and annual crops together in asustainable manner in most ecologies, and it isincreasingly practised in degraded areas with peren-nial legumes. The practice brings environmentalbenefits through soil protection and efficiency ofutilization of water and soil nutrients. It alsocreates a wider diversity of environments for wild-life and other fauna. Local knowledge concerningutility of native species could be mixed with scienti-fic information to develop future agroforestryfarming systems. A particular advantage of CA inagroforestry systems is the better compatibilitywith tree and field crops since the tree rootscannot be caught by ploughs or deeper reachingtillage implements. CA works well for agroforestryand related systems in which crops are combinedwith woody perennials in the production system.This is particularly because the minimal or no soil



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Table 2 Typology of terms describing tillage practices in production systemsa

Terms Description/comments

[1] Tillage Agriculture Farming based on intensive mechanical tillage involving soil inversion andharrowing, and high soil disturbance. Conventional arable agriculture isnormally based on soil tillage as the main operation. The most widelyknown tool for this operation is the plough, which has become a symbol ofagriculture. Soil tillage has in the past been associated with increasedfertility, which originated from the mineralization of soil nutrients as aconsequence of soil tillage. This process leads in the long term to a reductionof soil organic matter through its accelerated oxidation by soil organisms. Soilorganic matter not only provides nutrients for the crop but is also, above allelse, a crucial element for the stabilization of soil structure. Therefore, mostsoils degrade under prolonged intensive arable agriculture. This structuraldegradation of the soils results in the formation of crusts and compactionand leads in the end to soil erosion. The process is dramatic under tropicalclimatic situations but can be noticed all over the world. Mechanization ofsoil tillage, allowing higher working depths and speeds and the use of certainimplements like ploughs, disk harrows and rotary cultivators, has particularlydetrimental effects on size, arrangement and stability of soil structural units/soil crumbs.

[1a] Tillage, intensive tillage,conventional tillage

Tillage is a generic term and is used broadly. Tillage embraces all soiloperations using plough, harrow and other farm tools or mechanicalimplements for seedbed preparation that aim at creating soil and environmentalconditions for seed germination, seedling establishment and crop growth. Itincludes mechanical methods based on conventional techniques of ploughingand harrowing. Intensive tillage systems leave little crop residue cover on thesoil. These types of tillage systems are often referred to as conventional tillagesystems. These systems involve often multiple operations with implements suchas a mouldboard plough, disk plough, chisel plough, rotary tiller, subsoiler,ridge or bed-forming tillers. Then a finisher with a harrow, rolling basket andcutter can be used to prepare the seedbed; there are many variations. It may betaken to include the use of hand-held tillage implements, as found on manysmallholder farms.

[1b] Plough-till Refers to mechanical soil manipulation of an entire field, and involvesmouldboard or disk ploughing followed by one or two harrowings. Plough-tillembraces primary cultivation based on ploughing with soil inversion, secondarycultivation using disks or cultivators, and tertiary working by cultivators andharrows. These tools are often drawn by animals or by tractors and othermechanically powered devices. The mechanical soil disturbance involvedincreases the risk of erosion. Ploughing removes the vegetation cover andexposes the soil to rainfall, wind and overland flow. It also encouragesaccelerated rates of oxidation of soil organic matter and consequently ofcarbon dioxide to the atmosphere. The technique gives a weed-free seedbed,incorporates fertilizer and improves soil conditions. The effects of tillagemethods on soil properties and on the erosion risk are hard to generalize.The effects vary depending on basic soil properties. For example, where thesoil has favourable structure with a high proportion of water-stableaggregates, and is permeable, mechanical soil disturbance is likely toincrease the risks of soil erosion. On the other hand, where the soil has asmooth crusted surface and compacted subsoil horizons, a massivenon-porous, unstable structure, carefully judged, timely mechanical tillageis likely to decrease the risks of soil erosion, usually only temporarily.

(Continued)



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Table 2 Continued


[1c] Minimum-till orminimum tillage

The term minimum-till has caused the greatest confusion because the minimumcultivation required to grow a crop successfully varies from zero to a complete rangeof primary and secondary tillage operations depending on soil properties andcrops. It is commonly defined as the minimum soil manipulation necessary for cropproduction or meeting tillage requirements under the existing soil and climaticconditions. It often means any system that has few tillage requirements. It may alsomean tillage of only part of the land, e.g. strip tillage or zonal tillage. It is mainly doneto reduce cost and hence it is also sometimes understood as the combination ofseveral tillage operations in one implement.

[2] ConservationTillage (CT)

The origin of CT is the attempt to reduce soil erosion. The classical definition of CT isany tillage operation which leaves a minimum of 30% of the soil surface covered withcrop residues. This results in planting or sowing through the previous crops residuesthat are purposely left on the soil surface. The primary aim of CT is to reduce tillageoperations typically associated with intercrop soil or seedbed preparation. In strip-till(see below), which is also called zone tillage or vertical tillage, a narrow band of soilis tilled and seeding is done directly into the loosened soil in this strip. In no-till, nointercrop tillage is used and seeding is done directly into the surface residues ofpreviously harvested crops. The term CT has been used for varied tillage practicesunder a range of conditions. The vague use of the term for differing situations hascreated confusion and misunderstanding. The term encompasses a broad spectrumof practices ranging from no-till to intensive tillage, depending on soil conditions. CThas been defined as any tillage sequence that reduces the loss of soil or water relativeto plough-till; often it is a form of non-inversion tillage that retains a protective layer ofmulch, and is more specifically aimed at SWC (soil and water conservation). The keytechniques used for SWC are (1) residue mulches and (2) an increase in surfaceroughness. Increases in surface roughness can be achievedby chisel ploughing, striptillage, ridge-furrow systems or tillage methods that cause soil inversion. If done at theright soil moisture content and with the right equipment, inversion tillage can producean almost ideal rough seedbed. Adequate supplies of mulching materials are notalways available. In such situations, CT techniques may include contour ridges, tiedridges, camber bed system, and broad bed-and-furrow systems. Some commonlyused practices falling under the generic term of CT include: no-till, minimum-till,reduced tillage, mulch tillage and ridge tillage, all aiming at preserving the topsoil, andsaving on fuel, labour and equipment costs. Reduced tillage is often used to describeall no-ploughbasedcultivationpractices, oftenbut not exclusivelywith soil disturbanceconfined to soil depth of less than 15 cm. Themain purpose is to leave the soil surfaceuntouched and with this even ripping or subsoiling can qualify under CT.

