Cultivating biodiversity to transform African agriculture
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This document discusses how cultivating biodiversity can transform African agriculture. It argues that ecologically intensified farming systems that maximize the use of natural resources through increased biodiversity outperform conventional systems. Biodiversity at multiple scales optimizes plant functional traits, regulates pests and diseases, and amplifies biogeochemical cycles in soil. Examples show how intercropping, agroforestry, and plant diversification improve productivity while reducing inputs and externalities. Research needs to support context-specific, farmer-led innovation and the development of complex cropping systems adapted to local conditions through plant breeding and functional ecology. In situ conservation of agrobiodiversity must also be supported to ensure future resilience and adaptation.
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Cultivating biodiversity to transform African agriculture
- 1. Cultivating biodiversity to transform African agriculture Montpellier Panel side event Fara Science Week 2013 Etienne Hainzelin
- 2. Cultivating biodiversity to transform African agriculture Increasing the production with a brand new vision of performance 1.Natural and cultivated ecosystems are not separated any more 2.Biodiversity is the driving force of this ecological intensification 3.New paradigm and needs for research
- 3. Compared intensitivity of cropping systems (adapted from M. Griffon 2013) Natural resources + functionalities Inputs Products / biomass Positive externalities Negative externalities Conventionally intensified farming systems
- 4. Natural resources + functionalities Inputs Products / biomass Positive externalities Negative externalities Ecologically intensified farming systems Compared intensitivity of cropping systems (adapted from M. Griffon 2013)
- 5. 2. Agrobiodiversity is the driving force for ecological intensification To make the best use of natural resources, we need to maximize the biomass production, by intercepting throughout the year the most of solar radiation, CO2, N, … by: • Optimizing plant functional biodiversity at different scales and revisiting plant breeding to adapt plants to complex association; • Optimizing functional biodiversity at different scales regulating bio- agressors; • Amplifying biogeochemical cycles in the soil, recycling the nutrients from deep profiles and increasing microbial activities.
- 6. Increased number of cultivated species Optimizing plant functional biodiversity means complexification of cropping systems
- 7. Ex1. Complexification of cropping systems in Mato Grosso (1980-2010) Source: L. Seguy et al., (2009) La symphonie inachevée du semis direct dans Brésil central http://agroecologie.cirad.fr/librairie_virtuelle
- 8. Increasing functional biodiversity to control bio-agressors Push-pull Natural enemy conservation Resource concentration Climate change Barrier effects Allelopathy Cycle ruptureRoot action Plant biomass Plant diversification Reduced pest & disease impact Tolerance to pests & diseases Improved plant hydric & mineral nutrition Soil suppressiveness Porosity Mineralisation Below ground soil biota diversity/ activity enhancement
- 9. Ex 2. Increased plant biodiversity to control crop pests and diseases Natural enemy conservation Resource concentration Climate change Barrier effects Allelopathy Cycle rupture Plant biomass Plant diversification Reduced pest & disease impact Tolerance to pests & diseases Improved plant hydric & mineral nutrition Soil suppressiveness Porosity Mineralisation Below ground soil biota diversity/ activity enhancement Push-pull Source: The ICIPE push-pull Platform, http://www.push-pull.net/works.shtml Chemicals secreted by desmodium roots inhibit attachment of striga to maize roots and cause « suicidal germination » of striga seed in soil Allelopathic effect
- 10. Association of two rice genotypes to reduce Pyricularia incidence
- 11. Various intercropping systems of crops (flax, soybean, maize) in Gansu Province, China. Maize/soybean/flax intercropping in Gansu Province, China Wheat/maize strip intercropping in Gansu Province, China. Wheat/maize intercropping practiced by local famers in Ningxia, Northwest China. Li et al., 2013 Encyclopedia of Biodiversity 2nd Edition 382-395
- 12. Multiples examples of agroforestry From planified associated cropping …… to complex agroforests
- 13. Integration orchards / goat or poultry Integration rice/ducks, etc.
