Review: Redesigning Canadian prairie cropping systems for … · Review: Redesigning Canadian...

Review: Redesigning Canadian prairie cropping systemsfor profitability, sustainability, and resilience

Joanne R. Thiessen Martens1, Martin H. Entz1, and Mark D. Wonneck2

1Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2(e-mail: [email protected]); and 2Science and Technology Branch,

Agriculture and Agri-Food Canada, Calgary, Alberta, Canada T2P 0T8.Received 7 May 2014, accepted 24 July 2015. Published on the web 10 August 2015.

Thiessen Martens, J. R., Entz, M. H. and Wonneck, M. D. 2015. Review: Redesigning Canadian prairie cropping systems for

profitability, sustainability, and resilience. Can. J. Plant Sci. 95: 1049�1072. Redesign of agricultural systems according toecological principles has been proposed for the development of sustainable systems. We review a wide variety of ecologicallybased crop production practices, including crop varieties and genetic diversity, crop selection and rotation, cover crops,annual polyculture, perennial forages, perennial grains, agroforestry systems, reducing tillage, use of animal manures andgreen manures, soil biological fertility, organic production systems, integrated crop�livestock systems, and purposefuldesign of farm landscapes (farmscaping), and discuss their potential role in enhancing the profitability, environmentalsustainability, and resilience of Canadian prairie cropping systems. Farming systems that most closely mimic naturalsystems through appropriate integration of diverse components, within a context of supportive social and economicstructures, appear to offer the greatest potential benefits, while creating a framework in which to place all other farmingpractices. Our understanding of ecological relationships within agricultural systems is currently lacking, and a major shiftin research, education, and policy will be required to purposefully and proactively redesign Canadian prairie agriculturalsystems for long-term sustainability.

Key words: Ecological agriculture, Canadian prairies, profitability, resilience, farming systems, sustainable agriculture

Thiessen Martens, J. R., Entz, M. H. et Wonneck, M. D. 2015. Repenser les systemes de culture des Prairies canadiennes enfonction de la rentabilite, de la durabilite et de la resilience : tour d’horizon. Can. J. Plant Sci. 95: 1049�1072. Pour voir sedevelopper des systemes durables, d’aucuns ont propose qu’on repense les systemes agricoles selon les principes de l’ecologie.Les auteurs examinent une batterie de pratiques agricoles misant sur l’ecologie, notamment le recours a la diversite varietaleet genetique, la selection des cultures et l’assolement, les cultures-abris, la polyculture annuelle, les fourrages et les cerealesvivaces, l’agroforesterie, le travail minimum du sol, l’usage de fumier et d’engrais verts, la fertilisation biologiquedu sol, l’agriculture biologique, les systemes integrant les productions vegetales et animales, et l’amenagement des paysagesagricoles. Ils parlent du role que de telles pratiques pourraient jouer en rehaussant la rentabilite, la perenniteenvironnementale et la resilience des systemes de culture dans les Prairies canadiennes. Les systemes agricoles qui imitentle mieux la nature par une integration judicieuse de divers elements, avec l’appui de structures socioeconomiques adequates,semblent offrir les plus grands avantages eventuels, tout en instaurant un cadre dans lequel s’insereront toutes les autrespratiques agricoles. Nous manquons presentement de connaissances sur les liens qui unissent l’ecologie aux systemesagricoles, et des changements majeurs devront etre apportes au niveau de la recherche, de l’education et des politiques si l’onveut remodeler sciemment et de facon proactive les systemes agricoles des Prairies canadiennes afin d’en garantir la durabilitea long terme.

Mots cles: Agriculture ecologique, Prairies canadiennes, rentabilite, resilience, systemes agricoles, agriculture durable

The long-term sustainability of the Canadian agriculturesector depends on its ability to thrive economically whileprotecting our natural resource base and building resi-lience to stresses and shocks. Modern agricultural sys-tems prevalent on the Canadian prairies, while oftenhighly productive, are associated with a number ofenvironmental and social issues that threaten the sustain-ability of the sector, including rising energy and inputcosts, greenhouse gas (GHG) emissions, loss of biodiver-sity, soil andwater degradation, corporate concentration,global competition in production of bulk commodities,and a steady reduction in the number of farms (Morrisonand Kraft 1994; Rude and Fulton 2001; Hoeppner et al.

2005; Pimentel et al. 2005; Pretty 2008; Eilers et al.2010; Halberg 2012; Kremen and Miles 2012; Malezieux2012).

Many of these issues stem from reliance on simplifiedproduction systems consisting mainly of annual mono-cultures. Monoculture production systems compromisebiodiversity, utilize resources inefficiently, and are sus-ceptible to pest outbreaks (Morrison and Kraft 1994;Altieri 1999; Phelan 2009). Continuous production ofannual crops requires constant disturbance (either

Abbreviations: BNF, biological nitrogen fixation; GHG,greenhouse gas; NGP, Northern Great Plains

Can. J. Plant Sci. (2015) 95: 1049�1072 doi:10.4141/CJPS-2014-173 1049

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mechanical or chemical) to maintain the system in theearliest successional state (Thomas and Kevan 1993;Phelan 2009). Despite being a net nutrient exporter(Morrison and Kraft 1994), nutrient pollution in agri-cultural systems is a problem owing to altered nutrientcycles and poor fertilizer use efficiency (Janzen et al.2003; Drinkwater and Snapp 2007). Uncoupling of cropand livestock production has exacerbated the problem(Russelle et al. 2007). Based on these observations,Phelan (2009) noted that modern agricultural systemsshare the characteristics of dysfunctional or highlystressed ecosystems.

Gliessman (2010) argues that improvements in effi-ciency of input use and input substitution (e.g., herbicidesinstead of tillage) are not enough to address the challengesfacing modern agriculture. Instead, he argues that farm-ing systems must be redesigned based on a new setof ecological relationships. In other words, agriculturalsystems require systemic change. This review seeks tohighlight and evaluate the cropping practices and systemsthat might make up these redesigned prairie farmingsystems. Key focus areas include diversified crop produc-tion systems, reduced tillage, nutrient cycling throughendogenous input systems, integration of crops andlivestock, and the purposeful design of farm landscapes(farmscaping); evaluation criteria relate to profitability,environmental sustainability, and resilience. Sources con-sidered in this review include reports and peer-reviewedpublications from the Canadian prairie and NorthernGreat Plains (NGP) regions, where available, relevantstudies from other regions, and a few personal commu-nications where published information is scarce.

DEFINING AND ASSESSING PROFITABILITY,SUSTAINABILITY AND RESILIENCE

IN CROPPING SYSTEMSA wide range of approaches has been developed toevaluate the potential value of alternative agriculturalpractices, including both ecological and social compo-nents (e.g., Xu and Mage 2001; Darnhofer et al. 2010b;Cabell and Oelofse 2012). While assessment approachesdiffer, common themes of profitability, sound environ-mental practice (sustainability), and resilience (bothecological and social), recur throughout the literature.For the purposes of this analysis, we have identified apotential set of criteria in each of these theme areas, asoutlined below and in Table 1. Despite the difficulty indefining appropriate criteria (Darnhofer et al. 2010b;Cabell and Oelofse 2012; Koohafkan et al. 2012), theiruse here is both to emphasize the need for acceptedcriteria and to highlight the potential of alternativesystems and practices to be better than the dominantindustrial agricultural model.

Environmental Sustainability‘‘Systems high in sustainability can be taken as those thataim to make the best use of environmental goods andservices while not damaging these assets’’ (Pretty 2008).

Sustainable agriculture practices are based on biologicaland ecological processes, principally the interactionsbetween soils, crops, and animals (Pretty 2008; Malezieux2012). Such systems protect natural capital, minimizenutrient losses and use of non-renewable inputs, includerecycling and feedback mechanisms, make optimal use ofecological niches, and include high levels of biodiversity,while continuing to be productive (Pretty 2008; Phelan2009; Koohafkan et al. 2012). Accordingly, key environ-mental criteria by which to assess these systems centrearound soil health, reduced soil erosion risk, effective soilwater management, water and air quality protection,effective nutrient management, natural pollination andpest and disease suppression services, GHG emissions,and carbon (C) sequestration (Table 1).

ProfitabilityProfitability refers to the capacity of an enterprise togenerate more revenue through the sale of its productsthan it costs to produce those products. Profitabilitycan be enhanced by increasing production, obtaining ahigher price for products, or by reducing costs. Majoroperating costs in prairie cropping systems includepurchased inputs (fertilizers and pesticides), seed, fuel,and labour; thus, any reduction in these inputs whilemaintaining yield and quality increases profitability.

Profitable market positions may be secured over thelong term by developing protectable advantages, whereproducts, processes, knowledge, relationships, and/orconditions are both profitable and difficult for rivalsto imitate (Porter 1996). For example, the combinationof favourable local growing conditions for a specificproduct matched with tacit knowledge of productiontechniques for those conditions can create a relativelysecure and stable market opportunity. Direct marketingof specialized products to niche markets can also createopportunities for protectable advantages.

Table 1. Sustainability, profitability, and resilience assessment criteria of

relevance to Canadian prairie cropping systems

Sustainability criteria Profitability criteria Resilience criteria

Soil health Reduced input costs Resilience to climateextremes

Reduced soil erosion Increased production Reduced energy useDewatering wet soils Premium prices Reduced use of external

inputsStoring water in dry soils Protectable advantages Enterprise diversityWater quality protection Income stability Agroecological integrityAir quality protection Reduced financial risk Adaptive capacity /

flexibilityEcological nutrient managementNatural pollination servicesNatural pest suppression servicesNatural disease resistanceReduced greenhouse gas emissionsCarbon storage/sequestration

1050 CANADIAN JOURNAL OF PLANT SCIENCE

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Alongwith year-to-year profitability, riskmanagementand income stability over years also become important forthe long-term economic success of farms (Table 1).