[2a] Strip-till Strip-till is a conservation system that uses a minimum of tillage. The term is usedto describe a system of establishing a crop that minimizes the amount of soildisturbance and maximizes efforts to retain the integrity of crop residue on thesoil surface. It combines the soil drying and warming benefits (when required) ofconventional tillage with the soil-protecting advantages of no-till by disturbing onlythe portion of the soil that is to contain the seed row. This type of tillage is performedwith special equipment and requires the farmer to make multiple trips. Each row thathas been strip-tilled is usually about 810 inches (2025 cm) wide. Another benefitof strip-tilling is that the farmer can apply chemicals and fertilizer at the same timeas tillage. Strip-till differs from no-till/direct seeding. It normally involves a tillageoperation in the autumn that clears residue in the target seed zone, places soil in aridge to aid drying and soil warmth to facilitate seeding at a later date, and may ormay not include fertilizer placement. A second operation at seeding time placesseed (and usually additional fertilizer) in the ridged seed zone.

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Table 2 Continued


[2b] No-till or No-tillage,Zero-till or Zero-tillage,No-till farming, Directseeding

These terms often mean the same and refer to growing crops from year to yearwithout disturbing the soil through tillage. When a crop is planted directly into aseedbed that has not been tilled since the previous seedbed it is called a no-till orno-tillage system. The term no-till is used interchangeably with the terms zero-till anddirect seeding and vice versa. The maximum amount of crop residue is retained onthe surface, and weeds are controlled by chemicals, by residue mulch, by using anaggressive cover crop, or by a combination of these methods. Soil-disturbingactivities are limited only to those necessary to plant seeds, place nutrients andcondition residues. Direct seeding describes a system of establishing a crop thatminimizes the amount of soil disturbance and maximizes efforts to retain theintegrity of residue on the soil surface. If soil is disturbed at harvesting, as in the caseof root crops, some workers argue the system is no longer a no-till system.According to the definition given here, however, soil disturbance at harvest isallowed in a no-till system. No-till with retained crop residues increases the amountof water in the soil, decreases erosion, and increases the amount and variety of lifein and on the soil. When repeated continuously, it can be developed into CA, sensustrictu. However, the term direct seeding is often also used for seeding intoconventionally prepared soil, contrary to transplanting small plants or even tocombining all tillage and the seeding operation in one pass with special equipment.Therefore the term direct seeding should be used in combination with no- orzero-tillage if it is referring to no-tillage.

[3] ConservationAgriculture (CA)

CA is a concept for resource-saving agricultural crop production that strives toachieve acceptable profits together with high and sustained production levelswhile concurrently conserving the environment. CA is based on enhancing naturalbiological processes above and below the ground. Interventions such asmechanical soil-disturbing tillage are reduced to an absolute minimum, and the useof external inputs such as agrochemicals and nutrients of mineral or organic originare applied at an optimum level and in a way and quantity that does not interferewith, or disrupt, the biological processes. CA is characterized by three sets ofprinciples which are linked to each other and are applied simultaneously, namely:(1) continuous minimum mechanical soil disturbance including direct seeding andno inversion tillage; (2) permanent organic soil cover with crop residue, stubble,cover crops, etc.; and (3) diversified crop rotations in the case of annual crops orplant associations in case of perennial crops. The term CA was adopted during theFirst World Congress on Conservation Agriculture, Madrid 2001, organized by FAOand the European Conservation Agriculture Federation. CA systems are alsoreferred to as No-Till or Zero-Till Farming Systems when no-tillage is accompaniedby direct planting of crop seeds, permanent organic soil cover and crop rotation asdescribed above for CA. The term is quantified as follows:(1) Minimal Soil Disturbance: the disturbed area must be less than 15 cm wide or

25% of the cropped area (whichever is lower). No periodic tillage that disturbs agreater area than the aforementioned limits.

(2) Soil cover: three categories are distinguished: 3060%, 6190% and 91%ground cover, measured immediately after the planting operation. Ground coverless than 30% will not be considered CA.

(3) Crop rotation: rotation should involve at least three different crops. However,mono-cropping is not an exclusion factor if it does not lead to pest build-upor other problems.

[3a] Agricoltura Blu (or BlueAgriculture)

This is synonymous with CA. The name Agricoltura Blu was coined by the ItalianAssociation for an Agronomical and Conservative Land Management (AIGACoS).Blue refers to water and the environmental benefits of CA.

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disturbance means that roots of trees are notdamaged by tillage, plus the system benefits fromall the other advantages of CA including theenhancement of soil health and productivity. Infact, several tree crop systems in the developingand developed regions already practise some formof CA, but these systems can be further enhancedby improved crop associations including legumes,and integration with livestock. Alley croppinghas been one innovation in this area that isbeginning to offer productivity, economic andenvironmental benefits to producers who are ableto take advantage of it (Friedrich et al., 2009;Sims et al., 2009).

Shifting agriculture, also referred to as bushfallow rotation or slash-and-burn or rotationalfarming, is based on the clearing of land toprepare a cultivation plot and subsequently aban-doning this to regrowth and eventual natural refor-estation. It is a stable form of agriculture under lowpopulation density regimes, but rising populationdensity decreases regrowth time available forforests and leads to this system becoming unsustain-able. Some shifting agriculture has evolved intosophisticated agroforestry management systemswhile in others it continues to be practised inresponse to poor land tenure policies. Shifting culti-vation can be adapted to CA, changing from slashand burn systems to slash and mulch systems. Thisway, it is possible for the communities involved toharness a greater range of ecosystem services forthemselves and for the greater society.

Benefits of Conservation Agriculture

CA represents a fundamental change to agricul-tural production systems. The main benefits aredescribed in the following sections and provide anindication why farmers are adopting CA and whyit deserves greater attention from the research anddevelopment community. However, the manysynergistic interactions between components ofCA practices are not yet fully understood. Ingeneral, scientific research on CA systems lagsbehind what farmers are discovering and adaptingon their own initiative. This is partly because CAis a complex, knowledge-intensive set of systemswhich does not lend itself to easy scrutiny by aresearch community often driven by short-termreductionist thinking and approaches (Stoop &Kassam, 2005; Uphoff et al., 2006; Kassam, 2008;Stoop et al., 2009; Uphoff & Kassam, 2009).

Conservation Agriculture as a fundamentalchange in the agricultural productionsystem

CA is a means of assuring production of plants andwater recurrently and sustainably. It does this byfavouring improvements in the condition of soilsas rooting environments. CA is not a single technol-ogy, but a range based on one or more of the threemain CA described above. CA functions bestwhen all three key features are adequately

Table 2 Continued


[3b] Direct seedingmulch-based croppingsystems (DMC)

DMC systems are described as being part of the family of practices known as CA.These systems have been developed to counteract soil degradation and to achievemore sustainable grain production. Under tropical and subtropical conditions theefficiency of such systems increases with the introduction of multifunctional covercrops growing in rotation with the main commercial crops or whenever climaticconditions are too risky for planting a commercial crop. The introduction of covercrops leads to a better utilization of available natural resources throughout the year,more biomass production, permanent soil protection and higher organic restitutionsto the soil. DMC systems also offer environmental, economic and agronomicadvantages to farmers.

aThe sequence of terms in the table is in the order of decreasing severity, corresponding to increasing effectiveness ofincorporating key elements of CA principles and practices, in line with CA definition and description, and with ranking ofagriculture systems in Table 3 according to effectiveness of conservation of soils capacities to yield plants and water on asustainable basis.