- 14. • By minimizing the loss of nutrients (leaching, erosion,…). • By recycling the nutrients from deep soil profiles (deep rooting species, second crop at the end of the rainy season,…). • By increasing microbial activities and stimulating the “rhizosphere” effects (biogenic structures). Soil Solution Permeases Enzyme secretion Soil Microorganisms Low Mol. Wt compounds Intracellular enzymes 1. Energy 2. C,N,S,P Low Mol. Wt compounds Polymers (C,N,S,P) Soil Mineral Surfaces Extracellular enzymes Soil Organic Matter Permeases Enzyme secretion Amplifying biogeochemical cycles Credit: H. Saint Macary Adapted from Quiquampoix & Burns 2007 Roots
- 15. The soil « engineers »
- 16. Unveiling the hidden agrobiodiversity in the soil The functional traits of the soil organisms (from E. Blanchard) Functional groups Micro-regulators Engineers Shredders Decomposers N captors + Roots Relationship with microorganisms and formation of biogenic structures
- 17. - The importance of local context: shift from “ready-to-use” to “custom- made” cropping systems put the producers at the center of local innovation systems, to combine technologies and traditional knowledge. - Agrobiodiversity, a key component of resilience, must remain accessible to small farmers, as a capital for future adaptation. In situ conservation of must be supported as a complement of ex situ conservation; - Need for sectoral policies in favor of agrobiodiversity and sustainable intensification (access to market, payment of environmental services, etc.); - The new roles for research: importance of basic knowledge on functional ecology; rethinking plant breeding; dealing with management of complex cropping systems and coping with multi-criteria performance; taking into consideration local knowledge and remain in strong personal interactions with agricultural realities. 3. New paradigm and needs for research
- 18. A Cirad collective book with 15 authors of different viewpoints and disciplines Agrobiodiversity for sustainable development – Beijing June
Notas do Editor
- left, association poplar x wheat in southern France LER = 1,3 large benefits Center association faidherbia with coton and sorghum in sahelian regions Right cocoa agroforest in Costa Rica with managed biodiversity and associated biodiversity (non controled)
- The push-pull technology involves use of behaviour-modifying stimuli to manipulate the distribution and abundance of stemborers and beneficial insects for management of stemborer pests (Figure above). It is based on in-depth understanding of chemical ecology, agrobiodiversity, plant-plant and insect-plant interactions, and involves intercropping a cereal crop with a repellent intercrop such as desmodium (push), with an attractive trap plant such as Napier grass (pull) planted as a border crop around this intercrop. Gravid stemborer females are repelled from the main crop and are simultaneously attracted to the trap crop. Napier grass produces significantly higher levels of attractive volatile compounds (green leaf volatiles), cues used by gravid stemborer females to locate host plants, than maize or sorghum. There is also an increase of approximately 100-fold in the total amounts of these compounds produced in the first hour of nightfall by Napier grass (scotophase), the period at which stemborer moths seek host plants for oviposition, causing the differential oviposition preference. However, many of the stemborer larvae, about 80%, do not survive as Napier grass tissues produce sticky sap in response to feeding by the larvae which traps them causing their mortality. Legumes in the Desmodium genus (silverleaf, D. uncinatum and greenleaf, D. intortum), on the other hand produce repellent volatile chemicals that push away the stemborer moths. These include (E)-b-ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene, semiochemicals produced during damage to plants by herbivorous insects and are responsible for the repellence of desmodium to stemborers. Desmodium also controls Striga, resulting in significant yield increases of about 2 t/ha per cropping season. In the elucidation of the mechanisms of Striga suppression by D. uncinatum, it was found that, in addition to benefits derived from increased availability of nitrogen and soil shading, an allelopathic effect of the root exudates of the legume, produced independently of the presence of Striga, is responsible for this dramatic reduction in an intercrop with maize. Presence of blends of secondary metabolites with Striga seed germination stimulatory, 4′′,5′′,-dihydro-5,2′,4′-trihydroxy-5′′,-isopropenylfurano-(2′′,3′′;7,6)-isoflavanone, and post-germination inhibitory, 4′′,5′′-dihydro-2′-methoxy-5,4′-dihydroxy-5′′-isopropenylfurano- (2′′,3′′;7,6)-isoflavanone, activities in the root exudates of D. uncinatum which directly interferes with parasitism was observed. This combination thus provides a novel means of in situ reduction of the Striga seed bank in the soil through efficient suicidal germination even in the presence of graminaceous host plants in the proximity. Other Desmodium spp. have also been evaluated and have similar effects on stemborers and Striga and are currently being used as intercrops in maize, sorghum and millets.
- Des modèles d’utilisation de systèmes associant verger et moutons sont retrouvés dans la Caraïbe, notamment à Cuba où l’association entre agrumes et ovins est étudiée depuis quelques années. Dans ces systèmes, les moutons sont éduqués selon différentes techniques d’apprentissage pour paître sans abîmer les arbres. Une des techniques consiste en l’utilisation de licols empêchant les animaux de consommer l’écorce et les feuilles. Une technique plus élaborée consiste à pulvériser sur les feuilles d’agrumes un répulsif (chlorure de lithium ou sirop d’ipécacuana) provoquant une aversion pour les feuilles de cette espèce lors de l’installation des animaux. Ils sont ainsi conditionnés à ne pas consommer les feuilles, et transmettent éventuellement ce comportement à leurs jeunes. Plus « simplement », en Martinique, la maîtrise de la couverture végétale des vergers, naturelle (adventices) ou installée (plantes de service), peut aussi être assurée par des moutons, mais, afin qu’ils ne portent pas préjudice à la culture principale, on exploite leur aversion alimentaire naturelle dans une association « judicieuse » avec des Annonacées telles que corossol, cachiman et pomme-cannelle. De même, le pâturage des volailles et des oies en particulier, qui sont plus herbivores que les poulets, plutôt granivores, s’est révélé une méthode efficace pour la maîtrise de l’enherbement en verger de goyaviers.
- - Faune (du micro < 0,2 mm au macrofaune > 4 mm) : Un m 2 de prairie tempérée abrite dans ses 30 cm près de 260 millions d'organismes de la microfaune appartenant à plusieurs milliers d’espèces (biomasse > 1,5 t/ha). Milliers d’espèces de lombrics pouvant représenter jusqu’à 5 t/ha - Champignons et bactéries (jusqu'à 100 millions d’organismes/g. de sol) - Biodiversité végétale avec ses rhizosphères, interface complexe entre les mondes végétal, animal, microbien, fongique et minéral. - L'ensemble des éléments abiotiques constituant le sol sont mobilisés par la biodiversité, qui recyclent également la biomasse morte et les excréments animaux constituant la base trophique des écosystèmes terrestres, l’alimentation minérale des végétaux. Processus biotiques et abiotiques permettant la pédogénèse, la décompaction, la minéralisation, la formation des complexes argile/humus, les symbioses, etc.
- Rappeler la caricature de cette dichotomie