ResilienceResilience refers to the ability of a system to undergochange while still retaining control of its structure andfunction (Cabell and Oelofse 2012). Heterogeneity inspace and time, as well as functional and response diver-sity, are key components of both ecological and socialresilience. Resilience also requires a certain tensionbetween adaptability and efficiency (Darnhofer 2010a);redundancies within the system and apparent sub-functional diversity may be associated with lowershort-term productivity but also provide greater capacityto recover from shocks (Lin 2011; MacDougall et al.2013).

Farmers play an important role in developing resi-lience, not only through their farming practices, but alsothrough their ability to learn and adapt. Darnhofer et al.(2010a) identify three elements that affect adaptivecapacity: the ability of the farm manager to learn, theflexibility of a system (both its operation and strategicflexibility), and its diversity.

Important indicators of resilience in agriculturalsystems include the ability to adapt to climate extremes,minimal dependence on external inputs such as non-renewable energy sources, enterprise diversity, agroeco-system integrity, and the flexibility of the system (Table 1).

CROP MANAGEMENT PRACTICES AND SYSTEMSTHAT HOLD POTENTIAL FOR THE CROPPING

SYSTEMS OF THE CANADIAN PRAIRIES

Diversified Crop Production SystemsDiversification of cropping systems can be achievedthrough a wide variety of farming practices that pur-posefully include agricultural diversity in both time andspace (Altieri 1999; Kremen and Miles 2012). Thesepractices have the common goal of adding variability inagroecosystem structure and function in areas such asresource use and resistance to pests. Such planned on-farm diversity attracts additional natural biodiversity,further enhancing the integrity of the agroecosystem(Altieri and Nicholls 2008; Liebman and Schulte 2015).

Crop Varieties and Genetic Diversity

Variety Selection. Crop variety selection is based onadaptation to local soil and climatic conditions, yield,ease of management, disease resistance, and end-usequality parameters (e.g., Manitoba Agriculture, Foodand Rural Development 2015). Variety selection mayalso enhance genetic diversity in cropping systems. Forexample, an Alberta study showed that rotation betweenthree barley (Hordeum vulgare L.) varieties reduceddisease incidence and enhanced barley yield and kernelsize compared with growing the same variety every year;

however, rotating to a different cereal crop speciesprovided even greater benefits (Turkington et al. 2005).

The suitability of crop varieties for low-input, ecolo-gically based production systems may be impacted bythe crop breeding environment (Drinkwater and Snapp2007). Breeders in both Manitoba and Alberta havefound that spring wheat (Triticum aestivum L.) linesselected under organic management outyielded conven-tionally selected lines when all were grown under orga-nic management, and concluded that targeted cropbreeding programmes for organic varieties would bebeneficial (Reid et al. 2011; Kirk et al. 2012). Similareffects have been observed in other crops such as lentil(Lens culinaris Medik.; Vlachostergios et al. 2011).

Heritage or historical crop varieties have receivedsignificant popular attention. Among the few studiesthat compare the productivity of heritage versus modernspring wheat cultivars, results are inconsistent (Wanget al. 2002). However, some ecological differences havebeen observed: rhizospere communities differ betweenmodern and heritage varieties of wheat (Germida andSiciliano 2001) and mycorrhizal colonization has beenobserved to be greater in older varieties than modernvarieties, which may have implications for nutrient acqui-sition in conditions of lower fertility (Hetrick et al.1992).

Cultivar Mixtures. Growing mixtures of more than onecrop cultivar may be an option for increasing geneticdiversity without a large increase in crop managementcomplexity. Intraspecific genetic diversity may play alarger role in ecological interactions than expected:Cook-Patton et al. (2010) found that increasing diversitythrough variety mixtures resulted in the same level ofincrease in primary plant productivity as through speciesmixtures but a smaller increase in arthropod diversity.

According to meta-analysis on wheat and barleycultivar mixtures, crop yields in mixtures tend to begreater than in monocultures (Kiær et al. 2009). Evenwhere yield is not increased, cultivar mixtures maycontribute to yield stability (Mengistu et al. 2010) andenhanced yield in otherwise lower-yielding cultivars(Pridham et al. 2007).

The maintenance of grain yield and quality in cultivarmixtures is primarily a result of the disease suppressionelicited by genetically diverse cultivars in the mixtures(Mundt 2002). Cultivar mixtures have been used suc-cessfully to reduce yield losses from leaf disease in springbarley crops in Europe as well as in spring wheat cropsin the United States and Germany (Manthey andFehrmann 1993; Newton 1997); others have found nobenefit to blending cultivars (Dai et al. 2012). A meta-analysis of studies on the effect of spring wheat cultivarmixtures on stripe rust indicated that cultivar mixtureshad lower disease incidence in 83% of cases, with anaverage disease incidence reduction of 28% (Huanget al. 2012).

THIESSEN MARTENS ET AL. * REDESIGNING CANADIAN PRAIRIE CROPPING SYSTEMS 1051

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Mixing resistant and susceptible cultivars may alsobe used as a strategy to slow or avoid the breakdownof disease (Bing et al. 2011) or insect (Beres et al. 2009;Fox et al. 2010) resistance in crops. However, growinga multi-line oat (Avena sativa L.) variety has beenobserved to select for complex pathogen races thatovercome resistance in all lines (Carson 2009).

Additional processes that may contribute to higheryield of mixtures over monoculture include competitionand compensation between the cultivars in the mixture(Finckh and Mundt 1992) or complementary use ofresources and divergent niches (Gallandt et al. 2001).Greater diversity in the weed suppression capability ofcultivar mixture components appears to contribute tohigher yields (Kiær et al. 2009). Wheat cultivars mayalso vary in other traits, such as mineral concentration,leading some researchers to suggest that specific cultivarmixtures could be designed to attain specific nutritionalprofiles along with high yield (Murphy et al. 2011).

Crop Selection and Crop RotationCrop selection and crop rotation have potential toenhance sustainability, profitability, and resilience withincropping systems. Choosing crops that are locallyadapted and/or adapted to a wide range of conditionsprovides a level of resilience to extreme weather condi-tions. For example, many crops grown in the Canadianprairies have flowering dates and life cycles that allowthem to tolerate cool temperatures and moisture-deficitstress (Bueckert and Clarke 2013). Further, character-istics such as associated microbial communities, plantand root architecture, and composition of residues androot exudates vary widely between plant species, pro-viding functional diversity that supports ecosystemprocesses such as nutrient cycling and soil building(Drinkwater and Snapp 2007).

Annual cropping systems can be diversified by extend-ing crop selection over temporal and spatial scales. Croprotation is widely recognized as a useful tool for weed,disease, and insect management, as well as soil healthand nutrient management, and the positive effects ofvarying crop sequences on crop yields are well docu-mented (e.g., Arshad et al. 2002; Campbell et al. 2011;Davis et al. 2012). Strategic inclusion of diverse speciesthat encompass a wide range of functional groups helpsto create cropping systems that effectively supportkey ecological processes (Altieri 1999; Entz et al. 2002;Drinkwater and Snapp 2007; Lin 2011).

Diversified crop rotations have been observed toincrease overall yield, provide more stable profits overtime, and reduce input requirements (Smith et al. 2008;Davis et al. 2012). They also have reduced potential fornitrate leaching (Malhi et al. 2009) and tend to be moreefficient in their energy use and produce lower levelsof GHG emissions (Zentner et al. 2011b). Includinglegumes in rotation may have a relatively large impacton GHG emissions and energy use due to biological

nitrogen (N) fixation (BNF) and the accompanyingreduction in N fertilizer requirements (Asgedom andKebreab 2011).

Cover CropsA cover crop is any crop grown for the purpose ofprotecting and/or improving the soil, rather than forharvest of a product. More specific goals of cover cropsmay include BNF, weed or pest suppression, preventionof soil erosion, or others. As such, cover crops haveconsiderable potential to increase the functional diversityand environmental sustainability of cropping systems(Drinkwater and Snapp 2007). Choosing a cover cropspecies and a method for including it in the croppingsystem requires careful examination of the spatial andtemporal niches available in a cropping system (ThiessenMartens and Entz 2001; Snapp et al. 2005).

Interseeding and Relay Crop Systems for Cover Crops.Growing an understory crop or cover crop together orstaggered with a cash crop may fill a spatial or temporalniche in an annual cropping system. Interseeding orrelay cropping is a common approach to successfullyestablishing and gaining the benefits of a cover crop inregions with shorter growing seasons, and has received acertain amount of attention in the NGP (e.g. Bruulsemaand Christie 1987; Thiessen Martens et al. 2001; Blaseret al. 2011).

Crop productivity and cover crop benefits in inter-seeded systems depend on resource use dynamics in thecover cropping system as well as any effects on thefollowing crop. In cover crop systems using spring-seededmixtures of cash crops and annual or perennial foragelegumes [berseem clover (Trifolium alexandrinum L.),annual medics (Medicago spp.), red clover (Trifoliumpratense L.) or hairy vetch (Vicia villosa Roth)], inter-seeded legumes added N to the system, had variableeffects on weed biomass, and increased the yield of thefollowing crop in some cases (Moynihan et al. 1996;Sheaffer et al. 2001, 2002; Pridham and Entz 2008).Effects on the yield of the interseeded cash crop werevariable, depending in part on seeding rates, soil texture,andmoisture conditions. Achieving the optimum balanceof cash and cover crops in interseeded cover crop systemswill require testing of promising combinations undervarious conditions.