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Table 3 A means of ranking agriculture systems according to the effectiveness of conservation of soils capacities to yieldplants and water on a sustainable basis

Genericagriculturesystem atmaturefunctioning

Key characteristicsof CA ideal

Relative comparability withmature CA

>

Notes

Tillage withoutrotation

a. No soil stirring B

b. Direct seeding B

c. Permanent o.m. cover B

d. Rotations legumes B Q? Only if pasture system withlegumes

Tillage withrotation

a. No soil stirring Q? Annuals may be in rotation withperennials

b. Direct seeding B No, unless under-sowingpasture spp. into annualcrops

c. Permanent o.m. cover Q If crops in rotation with pasture,for a proportion of the time thesoil will be less exposed

d. Rotations legumes R Q? Crops themselves may includelegumes in rotation; pasturesmay include clovers and/orother legumes

Conservationtillage/Reducedtillage

a. No soil stirring Q Cropping may be in rotation,with reduced severity oftillage

b. Direct seeding Q If system in transition to CA,seeding might be withminimum-disturbance drillstowards CA ideal

c. Permanent o.m. cover Q If crops in rotation with pasture,at least for a proportion of thetime the soil will be lessexposed

d. Rotations legumes Q System may permit longerproportion of time/largerproportion of area actually with100% cover

(Continued)



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Table 3 Continued




>

Notes

Minimumtillage

a. No soil stirring Q Specific aim of reduced soildisturbance, but frequency maynot be reduced even if severityof disturbance is reduced

b. Direct seeding Q More likely to tend towardsCA-type drill

c. Permanent o.m. cover Q Higher proportion of cropresidues remain, and greaterproportion of time/area likely tobe covered

d. Rotations legumes Q? Closer approximation to CAlikely

Conservationagriculture

a. No soil stirring B Ideal CA, as yardstick

b. Direct seeding B Ideal CA, as yardstick

c. Permanent o.m. cover B Ideal CA, as yardstick

d. Rotations legumes B Ideal CA, as yardstick

Organicagriculture

a. No soil stirring Q? Does not necessarily involvereduction in tillage

b. Direct seeding Q? Organic often in a tillagesystem, whose severity orfrequency may/may notfavour movement towardsCA ideal

c. Permanent o.m. cover Q? Organic often in tillage system,whose severity may/may notfavour movement towards CAideal of 100% cover

d. Rotations legumes Q Organic systems generallyfavour rotations and legumesin system

# Two other types of system may/can show certain positive attributes of CA #

(Continued)



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Table 3 Continued




>

Notes

Shiftingagriculture

a. No soil stirring R $ Q Sometimes severe, but ideallyfor one or few seasons only,within very long (decades-long)rotations with interveningtumble-down/bush fallowyears for soil recuperation.Annual crop yields low butoverall sustainable in systemsnot pressured by populationincrease and without externalinputs

b. Direct seeding Q . . . . . . . . . . . . . . . . . . . . .Q Possibly, of favoured spp.seeded through litter etc. ofperennial bush shrubs etc., atdifferent stages of long rotation

c. Permanent o.m. cover Q............... Q

. . . . . . . . .

Increasing as bush-fallowvegetation thickens. But, underpressure of rising ruralpopulation, time forrecuperation under bush-fallow,before reopening for tillage,becomes shorter andless effective

d. Rotations legumes Q Q Maybe of annuals in tillageyears; regrowth bushvegetation may includeleguminous species in overalllong-term bush rotation

Agroforestry a. No soil stirring R ?Q Depends on proportions of area frequency of planting ofannual/biennial/perennial cropsin chosen system, and onwhether arrangement ofpreferred spp. on land surface isintermixed, vertically layered,alleys, etc.

b. Direct seeding Q Likely/often according to layout,timing, etc.

c. Permanent o.m. cover Q Likely for long periods and overa significant proportion of area

d. Rotations legumes R ?Q Possible, in annual and/orperennial areas of layout



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combined together in the field. It is significantlydifferent from conventional tillage agriculture(Hobbs, 2007; Shaxson et al., 2008). Ideally itavoids tillage once already damaged soil has beenbrought to good physical condition prior to initiat-ing the CA system; maintains a mulch cover oforganic matter on the soil surface at all times, forproviding both protection to the surface and sub-strate for the organisms beneath; specifically usessequences of different crops and cover-crops inmulti-year rotations; and relies on nitrogen-fixinglegumes to provide a significant proportion of N(Boddey et al., 2006).

CA also relies on liberating other plant nutrientsthrough biological transformations of organicmatter. This can be augmented as necessary by suit-able mineral fertilizers in cases of specific nutrientdeficiencies, but organic matter also providesmicronutrients that may not be available from thebag (Flaig et al., 1977). CA can retain and mimicthe soils original desirable characteristics (forestfloor conditions) on land being first opened foragricultural use. Throughout the transformationto agricultural production CA can sustain thehealth of long-opened land which is already ingood condition, and it can regenerate that in poorcondition (Doran & Zeiss, 2000). CA is a powerfultool for promoting soil and thus agriculturalsustainability.

These multiple effects of CA when appliedtogether are illustrated in Table 1 (Friedrich et al.,2009). In contrast with tillage agriculture, CA canreverse the loss of organic matter, improve andmaintain soil porosity and thus prolong the avail-ability of plant-available soil water in times ofdrought (Derpsch et al., 1991; Stewart, 2007; Maz-vimavi & Twomlow, 2008). It can also reduceweed, insect pest and disease incidence by biologicalmeans, raise agro-ecological diversity, favour bio-logical nitrogen fixation, and result in both raisedand better stabilized yields accompanied bylowered costs of production (Blackshaw et al.,2007; Mariki & Owenya, 2007; Gan et al., 2008).Furthermore, CA can be explored for the purposeof achieving some of the objectives of the Inter-national Conventions on combating desertification,loss of biodiversity, and climate change (Beniteset al., 2002).

It is important to recognize that the improve-ments seen at macro-scale (e.g. yields, erosion

avoidance, water supplies and farm profitability),are underlain and driven by essential features andprocesses happening at micro-scale in the soilitself. FAO (2008) indicates that:

widespread adoption of CA has been demon-strated to be capable of producing large anddemonstrable savings in machinery and energyuse, and in carbon emissions, a rise in soilorganic matter content and biotic activity, lesserosion, increased crop-water availability andthus resilience to drought, improved recharge ofaquifers and reduced impact of the apparentlyincreased volatility in weather associated withclimate change. It will cut production costs, leadto more reliable harvests and reduce risksespecially for small landholders.

Higher stable yields and incomes from CA

As an effect of CA, the productive potential of soilrises because of improved interactions between thefour factors of productivity: (a) physical: bettercharacteristics of porosity for root growth, move-ment of water and root-respiration gases; (b) chemi-cal: raised CEC gives better capture, release ofinherent and applied nutrients: greater control/release of nutrients; (c) biological: more organisms,organic matter and its transformation products; (d)hydrological: more water available.

The combination of the above features to raiseproductive potential makes the soil a better environ-ment for the development and functioning of cropplants roots. Improvements in the soils porosityhave two effects: a greater proportion of the incidentrainfall enters into the soil; and the better distributionof pore-spaces of optimum sizes results in a greaterproportion of the received water being held atplant-available tensions. Either or both togethermean that, after the onset of a rainless period, theplants can continue growth towards harvest forlonger than would previously been the case before the plant-available soil water is exhausted.In addition, increased quantities of soil organicmatter result in improved availability, and durationof their release into the soil water, of needed plantnutrients both those within the organic matterand those from off-farm. Thus the availability ofboth water and plant nutrients is extended together.Under these conditions, plants have a better



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environment in which to express their genetic poten-tials, whether they have been genetically engineeredor not. Yield differences have been reported in therange of 20120 per cent between CA systems andtillage systems in Latin America, Africa and Asia(Derpsch et al., 1991; Pretty et al., 2006; Landers,2007; Ernstein et al., 2008; FAO, 2008; Hengxinet al., 2008; Rockstrom et al., 2009). In Paraguay,small farmers have been able to successfully growcrops that initially were thought not to be appropri-ate for no-till systems, such as cassava. Plantingcassava under CA in combination with cover cropshas resulted in substantial yield increases, sometimesdouble the yields compared to conventional farmingsystems (Derpsch & Friedrich, 2009).

FAO (2001a) have indicated that:

machinery and fuel costs are the most importantcost item for larger producers and so the impactof CA on these expenditure items is critical.Most analyses suggest that CA reduces themachinery costs. Zero or minimum tillage meansthat farmers can use a smaller tractor and makefewer passes over the field. This also results in alower fuel and repair costs. However, this simpleview masks some complexities in making a faircomparison. For example, farmers may see CAas a complement to rather than as a full substitutefor their existing practices. If they only partiallyswitch to CA (some fields or in some years), thentheir machinery costs may rise as they must nowprovide for two cultivation systems, or they maysimply use their existing machinery inefficientlyin their CA fields.

No-till, or a reduced proportion of the area needingtillage (e.g. planting basins or zai/tassa), requiresless input of energy per unit area, per unit output,and lower depreciation rates of equipment. Overtime, less fertilizer is required for the same output(Lafond et al., 2008). Production costs are thuslower, thereby increasing profit margins as well aslessening emissions from tractor fuel (Hengxinet al., 2008). Better soil protection by mulch coverminimizes both runoff volumes and the scouringof topsoil, carrying with it seeds and fertilizers.Such losses represent unnecessary cost, wasted rain-water and wasted energy. Their avoidance increasesthe margin between profits and costs, which for-merly, under tillage agriculture, were accepted asnormal expenses to be anticipated.

CA systems are less vulnerable to insect pests,diseases and drought effects because better soiland plant conditions include also greater bioticdiversity of potential predators on pests and dis-eases, while crop rotations break insect pest build-ups. Here, much of the cost of avoiding or con-trolling significant pest attacks is diminishedbecause of it being undertaken by healthierplants, breaks in pest life cycles and natural preda-tors (Settle & Whitten, 2000; Evers & Agostini,2001; Blank, 2008). Research conducted byKliewer et al., (1998) in Paraguay and Sorrensenand Montoya (1984) in Brazil has shown thatcrop rotation and short-term green manure covercrops can reduce the cost of herbicides drastically,due to reduction in weed infestation over time(Blackshaw et al., 2007). While many still thinkthat green manure cover crops are economicallynot viable, farmers in Brazil and Paraguay havelearned that the economics of CA can be substan-tially increased with their use (Derpsch et al.,1991; Derpsch, 2008a).

As a result, the financial benefits for farmers inLatin America who have adopted CA have beenstriking (Landers, 2007). However, these take timeto fully materialize. Sorrenson (1997) compared thefinancial profitability of CA on 18 medium- andlarge-sized farms with conventional practice in tworegions of Paraguay over 10 years. By year 10, netfarm income had risen on CA farms fromUSD10,000 to over USD30,000, while on conven-tional farms net farm income fell. Medium- andlarge-scale CA farmers had experienced:

Less soil erosion, improvements in soil structureand an increase in organic matter content, cropyields and cropping intensities.

Reduced time between harvesting and sowingcrops, allowing more crops to be grown over a12-month period.

Decreased tractor hours, farm labour, machinerycosts, fertilizer, insecticide, fungicide and herbi-cide, and cost savings from reduced contour ter-racing and replanting of crops following heavyrains.

Lower risks on a whole-farm basis of higher andmore stable yields and diversification into cashcrop (FAO, 2001b).



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Such effects are cumulative over space, and canaccumulate over time from degraded condition toimproved stabilized condition, with yields andincome rising over time, as in this example oflarge-scale wheat production under CA in Kazakh-stan. Figure 1 shows the development of wheatyields and financial benefits after changing fromconventional tillage to no-till agriculture onmechanized farms in northern Kazakhstan. Theinternal rate of return to investment (IRR) is 28per cent (Fileccia, 2008). Thus, farmers shouldturn away from the struggle to reach the highestyield. Instead they should aim for the best economicyield. Figure 1 indicates that CA can achieve thisgoal even under the relatively marginal conditionsprevailing in northern Kazakhstan.

Further, in Paraguay, yields under conventionaltillage declined 515 per cent over a period of 10years, while yields from zero-till CA systemsincreased 515 per cent. Over the same period,fertilizer and herbicide inputs dropped by anaverage of 3050 per cent in the CA systems(Derpsch, 2008a). In Brazil, over a 17-yearperiod, maize and soybean yields increased by 86and 56 per cent respectively, while fertilizerinputs for these crops fell by 30 and 50 per centrespectively. In addition, soil erosion in Brazildecreased from 3.48.0 t/ha under conventionaltillage to 0.4 t/ha under no-till, and water lossfell from approximately 990 to 170 t/ha(Derpsch, 2008a).

Climate change adaptation and reducedvulnerability

Reduced vulnerability to effects of drought, lesserosion, and lesser extremes of soil temperaturesrepresent a managed adaptation of CA systems toclimate change effects such as, for example, moreintense rainstorms, increased daily ranges of temp-eratures, and more severe periods of drought.Overall, CA systems have a higher adaptability toclimate change because of the higher effective rain-fall due to higher infiltration and thereforeminimum flooding and soil erosion as well asgreater soil moisture-holding capacity.