Relay cropping systems may allow for more controlover resource competition between the cash crop and thecover crop and better use of moisture and heat resourcesthroughout the growing season. Many locations acrossthe southern prairies receive enough growing degreedays after winter wheat harvest to produce a cover crop;however, southern Manitoba may be the only regionthat consistently receives enough late-season moisture(Thiessen Martens and Entz 2001). In regions receivinginconsistent late-season precipitation, late-season covercrops could be used opportunistically.


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In Manitoba, red clover and alfalfa (Medicago sativaL.) were successfully established as spring-seeded relaycrops in fall-seeded winter cereals (Thiessen Martenset al. 2001; Martens et al. 2005; Cicek et al. 2014a).In Alberta, red clover, alfalfa, and winter pea (Pisumsativum L.) were established successfully with wintercereals in both fall and spring plantings (Blackshawet al. 2010). In all these studies, biomass production bycover crops varied widely, ranging from near 0 to over4000 kg ha�1. Yield benefits to the subsequent cropwere observed in all studies in treatments where legumesestablished and grew successfully. Blackshaw et al. (2010)also observed weed suppression by the alfalfa cover crop.

Late-season cover crops can have an impact on soilmoisture and microclimate. Studies in Manitoba andAlberta have reported reduced soil moisture followingproductive cover crops (Thiessen Martens et al. 2001;Kahimba et al. 2008; Blackshaw et al. 2010). Soil waterdepletion by the cover crop can be a detriment in dryclimates and a benefit in wet climates. Moderation ofnear-surface air and soil temperature has also beenobserved in cover crop systems, with implications fordepth of frost, snowmelt infiltration, and potentiallynutrient cycling and pest cycles (Thiessen Martens et al.2001; Kahimba et al. 2008).

Harvesting the main crop as forage rather than grainallows for adaptation of the legume interseeding systemto shorter growing season areas. Berseem clover inter-cropped with various cereals in northern Alberta pro-duced an average of 12.5 Mg ha�1 of total growingseason biomass, with 2.1 to 3.4 Mg ha�1 obtained fromregrowth of berseem clover after cereal forage harvest(Ross et al. 2004).

Double Cropping Systems for Cover Crops. Double crop-ping, which involves producing a second crop after theharvest of the first crop, offers another opportunity toutilize the late-season heat and moisture resources aftercash crop harvest. Early-harvested crops, such as wintercereals or annual forages, can provide a window ofopportunity for double cropping with cover crops in theCanadian prairies (Thiessen Martens and Entz 2001).

Establishment of the second crop after main cropharvest can be challenging due to extremely variableprecipitation during this period (Thiessen Martens andEntz 2001). Researchers in southern Manitoba havesuccessfully established double crops after winter cerealsover several years of research. However, biomass pro-duction of these crops has been extremely variable,ranging from 95 to 2357 kg ha�1 for double-croppedblack lentil, hairy vetch, and field pea; biomass produc-tion exceeded 1000 kg ha�1 in only a few instances(Thiessen Martens et al. 2001; Cicek et al. 2014a).

Self-regenerating Cover Crops. A deterrent to implement-ing cover cropping systems is the cost and uncertainty ofestablishing cover crops. Self-regenerating cover crops,

which reseed themselves, have the potential to addressthis issue. Adaptations of the ley farming system ofAustralia, where self-regenerating subterranean clover(Trifolium subterraneum L.) and annual medic are grownin pasture-grain systems (Grace et al. 1995), are beingexplored in both fallow-based and continuous grainproduction systems, with and without livestock, in theNGP (Carr et al. 2005a, b; May et al. 2010).

Annual medics, especially black medic (Medicagolupulina L.), and birdsfoot trefoil (Lotus corniculatus L.),can regenerate successfully from the seedbank in theNGP and have potential as self-regenerating cover cropsin this region (Sims et al. 1985; Sims and Slinkard 1991;Braul 2004; Carr et al. 2005a, b; May et al. 2010). InNorth Dakota, annual medic species established in acontinuous grain production system in 1991 were stillregenerating 8 yr later and provided significant forage forlate-season grazing and weed suppression while produ-cing enough seed to successfully re-establish themselveseach year (K. Aldridge, NDSU extension agent, Sheridancounty, ND, personal communication).

Biomass production of self-regenerating cover cropsin annual cropping systems studies varied widely, rang-ing from near 0 to over 3000 kg ha�1 in North Dakotaand Saskatchewan (Carr et al. 2005b; May et al. 2010).Available soil moisture appeared to be the main factoraffecting biomass production in both studies.

Effects of self-regenerating legumes on crop yield vary.In long-term field trials in Montana, wheat yield was1300 kg ha�1 greater in a system with ‘George’ blackmedic grown during the fallow phase of rotation than ina standard fallow-based rotation (Sims et al. 1985). Carret al. (2005b), in North Dakota, reported yield reduc-tions in systems with self-seeding forage legumes in somecases, due to soil water depletion, while in other casesthere was no effect on yield. At Indian Head, SK, Mayet al. (2010) found that after several years of includingblack medic in annual crop rotations, crop yields wereincreased by up to 57%, but only where fertilizer wasapplied at 20% of the recommended rate, suggesting thatmedics may provide the greatest benefit in organic andlow-input crop production systems.

Forage quality characteristics of black medic are equalor superior to those of alfalfa and red clover (Carr et al.2005a). Grazing ruminant livestock may promote in-creased legume reseeding by removing crop residue whilesimultaneously burying legume seeds through hoofaction (Carr et al. 2005b).

Screening of self-regenerating legumes for local adap-tation in central Manitoba (Entz et al. 2007), Wyoming(Walsh et al. 2001), andMinnesota (De Haan et al. 2002)has failed to identify a particular species or genotype thatwould satisfy all the requirements of a self-regeneratingcover crop system, but has indicated that desirablecharacteristics were present in the screened germplasmand that these qualities could be further developed.


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Cover Crops for Weed Suppression. Cover crops grownspecifically for weed suppression are often referred to assmother crops or living or killed mulches. These covercrops function by creating a physical barrier to weedgrowth and/or through allelopathic effects. Fall rye(Secale cereale L.) is known to have allelopathic effectson certain weed species but not on large-seeded cropseeds such as edible beans (Phaseolus vulgaris L.; Floodand Entz 2009). In Alberta, a short-duration fall ryecover crop during the fallow phase of rotation sup-pressed weeds and offered soil protection, while main-taining subsequent crop yields (Moyer et al. 2000).Killed mulch systems for field scale cropping using acrimper-roller are under investigation in various loca-tions in North America (e.g., Davis 2010; Mischler et al.2010; Vaisman et al. 2011).

Green Manures/Annual Forages. In regions where heatand/or moisture resources are limiting, the benefits ofcover crops may be realized by producing annualforages or green manure crops during the main growingseason. Along with the benefits typically associated withcover crops, producing annual green manures or foragesoffers an opportunity to apply a level of managementdiversity that is not typically available in annual cashcropping systems. For instance, crop choice and seedingdate can be adjusted to allow for strategic weed controloperations (mechanical or chemical) before and/or aftercover crop growth. Early harvest or incorporation ofbiomass can prevent weed seed return.

Annual forage legumes can typically produce 2 to 6Mg ha�1 of biomass under rainfed conditions on theCanadian prairies, with some reports of over 10Mg ha�1

(Bullied et al. 2002; McCartney and Fraser 2010; Entzet al., unpublished data). Both cool- and warm-seasonannual cereals grown for forage canproduce typical yieldsof 3 to 8 Mg ha�1 and can provide mid- to late-seasongrazing, either as a standing crop or in swath (May et al.2007; McCartney et al. 2008, 2009; Lenssen et al. 2010).Mixtures of annual cereals and legumes can produce largeamounts of high-quality forage biomass (Carr et al. 1998,2004; Strydhorst et al. 2008).

McCartney and Fraser (2010) have described indetail the potential role of annual forage legumes inCanada and conclude that, despite growing recognitionof their benefits, it remains challenging to find a nichefor these crops due to economic barriers. Grazinggreen manures and annual forages, rather than soil-incorporating them or harvesting them as green feed orsilage, may offer some economic benefits as well as theecological benefits of integrating livestock directly intoannual cropping systems (Thiessen Martens and Entz2011), though only limited research has been conductedin this region (McCartney et al. 2009; McCartney andFraser 2010).

Annual PolycultureGrain intercropping or annual polyculture, in whichmore than one crop is harvested for seed, offers anotheroption for increasing diversity within annual croppingsystems. There is limited documented research work ongrain intercropping in the NGP and the results of thisresearch are inconsistent. Overyielding and greater yieldstability have been observed in some crop combinationsand under some conditions, but not in others (Carret al. 1995, 2004; Szumigalski and van Acker 2005; Kautet al. 2008; Pridham and Entz 2008; Hummel et al. 2009;Nelson et al. 2012).

In spite of a lack of clear evidence for increased yield,many studies report other benefits such as weed suppres-sion (Carr et al. 1995; Szumigalski and van Acker 2005;Pridham and Entz 2008; Nelson et al. 2012), lower levelsof plant disease (Vilich-Meller 1992; Jensen et al. 2005;Pridham and Entz 2008; Hummel et al. 2009), enhancednutrient cycling (Szumigalski and van Acker 2006),and enhanced seed quality (Hummel et al. 2009). Positiveeffects of intercropping on insect populations have notbeen observed in research from the prairie region (Weisset al. 1994; Butts et al. 2003; Hummel et al. 2009).