The advantage of CA over tillage agriculture interms of the greater soil moisture-holding capacityand therefore duration of plant-available soil moist-ure is illustrated by Derpsch et al. (1991), who showthat soil moisture conditions in rooting zonesthrough growing seasons under CA are better thanunder both minimum and conventional tillage.Thus crops under CA systems can continuetowards maturity for longer than those under con-ventional tillage. In addition, the period in whichavailable nutrients can be taken up by plants isextended, increasing the efficiency of use. Thegreater volume and longer duration of soil moist-ures availability to plants (between the soils fieldcapacity and wilting point) has significant positiveoutcomes both for farming stability and profit-ability. The range of pore sizes which achieves this

Figure 1 Financial benefits of Conservation Agriculture in wheat production in Northern Kazakhstan (IRR28 per cent)



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also implies the presence of larger pores which con-tribute to through-flow of incident rainwater downto the groundwater (Shaxson et al., 2008).

Infiltration rates under well managed CA aremuch higher over extended periods due to bettersoil porosity. In Brazil (Landers, 2007), a 6-folddifference was measured between infiltration ratesunder CA (120 mm per hour) and traditionaltillage (20 mm per hour). CA thus provides ameans to maximize effective rainfall and rechargegroundwater as well as reduce risks of flooding.Due to improved growing season moisture regimeand soil storage of water and nutrients, cropsunder CA require less fertilizer and pesticides tofeed and protect the crop, thus leading to a loweringof potential contamination of soil, water, foodand feed. In addition, in soils of good porosity,anoxic zones hardly have time to form in the rootzone, thus avoiding problems of the reduction ofnitrate to nitrite ions in the soil solution (Flaiget al., 1977).

Good mulch cover provides buffering of temp-eratures at the soil surface which otherwise arecapable of harming plant tissue at the soil/atmos-phere interface, thus minimizing a potential causeof limitation of yields. By protecting the soilsurface from direct impact by high-energy rain-drops, it prevents surface-sealing and thus main-tains the soils infiltration capacity, while at thesame time minimizing soil evaporation.

In the continental regions of Europe, Russia andNorth America, where much annual precipitationis in the form of snow in the winter, CA provides away of trapping snow evenly on the field whichmay otherwise blow away, and also permits snowto melt evenly into the soil. In the semi-arid areas ofcontinental Eurasia, one-third or more of the precipi-tation is not effectively used in tillage systems, forcingfarmers to leave land fallow to conserve soil moist-ure, leading to extensive wind erosion of topsoil fromfallow land, and to dust emissions and transport overlarge distances (Brimili, 2008). Under CA, more soilmoisture can be conserved than when leaving theland fallow, thus allowing for the introduction ofadditional crops including legume cover crops intothe system (Blackshaw et al., 2007; Gan et al.,2008). In the tropics and subtropics, similar evidenceof adaptability to rainfall variability has beenreported (Ernstein et al., 2008; Rockstrom et al.,2009).

Reduced greenhouse gas emissions

No-till farming also reduces the unnecessarily rapidoxidation of soil organic matter to CO2 which isinduced by tillage (Reicosky, 2008; Nelson et al.,2009). Together with the addition of mulch as aresult of saving crop residues in situ as well asthrough root exudation of carbon compoundsdirectly into the soil during crop growth (Jones,2007), there is a reversal from net loss to net gainof carbon in the soil, and the commencementof long-term processes of carbon sequestration(West & Post, 2002; Blanco-Canqui & Lal, 2008;CTIC/FAO, 2008).

Making use of crop residues and the direct rhizo-spheric exudation of carbon into the soil representsthe retention of much of the atmospheric C cap-tured by the plants and retained above the ground.Some becomes transformed to soil organic matterof which part is resistant to quick breakdown(though still with useful attributes in soil), and rep-resents net C-accumulation in soil, eventuallyleading to C-sequestration. Tillage, however,results in rapid oxidation to CO2 and loss to theatmosphere. Expanded across a wide area, CA hasthe potential to slow/reverse the rate of emissionsof CO2 and other greenhouse gases by agriculture.

Studies in southern Brazil show an increase incarbon in the soil under CA. According to Testaet al. (1992), soil carbon content increased by 47per cent in the maizelablab system, and by 116per cent in the maizecastor bean system, com-pared to the fallowmaize cropping system whichwas taken as a reference. Although exceptionshave been reported, generally there is an increasein soil carbon content under CA systems, asshown by the analysis of global coverage by Westand Post (2002). In systems where nitrogen wasapplied as a fertilizer, the carbon contents increasedeven more. Baker et al. (2007) found that croprotation systems in CA accumulated about 11 t/haof carbon after 9 years. Under tillage agricultureand with monoculture systems the carbon liber-ation into the atmosphere was about 1.8 t/ha peryear of CO2 (FAO, 2001b).

With CA, reduced use of tractors and otherpowered farm equipment results in lower emissions.Up to 70 per cent in fuel savings have been reported(FAO, 2008). CA systems can also help reduce theemissions for other relevant greenhouse gases,



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such as methane and nitrous oxides, if combinedwith other complementary techniques. Bothmethane and nitrous oxide emissions result frompoorly aerated soils, for example from permanentlyflooded rice paddies, from severely compacted soils,or from heavy poorly drained soils. CA improvesthe internal drainage of soils and the aeration andavoids anaerobic areas in the soil profile, so longas soil compactions through heavy machinerytraffic are avoided and the irrigation water manage-ment is adequate.

The soil is a dominant source of atmosphericN2O (Houghton et al., 1997). In most agriculturalsoils biogenic formation of nitrous oxide isenhanced by an increase in available mineral Nwhich, in turn, increases the rates of aerobicmicrobial nitrification of ammonia into nitratesand anaerobic microbial reduction (denitrification)of nitrate to gaseous forms of nitrogen (Bouwman,1990; Granli & Bckman, 1994). The rate of pro-duction and emission of N2O depends primarilyon the availability of a mineral N source, the sub-strate for nitrification or denitrification, on soiltemperature, soil water content, and (when denitri-fication is the main process) the availability of labileorganic compounds. These variables are universaland apply to cool temperate and also warm tropicalecosystems. Addition of fertilizer N, therefore,directly results in extra N2O formation as an inter-mediate in the reaction sequence of both processeswhich leaks from microbial cells into the atmos-phere (Firestone & Davidson, 1989). In addition,mineral N inputs may lead to indirect formationof N2O after N leaching or runoff, or followinggaseous losses and consecutive deposition of N2Oand ammonia. CA generally reduces the need formineral N by 3050 per cent, and enhances nitro-gen factor productivity. Also, nitrogen leachingand nitrogen runoff are minimal under CAsystems. Thus overall, CA has the potential tolower N2O emissions (e.g., Parkin & Kaspar,2006), and mitigate other GHG emissions asreported by Robertson et al. (2000) for themid-west USA and Metay et al. (2007) for theCerrado in Brazil. However, the potential for suchresults applying generally to the moist and coolUK conditions has been challenged, for example,by Bhogal et al. (2007) and questions have beenraised over their validity due to the depth of soilsampled, particularly for N2O emissions and the

overall balance of GHG emissions (expressed on acarbon dioxide (CO2-C) equivalent basis).

Better ecosystem functioning and services

Societies everywhere benefit from the many resourcesand processes supplied by nature. Collectively theseare known as ecosystem services (MEA, 2005), andinclude clean drinking water, edible and non-ediblebiological products, and processes that decomposeand transform organic matter. Five categories of ser-vices are recognized: provisioning services such as theproduction of food, water, carbon and rawmaterials; regulating, such as the control of climate,soil erosion and pests and disease; supporting, suchas nutrient and hydrological cycles, soil formationand crop pollination; cultural, such as spiritual andrecreational benefits; and preserving, which includesguarding against uncertainty through the mainten-ance of biodiversity and sanctuaries.

CAs benefits to ecosystem services, particularlythose related to provisioning, regulating and sup-porting, derive from improved soil conditionsin the soil volume used by plant roots. The improve-ment in the porosity of the soil is effected by theactions of the soil biota which are present ingreater abundance in the soil under CA. Themulch on the surface protects against the compact-ing and erosive effects of heavy rain, damps downtemperature fluctuations, and provides energy andnutrients to the organisms below the soil surface.When the effects are reproduced across farms in acontiguous micro-catchment within a landscape,the ecosystem services provided such as cleanwater, sequestration of carbon, avoidance oferosion and runoff become more apparent. Thebenefits of more water infiltrating into the groundbeyond the depth of plant roots is perceptible interms of more regular streamflow from ground-water through the year, and/or more reliableyields of water from wells and boreholes (e.g.,Evers & Agostini, 2001). The benefits of carboncapture become apparent in terms of the darkeningcolour and more crumbly feel of the soil,accompanied by improvements in crop growth,plus less erosion and hence less deposition of sedi-ment downstream in streambeds.

Legumes in CA rotations provide increased in situavailability of nitrogen, thus diminishing the needfor large amounts of applied nitrogenous fertilizers



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(Boddey et al., 2006). Also, there is increasing evi-dence of a significant amount of liquid carbonbeing deposited into the soil through root exudationinto the rhizosphere (Jones, 2007).

Society gains from CA on both large and smallfarms by diminished erosion and runoff, less down-stream sedimentation and flood damage to infra-structure, better recharge of groundwater, moreregular streamflow throughout the year with theless frequent drying up of wells and boreholes,cleaner civic water supplies with reduced costs oftreatment for urban/domestic use, increased stab-ility of food supplies due to greater resilience ofcrops in the face of climatic drought, and betternutrition and health of rural populations, with lesscall on curative health services (ICEPA/SC, 1999;World Bank, 2000; Pieri et al., 2002).

In CA systems, the sequences and rotations ofcrops encourage agrobiodiversity as each crop willattract different overlapping spectra of micro-organisms. The optimization of populations,range of species and effects of the soil-inhabitingbiota is encouraged by the recycling of crop residuesand other organic matter which provides the sub-strate for their metabolism. Rotations of cropsinhibit the build-up of weeds, insect pests andpathogens by interrupting their life cycles, makingthem more vulnerable to natural predator species,and contributing development-inhibiting allelo-chemicals. The same crop mixtures, sequences androtations provide above-ground mixed habitatsfor insects, mammals and birds.

The adoption of ConservationAgriculture

Global area and regional distribution

Although much of the CA development to date hasbeen associated with rain-fed arable crops, farmerscan apply the same principles to increase the sus-tainability of irrigated systems, including those insemi-arid areas. CA systems can also be tailoredfor orchard and vine crops with the direct sowingof field crops, cover crops and pastures beneath orbetween rows, giving permanent cover andimproved soil aeration and biodiversity. Thecommon constraint, according to farmers, to prac-tising this latter type of intercropping is competition

for soil water between trees and crops. However,careful selection of deep-rooting tree species andshallow-rooting annuals resolves this. FunctionalCA systems do not replace but should be integratedwith current good land husbandry practices(Shaxson, 2006).

Because of the benefits that CA systems generatein terms of yield, sustainability of land use, incomes,timeliness of cropping practices, ease of farmingand ecosystem services, the area under CA systemshas been growing rapidly, largely as a result of theinitiative of farmers and their organizations(Figure 2). It is estimated that, worldwide, thereare now some 106 million ha of arable cropsgrown each year without tillage in CA systems.Table 4 provides information on country-specificarable and permanent cropland area under CA,and as percentage of total arable and permanentcropland area.

A useful overview of the adoption of CA in indi-vidual countries is given by Derpsch and Friedrich(2009). Except in a few countries (USA, Canada,Australia, Brazil, Argentina, Paraguay, Uruguay,Kazakhstan, China, Kenya, Tanzania, Lesotho,Malawi, South Africa), these approaches to sustain-able farming have not been mainstreamed in agri-cultural development programmes or backed bysuitable policies and institutional support. Conse-quently, the total area under CA is still small(about 7 per cent) relative to areas farmed usingtillage. Nonetheless, the rate of increase globallysince 1990 has been at the rate of some 5.3 mil-lion ha per annum, mainly in North and SouthAmerica and in Australia and New Zealand.

Currently, South America has the largest areaunder CA with 49,586,900 ha (46.6 per cent oftotal global area under CA) followed by NorthAmerica (39,981,000 ha, 37.5 per cent). Australiaand New Zealand have 12,162,000 ha (11.4 percent), Asia 2,630,000 ha (2.3 per cent), Europe1,536,100 ha (1.4 per cent) and Africa 470,100 ha(0.4 per cent).

Area of CA in industrialized countries

No-till agriculture in the modern sense originated inthe USA in the 1950s, and from then until 2007 theUSA had the largest area under no-till worldwide. Inthe USA, no-till currently accounts for some 25.5per cent of all cropland. Conventional agriculture



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with tillage remains in the majority even if CA is avalid option for farmers, as compared withsouthern Latin America where no-till has becomethe majority agricultural system with 60 per centof the cropland area. According to CTIC (2005),only half of the total area under no-till in the USAis being permanently not tilled, some 26.5 millionha, corresponding to 15.3 per cent of total arableand permanent cropland. This occasional tillageprevents the system from reaching its optimumbalance, as the soil is disturbed from time to time.Research has shown that it takes more than 20years of continuous no-till to reap the full benefitsof CA. Farmers who practise rotational tillage(plough or till their soils occasionally) will notexperience the full benefits of the system (Derpsch,2005).

In Canada, CA is now practised on some13.5 million ha (25.9 per cent of arable and per-manent crop area), although the no-till technologyis used over a much larger area, 46.1 per cent ofcropland (Derpsch & Friedrich, 2009). In Austra-lia, CA has been widely embraced by farmers (12million ha). It has improved weed control, timeof sowing, given drought tolerance and hasenabled dry regions to use water most efficiently(Crabtree, 2004; Flower et al., 2008). But inap-propriate seeding machines which move themulch too much, and sheep that graze crop resi-dues are leading to an insufficient soil cover.