The benefits of intercropping may also be realized innon-grain crops such as cover crops, green manures,and annual forages. These types of polycultures may offera more accessible opportunity to take advantage of thebenefits of intercropping, as harvest processes are nomorecomplex than for monocrops. Cover crop mixtures havebeen observed to bemore productive than individual covercrop species grown alone (Wortman et al. 2012). Annualforages that are grazed or harvested as hay or silage canbe grown as mixtures very successfully, while improvingforage quality and productivity (Carr et al. 1998).

Perennial Crops in RotationPerennial crops are important in developing sustainableand resilient cropping systems because of their constantsoil cover, efficient resource use, promotion of beneficialorganisms, benefits to water quality and quantity, Csequestration, and reduced GHG emissions (Pretty 2008;Asgedom and Kebreab 2011; Asbjornsen et al. 2014).While forages are the most common perennial cropin the Canadian prairies, perennial grain crops are alsobeing developed.

Perennial Forages. Perennial crops are rotated withannual crops on 5�15% of arable land in the NGP region(Entz et al. 2002). The benefits of perennial forages inrotation are well documented (Entz et al. 2002; Olmsteadand Brummer 2008). A key benefit of perennial forages inrotation is yield of annual rotation crops. In a long-termstudy in northern Alberta, wheat yields after forage were66�114% percent greater than continuous wheat for 8 yrafter forage termination (Hoyt 1990). Farmers havealso observed yield increases due to forages in rotation,with 71% reporting enhanced grain yields after forages


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compared with annual crop rotations in a survey ofManitoba and Saskatchewan forage producers (Entzet al. 1995).

Perennial forages, especially legumes, can have amajorimpact on soil nutrient status. N contributions by analfalfa hay crop in southern Manitoba were 84, 148, and137 kg N ha�1 in the first, second, and third years ofthe stand, respectively (Kelner et al. 1997). Even short-duration stands (1�2 yr) can provide significant yieldincreases in subsequent crops (Kelner and Vessey 1995;Bullied et al. 2002). However, forage legumes also removelarge quantities of nutrients from the soil, especially inhay systems. Phosphorus depletion can occur within arelatively short time frame, especially under organicmanagement, where nutrients are not replaced; however,returning livestock manure to the system can close thenutrient cycle and prevent depletion of soil nutrients(Welsh et al. 2009). Harvesting forage by grazing insteadof haying would automatically cycle most of the nutrientswithin the system (Sigua et al. 2006), without the cost ofremoving hay and applying manure.

The effects of perennial forages on other rotation cropsalso include non-nutrient factors. Perennial foragescontribute to enhanced soil health and pest suppression,both of which can provide benefits to subsequent crops(Entz et al. 2002 and references therein; Olmstead andBrummer 2008; Meiss et al. 2010). Moisture availabilityis a major determinant of forage-related benefits, sincemoisture depletion by perennial forages can reduce yieldof subsequent crops in dry regions (Entz et al. 2002);however, no-till establishment and termination of per-ennial forage stands can allow their successful integrationin more arid regions of the prairies (Jefferson et al. 2007).Water use by forages can be beneficial for dewateringsoils in regions with excess moisture and for salinitymanagement (Entz et al. 2002).

The environmental benefits of perennial forages arewell documented. Their deep root systems are able toretrieve nutrients from subsoil, thus reducing nitrateleaching, and can sequester C deep in the profile (Entzet al. 2002; Olmstead and Brummer 2008; Malhi et al.2009). Perennial forages also provide habitat for wild-life, in particular nesting birds and pollinators (Jeffersonet al. 1999; Carvell et al. 2006; Arnold et al. 2007).

Economic benefits of including perennial forages inrotation include lower input costs and reduced incomevariability, along with enhanced crop yields as discussedabove (Entz et al. 2002). The length of the forage standis key to determining its economic value; some havenoted that a 4�5 yr stand is optimal (Jeffrey et al. 1993).

Perennial Grains. A novel approach to growing harvest-able grains in an ecologically sustainable manner isperennial grain crops. Perennial grains have the poten-tial to be high yielding and economically viable, sincethey use resources more efficiently and may be grown onland that is less suited to annual cropping (Glover et al.

2010). They also have considerable potential to addressmany of the environmental concerns associated withannual agriculture by reducing tillage, offering continualsoil cover, enhancing soil health, increasing nutrientand water use efficiency, reducing GHG emissions, andproviding wildlife habitat (Pimentel et al. 2012).

Researchers at the Land Institute in Kansas have beenworking at developing perennial grain crops for manyyears and others around the world have joined the effort(Glover et al. 2010; Pimentel et al. 2012; Batello et al.2014). So far, the main crop of focus has been wheat,with efforts also being devoted to sorghum (Sorghumspp.), sunflower (Helianthus spp.), rice (Oryza spp.), rye,maize, and others (Pimentel et al. 2012). Recent evalua-tions of perennial cereal lines in Australia and theUnited States indicate that progress has been made indeveloping cereals with both a perennial habit andadequate seed production (Hayes et al. 2012; Jaikumaret al. 2012). These authors also noted a high degree ofvariability in seed quality characteristics such as size andhardness, morphological characteristics such as tillernumber and height, and grain yield, indicating consider-able potential to select for specific desirable traits.

Lower yields in perennial grains developed so far tendto be due to lower harvest index (i.e., proportion ofgrain to total biomass) and lower kernel weights thanin annual grain crops (Jaikumar et al. 2012). Continuedbreeding efforts are expected to narrow these gaps.Lower yields may also be offset economically by reducedinput costs, as fertilizer and pesticide requirements areexpected to be lower due to better resource use efficiencyand pest resistance (Pimentel et al. 2012). Perennialwheat may only need to yield 65% of annual wheat tomake it economically feasible, or only 40% of annualwheat if perennial wheat could produce both forage forlivestock and grain (Bell et al. 2008).

Perennial grain research in Manitoba and Albertacurrently focuses on intermediate wheatgrass [Thino-pyrum intermedium (Host) Barkworth & D.R.Dewey],sunflower (Helianthus maximilliani Schrad), and peren-nial cereal rye (Doug Cattani, University of Manitoba,personal communication; Jamie Larsen, Agriculture andAgri-Food Canada, Lethbridge, personal communica-tion). Agronomic trials investigating nutrient manage-ment and post-harvest renovation of intermediatewheatgrass began in Manitoba in 2013.

Various approaches have been presented for manage-ment of perennial grain crops, ranging from a permanentperennial polyculture of grasses, legumes, and compo-sites, mimicking a native prairie ecosystem (Piper 1998),to simpler systems in which perennial grains are includedas a phase in rotation with annual crops or in companionor relay cropping systems (Bell et al. 2010).

Perennial Polycultures. The benefits of polyculture ob-served in annual crops are also attainable in perennialcrops. Perennial forages are commonly grown in


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polyculture to provide a balanced nutritional profile andcreate yield stability under varying weather conditions.InUS studies comparing productivity of perennial prairiemixtures to monocultures of these plants, overyieldingby mixtures was greatest and most consistent in morediverse mixtures (four or more species) and increasedover the years of the study (Picasso et al. 2011; Bonin andTracy 2012). Similarly, mixtures of grasses and legumesgrown at several northern Europe sites outperformedmonocultures of these species in terms of productivityand resistance to weed competition (Sturludottir et al.2013). Overyielding in these studies was attributed to Nfixation by legumes, niche complementarity, and resourceuse efficiency in mixtures. Sanderson et al. (2007) alsosuggest that diversity in perennial forage stands providesyield stability where stresses such as drought occur andwhere there is variability in soils, landscape, and climate.As such, perennial polyculture adds a degree of resilienceto agricultural systems.

Woody Plants in Cropping Systems (Agroforestry)Agroforestry systems deliberately integrate woody plants(trees, shrubs) into agricultural production systems(Lassoie and Buck 2000). Established approaches toincorporating permanent woody vegetation into graincropping systems include field shelterbelts, multi-functional buffer strips, and alley cropping (tree-basedintercropping) systems. Agroforestry systems vary widelyin their purpose for establishment and in the physicalarrangement of crop and tree areas, but all have thepotential to contribute to the environmental sustainabil-ity and resilience of prairie cropping systems and, in somecases, provide harvestable products that enhance systemprofitability.

Adding woody plants to cropping systems throughagroforestry adds biological and functional diversity tothe system, both through planned and associated bio-diversity (Altieri and Nicholls 2008). Ecosystem servicesderived from agroforestry practices typically includepollination services from wild pollinators; suppressionof crop pests and diseases; nutrient cycling; C sequestra-tion; water purification, cycling and retention (includingsalinity management); soil conservation; and regulationof soil organic matter (Altieri and Nicholls 2008; Lin2011).

Shelterbelts and Ecobuffers. Shelterbelts or windbreakswere established widely across the Canadian prairies asa result of the Prairie Shelterbelt Program administeredby Agriculture and Agri-Food Canada since 1901. Theprimary purpose of these tree plantings was for soilconservation and snow capture, both of which are rela-ted to reducing wind speed. Shelterbelts with optimalporosity (30%) can reduce wind speed by as much as71%, and a 20% reduction in wind speed may occurover an area 25 times the height of the shelterbelt(Heisler and Dewalle 1988; Loeffler et al. 1992).

Significant reductions in soil loss from fields shelteredby trees have been observed in the Canadian prairies,along with modest increases in crop yield under certainweather conditions (de Jong and Kowalchuk 1995).While protection of soil from erosion offers a directbenefit to the producer, maintenance of soil health alsoproduces a large public, or external, benefit. The publicbenefit derived from reduced soil erosion as a result of thedistribution of tree seedlings across the Canadian prairiesover a 20-yr period has been estimated at $15�97 million(Kulshreshtha and Kort 2009). Soil moisture may alsobe increased in the vicinity of shelterbelts due to snowcapture and reduction of moisture loss from snowthrough sublimation (Kort et al. 2012). Shelterbeltsthat are well designed, with consideration of featuressuch as spacing and porosity, can optimize snow captureand distribution across the field (Canada�Alberta En-vironmentally Sustainable Agriculture 1994; Scholten1988; Kort et al. 2012). Reduction of wind speed duringsummer months may also reduce evaporative lossesand microclimate effects (increased temperature andhumidity) may increase crop water use efficiency (Davisand Norman 1988).