New Zealand has about 160,000 ha under CA,which corresponds to 17 per cent of all croplandarea. New Zealand farmers were among the firstto use and develop the no-till technology: in the1970s, pasture renovation without tillage wastried and practised successfully. Later, annualcrops were seeded with the no-till. However, themajority of the increase in CA area has occurredsince 2000.

CA is not widespread in Europe (Basch et al.,2008; Lahmar, 2009): no-till systems do notexceed 2 per cent of the agricultural cropland.Since 1999 ECAF (European Conservation Agricul-ture Federation) has been promoting CA in Europe,and adoption is visible in Spain, France, Germany,Ukraine and Finland, with some farmers at proofof concept stage in the UK, Ireland, Portugal, Swit-zerland and Italy.

Area of CA in developing countries

Brazil has the longest experience in CA, and nowhas 25.5 million ha under various forms of CA.Since its first appearance in 1972, many usefullessons have originated from Brazil and from neigh-bouring Argentina and Paraguay, which now haverespectively 19.7 and 2.4 million ha of CA. Theyhave also set important precedents for the engage-ment of farmers as principal actors in the develop-ment and adaptation of new technologies.

Figure 2 Development of Conservation Agriculture over the last 20 years by world region in total area (ha) and as averagepercentage across the adopting countries of the respective region (from FAO, 2008)



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Table 4 Conservation Agriculture adoption by country over the past 30 years (in 1000 ha) and in percentage of total arableand permanent cropland area for 20082009

Country 19731977

19781982

19831987

19881992

19931997

19982002

20032007

20082009

CA % of 20082009 crop area

Argentina 2 6 500 3,950 15,001 19,719 19,719 58.8

Australia 100 100 400 400 9,000 12,000 26.9

Bolivia 240 706 706 18.4

Brazil 57 232 650 1,350 8,847 18,744 25,502 25,502 38.3

Canada 1,951 4,592 8,823 13,481 13,481 25.9

Chile 120 180 10.3

China 100 1,330 0.9

Colombia 102 102 2.9

Finland 200 8.8

France 50 50 50 50 150 200 10.2

Germany 354 354 2.9

Hungary 8 8 0.2

Ireland 0.1 0.1 ,0.1

Italy 80 80 0.8

Kazakhstan 600 1,300 5.7

Kenya 15 33.1 0.6

Lesotho 0.13 0.13 ,0.1

Mexico 22.8 22.8 0.1

Morocco 4 ,0.1

Mozambique 9 9 0.2

Netherlands 2 2 5

New Zealand 75 75 75 75 63.2 63.2 162 162 17.4

Paraguay 200 1,200 2,094 2,400 54.5

Portugal 25 25 1.5

Slovakia 10 10 0.7

(Continued)



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Brazil took the initiative when herbicides (para-quat and diquat) and direct-drilling equipmentbecame available in the USA, and it became clearthat conventional ploughing was leading to a severeenvironmental and economic crisis for farmers insouthern Brazil. Progressive and wealthy farmersled the way, some travelling to the USA to learnabout their soil conservation and managementsystems and to purchase direct-drilling equipment.Common interest groups were then formed amonglarge-scale farmers and then by small-scale farmers.CA has emerged mainly as a result of farmer inno-vation together with problem-solving support frominput supply companies, state and federal researchand extension organizations, universities, as well aslong-term funding commitments from internationaldonors such as the World Bank and GTZ.However, the momentum for innovation and adop-tion still is with farmers and their organizations.

Apart from enabling their land to be croppedmore intensively without risk of degradation, CA

attracted Brazilian farmers because it increasedcrop yields (at least 1025 per cent), greatlyreduced surface runoff and soil erosion, and cuttractor use, resulting in big savings in fuel and pro-duction costs. Such benefits explain why today,Latin American farmers practise zero-tillage CAon a continuous basis on some 50 million ha.

Paraguay has experienced a continuous andsteady growth of CA adoption, almost all of itover the past 10 years. Tillage practices have dis-appeared almost completely. In tractor mechan-ized farming systems, about 90 per cent(2.4 million ha in 2008) of all crop area is underCA (Derpsch & Friedrich, 2009). Similarly, insmall farmer production systems with animal trac-tion or manual systems, no-till practices haveincreased to about 30,000 ha covering 22,000small farmers. The increased interest in smallfarmer CA systems has been a result of govern-ment support that provides grants for buyingno-till equipment.

Table 4 Continued

Country 19731977

19781982

19831987

19881992

19931997

19982002

20032007

20082009

CA % of 20082009 crop area

SouthAfrica

1 1 300 368 2.4

Spain 300 650 3.7

Sudan 10 ,0.1

Switzerland 9 9 2.1

Tunisia 0.03 6 6 0.1

Ukraine 100 0.3

UK 200 275 275 24 24 0.4

USA 2,200 2,200 4,800 6,839 17,361 22,400 26,500 26,500 15.3

Uruguay 338 554 655.1 47.4

Venezuela 300 300 9.0

Zambia 40 40 0.8

Zimbabwe 15 0.4

TOTAL 2,685 2,661 6,261 11,440 35,013 66,849.03 100,253.03 106,505.23 6.9

Source: FAO AQUASTAT, 2009; http://www.fao.org/ag/ca; FAO STAT, 2009.



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In Bolivia CA practices increased in the last 10years, especially in the lowlands in the east of thecountry where the main crop is soybeans whosearea has increased from around 240,000 ha in theyear 2000 to 706,000 ha in the year 2007(Derpsch & Freidrich, 2009). The occurrence ofwind erosion in conventional tillage systems hasbeen one of the major driving forces for adoption.Also the increased water use efficiency underno-till system is valued by farmers in a region withlow and erratic rainfall.

Uruguay has also seen a significant increase inpermanent no-till practices, with some 47 per centof its arable and permanent cropland switching toCA systems in the last 10 years. Some 65 per centof arable crops are seeded on rented land forwhich contracts are renewed every year, and thishinders the planning of medium-term crop rotationand investment strategies. In Uruguay the inte-gration of crops with livestock is very popular andCA systems fit well into the requirements forcroplivestock production systems. Pastures aregrown for several years until they show signs ofdegradation. Crops are then grown for severalyears according to the needs of the farmers andthe market situation. Venezuela, Chile, Colombiaand Mexico have modest amounts of their landunder no-till systems, ranging from some23,000 ha in Mexico to 300,000 ha in Venezuela(Derpsch & Friedrich, 2009).