Shelterbelts have been associated with other benefits,such as increased soil organic C, reduced soil bulk den-sity, improved air and water quality, enhanced biodi-versity (along with associated recreational activities suchas birdwatching), reduced pesticide drift, and improvedaesthetics (de Jong and Kowalchuck 1995; Kulshreshthaand Kort 2009).

Multifunctional shelterbelts (termed ‘‘ecobuffers’’) thatdirectly enhance ecological services such as wildlifehabitat, pollination, nutrient cycling, pest suppression,C sequestration, and/or production of food, fuel, ortimber are currently being developed and investigated inwestern Canada (Schroeder et al. 2011).

Alley Cropping or Tree-based Intercropping. Alley crop-ping systems (also called tree-based intercropping sys-tems) include trees planted in widely spaced rows withagricultural crops grown in the alleys between the rows.The trees may be established for varying purposes,including fruit or nut production, timber production,or bio-energy production. Alley-cropping research inCanada has typically focused on bio-energy and timberspecies of trees, mainly hybrid poplar (Populus spp.);however, potential exists to include other types of trees,such as saskatoon berries (Amelanchier alnifolia Nutt.),sea buckthorn (Hippophae rhamnoides L.), and hardysour cherries (Prunus cerasus L.) in agroforestry systemson the prairies.

The environmental and ecological services of trees inalley-cropping systems are well documented and havebeen the focus of several studies in eastern Canada.Benefits include increased soil organic C and greater Csequestration (Thevathasan and Gordon 2004; Peichlet al. 2006; Oelbermann and Voroney 2011); reduced


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leaching of water contaminants including nitrate and E.coli (Thevathasan and Gordon 2004; Dougherty et al.2009; Bergeron et al. 2011); reduced N2O emissions(Beaudette et al. 2010); enhancement, diversification andstabilization of arbuscular mycorrhizal fungi popula-tions (Chifflot et al. 2009; Lacombe et al. 2009; Bainardet al. 2012); and augmentation of earthworm, bird andinsect populations (Thevathasan and Gordon 2004).Some of these effects have been observed in relativelyyoung agroforestry systems, only 5 to 8 yr old. Else-where in North America, researchers have observedother beneficial effects including retrieval of nutrientsfrom deep in the soil profile (Zamora et al. 2009), a shiftin arthropod communities toward parasitic and preda-tory insects rather than herbivorous arthropods (Stampset al. 2002), and increased mortality of alfalfa weevil, animportant pest of alfalfa (Stamps et al. 2009).

Alley-cropping systems can increase total productivity.A European study found that land equivalency ratios forthese systems were consistently greater than 1; however,high productivity levels depended on high soil moistureavailability and system designs that optimized comple-mentary resource use (Graves et al. 2007). In Canada,crop yields in alley-cropping systems were lower forC4 crops such as corn (Zea mays L.), similar for cool-season crops such as wheat and canola (Brassica napusL.), and variable for soybean [Glycine max (L.) Merrill],a warm-season C3 plant (Thevathasan and Gordon 2004;Reynolds et al. 2007; Dougherty et al. 2009; Rivest et al.2009; Beaudette et al. 2010). Yield reductions in thesesystems have been attributed to competition for light(Thevathasan and Gordon 2004; Reynolds et al. 2007;Rivest et al. 2009). Conversely, workers in the USMidwest have found competition for water to be themain factor in crop yield reduction (Jose et al. 2000). InEurope, crop yield in agroforestry systems was observedto decline over time, due to increased competition fromtrees as they mature (Graves et al. 2007). These studieshighlight the importance of developing tree-based inter-cropping systems that are locally adapted, allow compo-nent crops to interact in a complementary rather thancompetitive manner, and plan for stand succession.

Economic analysis of agroforestry systems is complexand US studies often compare agroforestry systemsto sole forestry operations (e.g., Benjamin et al. 2000;Stamps et al. 2009). Canadian tree-based intercroppingsystems have been found to be less profitable thanannual cropping systems, due to reduced area for annualcrops and low revenue from trees, especially when treeswere slow-growing timber species (Toor et al. 2012).Conversely, a European study found that many agro-forestry systems were economically attractive, especiallyif high-value tree species were chosen (Graves et al.2007).

Reducing TillageIn North America, particularly in dry regions, conserva-tion tillage and no-tillage are widely practiced for soil

moisture conservation, soil protection from wind andwater erosion, and to reduce fuel use in farm operations(Derpsch et al. 2010). Positive effects of no-till on soilhealth parameters have been widely documented andinclude major reductions in soil erosion and fuel con-sumption, reduced CO2 emissions, and enhanced waterquality, biological activity, soil fertility and productionstability (Pretty 2008; Derpsch et al. 2010; Lafond et al.2011 and references therein). Studies in the NGP havealso reported better soil aggregation, enhanced soilorganic C, and increased potentially mineralizable Nin no-till soils (McConkey et al. 2003; Liebig et al. 2004;Pikul et al. 2009; Malhi et al. 2009; Lafond et al. 2011).Microbial biomass, especially of mycorrhizal fungi, isoften, but not always, greater in no-till soils (Liebig et al.2004; Helgason et al. 2010; Monreal et al. 2011); soilorganism community structure may also be different inno-till than tilled soils (Helgason et al. 2010).

Yields of crops under no-till vary, depending on cropspecies and weather conditions (e.g., Malhi and Lemke2007). No-till often increases crop yields and water useefficiency under dry conditions, but can result in reducedyield under wet conditions (Azooz and Arshad 1998;Arshad et al. 2002). Reduced Nmineralization under no-till may also reduce yields where N is limiting (Campbellet al. 2011). Lafond et al. (2011) observed that N uptakeand yields in long-term (31 yr) no-till exceeded those inshort-term (9 yr) no-till, suggesting that even after 9 yr,and possibly even after 31 yr, no-till soils may still be in asoil-building phase. No-till systems may offer an addi-tional contribution to sustainable cropping systems byfacilitating the cycling of perennial forages in rotation(Allen and Entz 1994).

Conservation agriculture is defined by a broader set ofprinciples that include diversity of crop rotations alongwith minimal soil disturbance and retention of cropresidue on the soil surface (Scopel et al. 2013). Conserva-tion agriculture is being implemented widely in tropicalcountries, particularly those using non-mechanized farm-ing practices, with major improvements in crop yieldsand soil health (Derpsch et al. 2010). Strengthening cropdiversity through improved rotations and cover cropsin Canadian prairie no-till systems could have majorbenefits for their productivity, sustainability, and resi-lience. The Brazilian model of conservation agriculture,in which cover crops and grazing livestock are central tothe system (e.g., Carvalho et al. 2010; Santos et al. 2011),could inform our Canadian prairie systems. For instance,inclusion of N-rich legume cover crops and grazinglivestock could enhance N mineralization and provideweed management options that would allow our no-tillsystems to reduce their current reliance on herbicides.

Endogenous Input SystemsNatural ecosystems function on the principle of microbe-mediated nutrient recycling within the system, withlimited external inputs. In contrast, most moderncropping systems have become heavily dependent on


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synthetic fertilizer application for delivery of nutrients tocrops (Drinkwater and Snapp 2007). The high energetic(Hoeppner et al. 2006; Bavec et al. 2012) and financialcost of fertilizer, nutrient losses to the environment,and the effects of synthetic fertilizer use on soil organicmatter and soil microbial communities (Janzen et al.2003; Drinkwater and Snapp 2007; Phelan 2009) have ledmany to consider ways of reducing fertilizer use andinstead provide crops with at least a portion of requirednutrients from within the system (endogenous inputs).Phelan (2009) asserts that ‘‘[u]nderstanding the opera-tion of detrital food webs and designing agriculturalnutrient management that is more consistent with thenutrient cycles of natural systems is the single most im-portant step that can be taken to increase the economicsustainability, environmental compatibility and biologi-cal resilience of agricultural systems.’’ Because agricul-tural systems necessarily export some nutrients, entirelyclosed-loop systems will be impossible to achieve untilsafe and efficient means of recycling human nutrients canbe implemented. However, considerable potential existsto enhance the cycling of nutrients within croppingsystems so that external inputs can be minimized. Daviset al. (2012) suggest that productivity and environmentalsustainability can be optimized in a system that is drivenby endogenous inputs and ‘‘tuned’’ using small amountsof external inputs.

Endogenous inputs have additional impact on thehealth of farming systems due to their form, in additionto their source. C-based nutrient sources, such as animalmanure and green manure crops, are known to increaseabundance and diversity of soil fauna and to enhanceplant health and resistance to pests by preventing ex-cesses of free amino acids in plants (Phelan 2009). Inaddition, use of diverse nutrient inputs, including orga-nic residues and BNF, builds more stable reservoirs ofnutrients in soil, reducing losses to the environment(Drinkwater and Snapp 2007).

Animal Manure and CompostUse of animal manure as a nutrient source for crops hasdiminished with the separation of crop and livestockproduction systems and the availability of easy-to-usesynthetic fertilizers (Davis et al. 2012). As a result,animal manure is often treated as a waste product ratherthan as a source of fertility and organic matter for crop-ping systems. However, recognition of the beneficialeffects of livestock manure is growing, along with aware-ness of how to mitigate potential water and air qualityissues.

Many studies have observed excellent crop responseto manure application, with yields often equal to or nearthe yield obtained with synthetic fertilizers (Blackshaw2005; Miller et al. 2009; Olson et al. 2010; Buckley et al.2011). Much of the benefit to crops is through nutrientsupply, but non-nutrient benefits are also important. Ina moisture-limited growing season in Utah, application

of composted manure increased the moisture retentioncapability of soil, improving yield (Stukenholtz 2002). InSaskatchewan, crops grown in cattle or hog manure-amended soils had better vigour and were less affectedby common root rot (de Freitas et al. 2003).

Manure application to farmland also enhances soil C,microbial biomass, microbial activity, and populationsof nematodes and natural enemies of crop pests (deFreitas et al. 2003; Snapp et al. 2010; Garratt et al. 2011;Hu and Qi 2011; Moulin et al. 2011). Carry-over effectson crop yield and other benefits to subsequent years arealso commonly observed (e.g., Endelman et al. 2010).Reeve et al. (2012) observed positive effects on cropyield, soil organic C, and microbial biomass 16 yr aftercompost application in dryland wheat.

Manure application at high rates and/or frequency canresult in nutrient accumulation in soils, contaminationof surface and ground water, and increased GHG emis-sions (Stumborg and Schoenau 2008; Ashjaei et al. 2010;Miller et al. 2010, 2011, 2012). Appropriate managementpractices such as those described by Shoenau and Davis(2007) and others can effectively mitigate the potentialfor nutrient loss and environmental contamination.Nutrient build-up can be prevented by applying manureto meet the P, rather than N, requirements of the crop orhaying manure-amended grasslands rather than grazing(Olson et al. 2010; Wilson et al. 2011). Including a high-Csubstrate, such as wood chips, in manure can also reduceN loading to the system (Miller et al. 2011). Incorporat-ing manure into soil reduces volatilization of N (Schoenauand Davis 2006) and nutrient losses to surface water(Jokela et al. 2012). Even though N leaching frommanure and compost can occur, it is often less thanleaching from synthetic fertilizers, even when total Ninputs are equal to or higher than synthetic N inputs(Pimentel et al. 2005; Snapp et al. 2010).

While the mixed-farm model provides the simplestframework for recycling manure nutrients back to crops,improved manure processing and application practicesallow for novel approaches to using manure on cropland.Transporting liquid manure long distances is energyintensive (Wiens et al. 2008) and has prompted researchon methods to separate solid and liquid componentsof liquid manures (e.g., Fangueiro et al. 2012; Xia et al.2012) and on the agronomic effects of the resultingcomponents (e.g., Bittman et al. 2011). Implements forimproved application of solid manure are also beingdeveloped (e.g., Lague et al. 2006). Composting manuremay enhance its agronomic and soil health benefits(Lynch et al. 2005).

Green Manures and Biological N FixationBiological nitrogen fixation by legumes currently pro-vides only about 18% of N inputs in Canadian agricul-ture [calculated from Janzen et al. (2003)]. Thus, there isconsiderable potential to explore agricultural systemsthat make better use of legumes for BNF.


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Perennial forages and annual green manure cropsoffer the greatest potential for soil enrichment with N,while grain legumes and short-duration cover crops cancontribute smaller amounts of N to the system. Alongwith N fixation, legume green manures in rotation addorganic matter, cycle other nutrients, suppress weeds,disrupt pest cycles, and enhance soil physical, chemical,and biological properties (Fageria 2007).

The yield of crops following legume green manurecrops depends largely on biomass production (and asso-ciated N fixation and subsequent mineralization) of thegreen manure. In moisture-limited regions, water use bythe green manure crop may also be a major factor. Anannual legume green manure such as black lentil (cv.Indianhead), chickling vetch (Lathyrus sativus L.), fieldpea, or hairy vetch can typically contribute 50�150kg N ha�1 in the Canadian prairies, depending on greenmanure species and biomass production (Bullied et al.2002; Thiessen Martens and Entz 2011; Vaisman et al.2011). Early termination of green manures where moist-ure is limiting effectively optimizes water availability tothe following crop and N fixation by the green manure(Zentner et al. 2004; Allen et al. 2011). In semiaridenvironments, where green manure biomass productionis relatively small, it may take several crop rotation cyclesfor a legume green manure to accumulate sufficient N toproduce yields equal to fertilized treatments (Zentneret al. 2004; Allen et al. 2011). Green manures alsoenhance many soil biological parameters, includingpopulations of soil bacteria and fungi, soil microbialbiomass N and C, and microbial activity (Biederbecket al. 2005).

The economics of green manures in rotation com-pared with synthetic fertilizer use depend largely onthe price of fertilizer, green manure establishment costs,and the yield benefit realized due to the green manure.In a study where green manures were produced in placeof summerfallow, reductions in fertilizer requirementsmore than offset the cost of green manure establishmentafter several crop rotation cycles with good soil watermanagement practices (Zentner et al. 2004). However, incontinuous cropping systems, green manure productionrequires farmers to forfeit a year of cash crop produc-tion, negatively affecting the economics of the system.Obtaining some direct economic value from a green man-ure crop through grazing (Thiessen Martens and Entz2011) or seed harvest (Chen et al. 2012) can improve netreturns, although seed harvest reduces subsequent cropyields (Chen et al. 2012).

Soil Biological FertilitySoil biological fertility links a healthy soil with the abilityto deliver nutrients to plants and is defined as ‘‘thecapacity of organisms living in soil (microorganisms,fauna and roots) to contribute to the nutritional require-ments of plants and foraging animals for productivity,reproduction and quality . . . while maintaining biological

processes that contribute positively to the physical andchemical state of the soil’’ (Abbott and Murphy 2007).Soil biological fertility is still poorly understood but isseen as an important contributor to the sustainability ofagricultural systems due in part to more balanced plantnutrition and lower risks of nutrient loss (Drinkwater andSnapp 2007; Phelan 2009).

Organic matter additions (crop residue, farmyardmanure, and green manure), legume-containing pastures,diverse crop rotations and crop mixtures, minimum orno-till systems, livestock grazing, and application ofcertain inoculants are known to enhance soil biologicalfertility, with positive effects on chemical and physicalattributes of soil as well; tillage and application offertilizers and pesticides, on the other hand, generallyinhibit soil biological activity (Abbott and Murphy2007; Clapperton et al. 2007; Nelson and Spaner 2010;Druille et al. 2013). Crop diversity appears to be one ofthe most important contributors to soil biological fer-tility (Drinkwater and Snapp 2007). Nelson and Spaner(2010) conclude that both no-till farming systems thatlimit inputs and organic farming systems that limittillage could create conditions that favour soil biologicalfertility, if crop diversity is high (i.e., including covercrops and intercrops).

Developing management practices that promote spe-cific plant nutrition goals is difficult due to our limitedknowledge of soil microorganisms and their function,as well as the dynamic and site-specific nature of soilbiological fertility (Abbott and Murphy 2007). Investi-gations into the role of soil biological activity in cropuptake of P, for example, have produced varying results.There is evidence that soil�plant�microbe interactionscan enhance P uptake by plants through more thoroughsoil exploration (i.e., through hyphal networks of mycor-rhizal fungi) and/or enhanced P solubility due to rootexudations and associated effects on enzyme activityor soil pH (Marschner and Rengel 2007; Conyersand Moody 2009). This effect has been observed ina long-term organic-conventional comparison study inManitoba, where flax (Linum usitatissimum L.) grain Pconcentration was higher in organic production systemsthat had lower plant-available P and higher levels ofmycorrhizal colonization than in conventional produc-tion systems that had higher soil P and lower levels ofmycorrhizal colonization (Entz et al. 2004; Welsh 2007;Welsh et al. 2009). Others have observed net negativeimpacts of mycorrhizal colonization on organic wheatyield due to excessive C demand by the mycorrhizalfungi on the crop (Dai et al. 2014). Based on a reviewof Australian literature, Ryan and Kirkegaard (2012)indicate that crop production practices to enhancemycorrhizal colonization are not generally effective inAustralia, but may be worth exploring in regions suchas Canada, where more mycorrhizal crops are grown.Drinkwater and Snapp (2007) suggest that loss ofdiversity and function in microbial communities due tocurrent agricultural practices may have caused a shift


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in some plant�microbe interactions from mutualistic toparasitic relationships.

Organic SystemsOrganic farming is a system that relies heavily on endo-genous inputs. While a range of practices is permittedunder the Canadian organic production standards, thereis a clear emphasis on environmental sustainability andecological integrity [Canadian General Standards Board(CGSB) 2006].

In the Canadian prairies, organic farmers typicallymanage soil fertility through crop rotation, green manu-res, forages in rotation, and manure or compost applica-tions, while weeds are generally managed throughcultural means such as high seeding rates or mechanicalmeans such as tillage (Nelson et al. 2010). Averagewheat, oat, barley, and flax yields on 14 organic farmsin the eastern prairies were 73�78% of the long-termconventional average yields (Entz et al. 2001), in agree-ment with a recent meta-analysis (Seufert et al. 2012).According to surveys of organic farmers in the Cana-dian prairies, crop rotations, soil fertility and health,and weed management are the major production chal-lenges (Frick et al. 2008; Organic Agriculture Centre ofCanada 2008a, b).