The main crops grown under CA in Latin Americainclude soybean, maize, wheat, sunflower, canola aswell as cassava, potato and a number of horticulturaland cover crops. CA practices are also being appliedto perennial crops and to tree crops. Soil cover isachieved by growing cash crops and cover cropseither in association or sequentially. Main covercrops include oats, oilseed-radish, rye, lupin, vetch,Mucuna (velvet bean), Dolichos and Cajanus(pigeon pea). In some cases, especially amongsmall-scale farmers, herbicide use can be reducedby direct-drilling the seed into a cover crop that hasbeen flattened using a knife roller. Specializedno-till equipment has been developed in Brazil andthe Americas, including tractor-mounted, animaldrawn and hand tools (including jab planters).These are being exported to Africa and Asia andbeing adapted there for local use and manufacture.

Asian and African countries have seen uptake ofCA in the past 1015 years. In Central Asia, a fast

development of CA can be observed in the last 5years in Kazakhstan and the neighbouring Russianareas. Kazakhstan now has 3.5 million ha underreduced tillage, mostly in the northern drier pro-vinces, and of this 1.3 million ha (5.7 per cent ofcrop area) are real CA with permanent no-tilland rotation. This puts Kazakhstan among the topten countries with the largest cropland area underCA systems. CA has had a rapid development inrecent years as a result of farmers interest, accumu-lated research knowledge, facilitating governmentpolicies and an active input supply sector(Derpsch & Friedrich, 2009). China too hasequally a dynamic development of CA. It began10 years ago with research, then the adoptionincreased during the last few years and the technol-ogy has been extended to the rice productionsystem. Now more than 1.3 million ha are underCA in China and 3,000 ha in DPR Korea wherethe introduction of CA has made it possible togrow two successive crops (rice, maize or soya assummer crop, winter wheat or spring barley aswinter crop) within the same year, through directdrilling of the second crop into the stubble of thefirst. The feasibility of growing potatoes underzero tillage has also been demonstrated in DPRKorea (FAO, 2007).

In the Indo-Gangetic plains across India, Paki-stan, Nepal and Bangladesh, in the wheatricecropping system, there is large adoption of no-tillwheat with some 5 million ha, but only marginaladoption of permanent no-till systems and full CA(Hobbs et al., 2008). This is because virtually allrice is grown under some form of tillage system. InIndia, the adoption of no-till practices by farmershas occurred mainly in the wheatrice double crop-ping system and has been adopted primarily for thewheat crop. The main reason for this has been thattillage takes too much time resulting in delayedseeding and yield loss of the wheat crop after rice(Hobbs & Gupta, 2003; Hobbs et al., 2008). TheRiceWheat Consortium for the Indo-GangeticPlains, an initiative of CGIAR, led by IRRI andCIMMYT and involving several National Agricul-tural Research Centres, has been promoting no-tillpractice and it is mainly their efforts that haveresulted in the massive uptake of no-till wheat inthe region (Ernstein et al., 2008). The uptake ofthe technology was rapid in the northwesternstates which are relatively better endowed with



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respect to irrigation, mechanization and where thesize of holdings is relatively large (34 ha) com-pared to the eastern region which is less equippedand mechanized and where the average landholding is small (1 ha) (Derpsch & Friedrich, 2009).

Among the most encouraging research experi-ences has been the CA work developed in the dryMediterranean environments of North Africa inMorocco (Mrabet, 2007, 2008) and Tunisia (Ben-Hammouda et al., 2007) where highly innovativeadaptations have been made to the low and unpre-dictable rainfall. In sub-Saharan Africa, innovativeparticipatory approaches are being used todevelop supply chains for producing CA equipmenttargeted at smallholders. Similarly, participatorylearning approaches such as those based on theprinciples of farmer field schools (FFS) are beingencouraged to strengthen farmers understandingof the principles underlying CA and how these canbe adapted to local situations. The correspondingprogrammes recognize the need to adapt systemsto the very varied agro-ecosystems of the regions,to the extreme shortage of land faced by manyfarmers and to the competing demands for cropresidues for livestock and fuel problems that areparticularly pronounced amongst small-scalefarmers in Africa in the semi-arid tropical and Med-iterranean regions.

CA is now beginning to spread to the sub-SaharanAfrica region, particularly in eastern and southernAfrica, where it is being promoted by FAO,CIRAD, the African Conservation TillageNetwork, ICRAF, CIMMYT, ICRISAT, IITA(Haggblade & Tembo, 2003; Baudron et al., 2007;Boshen et al., 2007; Kaumbutho & Kienzle, 2007;Nyende et al., 2007; SARD, 2007; Shetto &Owenya, 2007; Ernstein et al., 2008). Building onindigenous and scientific knowledge and equipmentdesign from Latin America, farmers in at least 14African countries are now using CA (in Kenya,Uganda, Tanzania, Sudan, Swaziland, Lesotho,Malawi, Madagascar, Mozambique, South Africa,Zambia, Zimbabwe, Ghana and Burkina Faso). CAhas also been incorporated into the regional agricul-tural policies by NEPAD (New Partnership forAfricas Development) and more recently by AGRA(Alliance for a Green Revolution in Africa). In thespecific context of Africa (where the majority offarmers are resource-poor and rely on less than1 ha), CA systems are relevant for addressing the

old as well as new challenges of climate change,high energy costs, environmental degradation andlabour shortages. In Africa CA is expected to increasefood production while reducing negative effects onthe environment and energy costs, and result in thedevelopment of locally adapted technologies consist-ent with CA principles (FAO, 2008).

While large numbers of small-scale farmers (inParaguay, China and various African countries)have adopted CA practices, experience indicatesthat the spread tends to be at a slower pace thanamong larger-scale farmers. With food securityamong their major objectives, many small-scalefarmers are hesitant to invest scarce labour, land,seed and fertilizer in cover crops that do not resultin something to eat or to sell. They also sufferfrom restricted access to relevant knowledge aswell as to inputs or credit. As a result, there is anincreasing recognition of the need to encouragefarmers to move towards full adoption of CA attheir own pace, testing out promising approachesinitially on small areas of their farms and progress-ively expanding as their confidence in the resultsdevelops. However, because of these constraints,some researchers (e.g., Gowing & Palmer 2008;Giller et al., 2009) have suggested that either theevidence for the case for CA is not adequate orthat under present circumstances CA is inappropri-ate for the majority of resource-constrained small-holder farmers and farming systems in Africa(Giller et al., 2009). The global evidence of CAadoption presented in this paper and elsewhere(Fowler & Rockstrom, 2001; Haggblade &Tembo, 2003; FAO, 2008) suggests that elementscan work for small farmers.

Global distribution of CA across climatezones

CA is practised in all climate zones of the worldwhere annual and perennial crops can be grown,from the tropics and subtropics to the temperateregions (FAO, 2008). Functional examples exist inthe tropics and subtropics (summer rainfall), inthe moist (subhumid) and dry savannah and thehumid forest environments in Latin America (e.g.,Brazil, Colombia, Venezuela, Argentina, Bolivia,Chile, Mexico, Paraguay, Uruguay), sub-SaharanAfrica (e.g., Kenya, Tanzania, Zimbabwe,


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Conservation Agriculture Spread Justification, Sustainability and Uptake