Despite lower yields, organic production systems areassociated with a number of benefits. Organic systemspromote biodiversity in a wide range of faunal groupsincluding arthropods, soil biota, and farmland birds,with some direct enhancement of ecosystem servicessuch as pest predation and pollination (Morandin andWinston 2005; Crowder et al. 2010; Garratt et al. 2011;Power et al. 2012; Winqvist et al. 2012). Organic systemshave lower ecological footprints (Bavec et al. 2012),have increased energy efficiency (Hoeppner et al. 2006;Zentner et al. 2011b), and enhance a number of soil andnutrient parameters such as soil C and nutrient retention(Pimentel et al. 2005). Increased soil organic matter inorganic systems can also contribute to improved cropyield in years of moisture deficiency (Stukenholtz 2002;Lotter et al. 2003). Organic inputs in the form of lives-tock manure or compost support both the productivityand sustainability of organic systems. Manure/compostadditions enhance yields of organic crops (Pimentelet al. 2005; Bavec et al. 2012) and have been observed tobuild up soil C (54% increase) and reduce N leaching(50% reduction) compared with systems using syntheticfertilizers (Snapp et al. 2010).

Economic analysis of organic vs. conventional farm-ing systems has shown that organic systems are ofteneconomically competitive with conventional systems dueto their lower input costs, premium prices for products,direct marketing opportunities, and resilience to weatherextremes (MacRae et al. 2007). In long-term experi-ments in Saskatchewan, Minnesota, and Iowa, organicsystems had net returns greater than or equal toconventional systems, but these levels of return were

dependent on organic premiums for at least some crops(Delate et al. 2003; Delbridge et al. 2011; Zentner et al.2011a). Income variability may be lower in organicsystems (Pimentel et al. 2005; Zentner et al. 2011a).

The value of organic farming to long-term sustain-ability of agricultural systems is often hotly debated; thisdiscussion tends to focus on the (lack of) productivityof organic systems versus the environmental damageand reliance on external inputs of conventional systems.The range of farming practices employed in bothorganic and conventional farming systems makes cate-gorical comparison extremely difficult but is instructivein determining which aspects of each farming system arebeneficial or detrimental. Poorly designed organic farm-ing systems with low productivity tend to deplete soilorganic C (Bell et al. 2012; Leifeld 2012) and are thusboth unprofitable and environmentally unsustainable.In contrast, well-designed organic farming systems thateffectively harness ecological processes are both pro-ductive and environmentally sustainable (Halberg 2012).Organic systems also have potential for mitigation ofclimate change through reductions in N2O emissions,elimination of synthetic fertilizers, and C sequestration,and for adaptation to climate change through farmdiversification, building of soil organic matter, and inde-pendence from external inputs (Scialabba and Muller-Lindenlauf 2010).

Nutrient exports in excess of nutrient inputs can resultin eventual mining of soil nutrients in organic systems(Welsh et al. 2009). While nutrient cycling in organicsystems may be enhanced through the use of manure,crop�livestock integration, and soil biological fertility,it is necessary to close nutrient cycles in agriculturalsystems more completely to create systems that aresustainable in the long-term. This will require recyclingof nutrients contained in human waste, a practice notcurrently permitted in certified organic systems (CGSB2006).

Integrated Crop�Livestock SystemsThe goal of integrating crops and livestock is ‘‘integrationof function rather than mere diversification’’ (Schiereet al. 2002). These functions involve nutrient cycling,consumption and ‘‘processing’’ of crop residues, and pestmanagement (for both crops and livestock), among others.The benefits of crop�livestock integration also includeincreased income and income stability (Franzluebbersand Stuedemann 2007; Russelle et al. 2007) as well as thepotential to reduce GHG emissions from both crop andlivestock systems (Asgedom and Kebreab 2011). Crop�livestock integration plays a supporting role in otherbeneficial cropping practices since some techniques, suchas growing green manures, cover crops, annual andperennial forages, and agroforestry systems becomemore financially attractive when livestock products canbe gained from the system (Gardner and Faulkner 1991;Clason and Sharrow 2000; Thiessen Martens and Entz2011; Chen et al. 2012).


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While crop�livestock integration is common in per-ennial forage-based systems, many other possibilitiesexist. Annual cropping systems offer many opportunitiesfor integration of ruminants, and pigs and poultry canprovide unique services such as rooting (tillage) andselective weed grazing or insect predation (Entz andThiessenMartens 2009 and references therein). Ecologicalfunctions may be enhanced even further when livestockare integrated into more complex systems such as agro-forestry and even aquaculture (Mcadam et al. 2007; Entzand Thiessen Martens 2009; Haile et al. 2010). Optimiza-tion of crop�livestock systems in the prairie regionrequires further exploration of the relationships amongsoil, crops, uncultivated areas, and livestock, includingthe role of nutrient transformation and redistribution bylivestock, the effects of specific grazing strategies on soilhealth, and the role of livestock in management of weedsand natural vegetation.

Integration can occur either on a single mixed farmor in a cluster of various types of specialized farms.The most common approach to area-wide integrationinvolves hauling of manure or compost from livestockoperations onto surrounding farmland. Another optionis to move the livestock onto farmland in custom graz-ing operations or other arrangements between crop andlivestock farmers. Proximity of farms and trust betweenfarmers are keys to the success of such systems (Entzand Thiessen Martens 2009).

NutrientsThe role of livestock in cycling of nutrients, especially Nand P, is perhaps the most important reason for crop�livestock integration (Entz and Thiessen Martens 2009).Nutrients in plant material consumed by livestock,especially ruminants, are converted quickly into moreplant-available forms, thus accelerating nutrient cycles.Interestingly, the microbial processes responsible for thisconversion in the rumen are also more efficient than soilmicrobial processes (Russelle 1992). With accelerationof nutrient cycles, however, comes increased risk of loss.Thus, crop�livestock systems require careful planning andcontinual assessment to optimize the use of nutrients.

Integration of crops and livestock can result in semi-closed nutrient cycles. Organic and biodynamic dairyfarms in Ontario and Australia had P balances near zeroon average; however, nutrient exports in agriculturalproducts can result in a negative P balance even onmixed farms, especially when little or no feed is pur-chased (Lynch 2006; Cornish 2007). Purchasing feedfrom off the farm allows for P inputs without usingsynthetic fertilizers or rock P (Gordon et al. 2002).Knowledge of nutrient concentrations in feed andmanure is important for effective management.

Grazing in Annual Cropping Systems

Swath, Bale, and Crop Residue Grazing. Alternative winterfeeding systems, in which cattle are fed baled or swathed

forages on pasture or cropland or allowed to graze cropresidues such as corn stover can reduce overall costsby reducing forage harvest and manure hauling costs(Volesky et al. 2002; McCartney et al. 2004; Karn et al.2005), if costs associated with watering systems, foragewastage, and checking cattle are not excessive (Nayigihuguet al. 2007).

These feeding systems also have potential to enhancenutrient return to farmland and the performance ofsubsequent crops. In two Saskatchewan studies, soil Nand P concentrations, nutrient recovery, and subsequentcrop productivity were increased in at least some fieldlocations after bale or swath grazing on annual crop-land or grass pasture (Jungnitsch et al. 2011; Kelln et al.2012). However, bale grazing systems can result innutrient excesses and risk of environmental contamina-tion at some points (Kelln et al. 2012) as well as elevatednutrient levels in spring run-off (Smith et al. 2011).

Both swath and bale grazing systems can be imple-mented using annual or perennial forages, on either annualcropland or perennial hay or pasture. Bale grazing offersthe potential for nutrient transfer within a system byplacing bales in strategic locations such as areas withlower soil fertility.

Green Manure/Cover Crop Grazing. Integrating grazinglivestock into green manure or cover cropping systemshas potential to improve the economics and thus theadoption potential of BNF by legumes in rotation(Gardner and Faulkner 1991; Sulc and Tracy 2007;Thiessen Martens and Entz 2011).

Crops used as annual green manures in the Canadianprairies typically have high forage quality but vari-able palatability to livestock and tolerance to grazing(Marten 1978; Gardner and Faulkner 1991; Miller andHoveland 1995; Fraser et al. 2004). Certain negativeeffects on animal health associated with grazing legumegreen manures, cereals, or brassicas have been obser-ved (Gardner and Faulkner 1991; Johnson et al. 1992;Panciera et al. 1992; Hannaway and Larson 2004; Raoet al. 2005; McCartney et al. 2008, 2009; McCartneyand Fraser 2010); however, animal health risks posedby grazing can generally be minimized through cropcultivar selection and grazing management.

While research into these systems is limited, resultsindicate that crop yields following grazed green manuresare equal to those following green manures that werenot grazed (Franzluebbers and Stuedemann 2007; Ciceket al. 2014b, c). Grazing can, however, increase Navailability in the soil in the fall, creating N leachingpotential; fall catch crops may be useful for preventingN leaching following grazed green manures (Cicek et al.2015).

The effects of grazing cover crops on soil health are amajor motivator for those producers who are using thissystem. Fraase et al. (2010) reported that soil bulk densitydecreased from 2009 to 2010 where turnip (Brassica


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campestris var. rapa Linn.) and ‘‘cocktail’’ cover cropswere produced and grazed. In other regions, researchershave found that grazing increased soil microbial biomass(Franzluebbers and Stuedemann 2008a) but had no effecton bulk density or soil aggregate stability (Franzluebbersand Stuedemann 2008b).

FarmscapingFarmscaping refers to the ‘‘modification of agriculturalsettings, including management of cover crops, fieldmargins, hedgerows, windbreaks, and specific vegetationgrowing along roadsides, catchments, watercourses, andadjoining wildlands’’ (Bugg et al. 1998). In farmscaping,the role of landscape pattern and diversity in providingbenefits to agricultural systems is central. Commonfarmscaping techniques include establishment of areasof perennial vegetation and protection and managementof riparian zones and small-scale wetlands (Long andPease 2005; Smukler et al. 2010). While farmscaping canbe implemented in any farming system, Kirschenmann(undated) argues that mid-sized farms are better thanlarge farms at preserving wildlife habitat, and Garrattet al. (2011) and Halberg (2012) suggest that organicfarms tend to have a higher degree of landscape diversitydue to smaller field size and an inclination to preservenatural areas. Better understanding of the role of land-scape-scale processes and landscape features is necessaryto develop farmscaping practices that optimize therelationships between cropland and uncultivated areas.

The benefits of farmscaping to agricultural systems arelargely due to enhanced associated biodiversity, specifi-cally of beneficial organisms including wild pollinatorsand natural enemies of crop pests (e.g., Garratt et al.2011; Morandin and Kremen 2013), as a result ofplanned biodiversity (Altieri and Nicholls 2008; Liebmanand Schulte 2015). Additional benefits of these perma-nent landscape features can include other ecosystemprocesses such as nutrient cycling, soil C sequestration,capture of sediment and nutrients in run-off, waterfiltration, and enhancement of the local and regionalwater cycles (van de Kamp and Hayashi 1998; Pretty2008; Smukler et al. 2010; Gleason et al. 2011; Liebmanand Schulte 2015); provisioning services such as fruit orforage production from these landscape features them-selves (Zink 2010); and increased productivity fromsurrounding cropland (Morandin and Winston 2006;Liebman and Schulte 2015). Disproportionately largeecological benefits may be realized by converting smallareas of cropland to herbaceous perennial vegetation,creating unique habitats throughout the farm, or using afew key species of woody plants in the farm landscape(Smukler et al. 2010; Liebman and Schulte 2015).

Opportunities for farmscaping in Canadian prairiefarming systems include strategic development andmanagement of riparian buffer zones, field shelterbeltsand ecobuffers, and agroforestry systems. An opportu-nity exists in irrigated crop production utilizing centrepivots where unirrigated field corners could be planted

to perennial herbaceous or woody vegetation (Zink2010). In addition, natural and constructed wetlands,both permanent and ephemeral, provide crucial habitatfor waterfowl (Shutler et al. 2000) and capture solublenutrients lost from elsewhere in the system (Drinkwaterand Snapp 2007).

In many cases, the benefits of farmscaping aredifficult to quantify in economic terms. However, anexample from northern Alberta indicates that increasedyield of canola in close proximity to uncultivated areaswould more than offset the cost of taking this land outof cultivation, due to better pollination and seed set(Morandin and Winston 2006).

ASSESSMENT OF FARMING PRACTICESFOR THEIR ROLE IN THE SUSTAINABLEDEVELOPMENT OF CANADIAN PRAIRIE

CROPPING SYSTEMSThe farming practices reviewed in this paper range fromrelatively simple modifications to the types of systemicchanges suggested by Gliessman (2010). While somepractices are well understood and established in practice(e.g., crop rotation, no-till), others are in their infancyand require more research and development (e.g., soilbiological fertility, farmscaping). In many cases, we donot have complete knowledge of the impacts of particularpractices on specific criteria related to profitability,sustainability, and resilience, especially for the Canadianprairie region, nor do we fully understand the interac-tions among practices and components or the relativeimportance of various criteria. Thus, it is difficult tocompare the net impact of these practices. However,it is possible, based on the literature already discussed,to identify some general characteristics of agriculturalsystems that tend to be profitable, sustainable, andresilient and to evaluate the practices described in thisreview based on how closely they adhere to the principlesthat support these characteristics.

Agricultural systems that most closely mimic naturalsystems appear to be the most resilient and environmen-tally sustainable due to their biological and enterprisediversity; integration, multifunctionality, and redundancyamong components; effective nutrient cycling throughpromotion of soil biological activity and minimal useof external inputs; leveraging of natural ecosystemprocesses; and minimal soil disturbance (Lin 2011;Malezieux 2012). Diversity lends stability (both ecolo-gical and economic) and effective integration of systemcomponents builds integrity and allows for realizationof synergies among processes (Elton 1958; Altieri 1999;Gliessman 2010; Malezieux 2012). Profitability of suchsystems will depend in part on the choice of agriculturalspecies and optimization of synergies among components.It is important to note that these ecologically basedwhole farm systems have not yet received much researchattention and, therefore, have the most uncertainty asso-ciated with them. Given their potential benefits, they


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deserve significantly more research and developmentattention.

Based on these characteristics, farmscaping, crop�livestock integration, agroforestry, perennial forages,and perennial grains, complemented with endogenousinput systems and minimal soil disturbance, have thepotential to make large contributions to sustainabilityand resilience. When such systems are designed to com-ply with organic production standards, market pre-miums further enhance their profitability. Perennialforages in particular have a large and well-documentedpositive impact on environmental sustainability andresilience and are also technically feasible. While per-ennial grain systems appear promising, implementationof such systems is impossible until varieties becomecommercially available. Applied research on integratedcrop�livestock systems, alley cropping, and farmscaping(including shelterbelts and ecobuffers) is needed tooptimize and support implementation of these practicesin the prairie region. Local farmer knowledge of crop�livestock systems and farmscaping practices may bemore developed than local research in these areas, asecologically minded farmers make observations andexperiment with practices on their own farms.

Profitability, sustainability, and resilience can beenhanced to some degree by adding diversity to annualcropping systems without a major change in the system.Practices that can be implemented relatively easily withinannual cropping systems include crop selection androtation, cover crops, reducing tillage, animal and greenmanures, soil biological fertility, annual polyculture, andcrop varieties and genetics. Even these practices havechallenges associated with their implementation. Forinstance, optimal use of crop rotation may be limitedby poor markets for all but a few crops, which causesfarmers to shorten their rotations, and the sustainabilityof no-till farming is limited by its reliance on herbicides.Finding a temporal niche for cover crops in the shortgrowing season of the prairies remains a challenge, butnovel ways of including and using cover crops, perhapsin integrated crop�livestock systems, would increase theadoption potential and realized benefits. A shift to theuse of endogenous inputs in cropping systems requiresgreater knowledge of how to manage these systemseffectively. While some of these practices individuallymay have a relatively low impact on sustainability, profi-tability, and resilience, they remain useful during thetransition to redesigned integrated systems and are im-portant components of fully redesigned systems (Gliessman2010).

The challenges associated with implementing indivi-dual diversification practices highlight the importanceof taking a holistic, integrated approach to designingagricultural systems. This ecological approach to agri-culture involves using nature as a model to guide thedesign and management of farming systems, with parti-cular attention to the structures and processes occurringin natural systems and adaptation to local conditions

(Malezieux 2012). Sustainable agricultural systems de-pend on ecological processes that promote qualities suchas soil fertility, pest resistance, pollination, and produc-tivity, but also on social processes that generate knowl-edge and incentives for producing a variety of foodand fibre using locally affordable methods. Thus, a trulyecological approach to agriculture is one that linksecology, culture, economics, and society to sustainableagricultural production, healthy environments, and viablefood and farming communities that are able to adapt tochange and persist in the long-term (Gliessman 2010;Cabell and Oelofse 2012).

Ecological agriculture may encompass many or allof the practices already discussed in this paper and, assuch, may realize the benefits attributed to individualpractices. More importantly, an integrated approach todeveloping a whole farm system can also create synergiesamong individual practices and enhance the benefits tothe system, if diverse components are ‘‘correctly as-sembled in space and time’’ (Altieri 1999) with attentionto integration of function (Schiere et al. 2002). Research-ers in Minnesota determined that highly diversified andecologically integrated farm operations and landscapeswould provide greater economic, environmental, andsocial benefits than systems employing a set of bestmanagement practices (Boody et al. 2005). Intensifica-tion of ecological farming systems through carefulmanagement of biological processes may allow for highlevels of both food production and ecosystem services(Dore et al. 2011).

Our understanding of ecological processes in agri-culture is still poorly developed and the applicationof concepts in location-specific recommendations isoften lacking. Because agroecological systems are to bemodelled after the native ecosystems of the region, localresearch to develop these systems is needed around theworld and, specifically, in the various ecozones of theCanadian prairies.

CONCLUSIONThis review demonstrates that agricultural systemsdesigned according to ecological principles and localecologies contribute to better outcomes for the agricul-tural systems of the Canadian prairies. We have arguedthat these systems require systemic change if profitability,sustainability, and resilience are to be optimized. Just asthe key ecological pillars of diversity and integration lendstability and integrity to ecosystems, integrating diversecomponents in ecologically compatible complementaryrelationships within supportive economic and socialstructures promotes the overall health of the system,including environmental sustainability, long-term profit-ability, and resilience to shocks and stresses. Thus, systemchange requires purposeful and proactive redesign ofagricultural systems at all levels, from individual farms toregional and even global scales, with particular attentionto functional integration of diverse components.


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The challenge to align Canadian prairie agriculturalsystems with ecological principles is immense, especiallyin the current context of agricultural development whereshort-term productivity and economic efficiency areemphasized. However, the more holistic goals encom-passed in ecologically based systems are fundamental tothe long-term success of any sector or society and areworthy of serious pursuit. Past government and univer-sity scientists in the prairies have also called for systemredesign with a shift to ‘‘permanent agriculture’’ based ondiversified crop rotations and effective crop�livestockintegration (Janzen 2001). Had our agricultural policymakers, educational institutions, and businesses em-braced this advice, we would be much further aheadthan we are today. We believe that locally adaptedecological prairie farming systems are still achievablebut will require a major shift in research, education, andpolicy. A proactive move in this direction would providea solid foundation for the development of environmen-tally sustainable, profitable, and resilient agriculturalsystems in prairie Canada.

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