Soil carbon sequestration to address food security and climate change in Africa

Transcription

1 Soil carbon sequestration to address food security and climate change in Africa SALL Saïdou Nourou University of Gaston Berger, Saint-Louis, SENEGAL Razafimbelo Tantely, Badiane Ndour, Aholoukpe Hervé, Hien Edmond, Olina Jean-Paul, Koné Armand,, Brossard Michel, Razakamanarivo H., Adoum Abdouraman, Bernoux Martial Sponsor : Département ECOBIO - IRD Ecologie, Biodiversité et Fonctionnement des Ecosystèmes Continentaux

2 Contexte Food security : main challenge of African countries Soil degradation Demographic pressure En Afrique de l Ouest ( ) X 2 Climate change impacts Increase of the pressure on soil Need for African countries to link soil productivity, food security and soil C sequestration

3 Key facts and figures Why Soil Carbon? 95% of our food is directly or indirectly produced by our soils [FAO April 2015: Healthy soils are the basis for healthy food production] 2-3 times more carbon in soil organic matter than in atmospheric CO 2 [IPCC, 2013] 1.4 billion metric tons carbon could be stored annually in agricultural soils, equivalent to a storage rate of 0.48 % per year in top soil [after IPCC, 2007, 2014] million metric tons additional grains could be produced in developing countries by storing an additional ton of carbon per ha in soil organic matter [Lal, 2006]

4 What solutions? Promoting sustainable agriculture based on optimum management of Soil Organic Matter Managing Soil Organic Carbon Soil organic carbon = Soil fertility, Soil productivity Soil organic carbon = soil C sequestration, mitigation of GHG emission

5 Mobilization of African and European researchers to promote soil carbon sequestration for a sustainable management of soil fertility and productivity To replace soil and soil carbon as the central component of sustainable agricultural systems 11 African and European countries (for 21 teams) Algeria Benin Burkina Faso Cameroun Ivory Coast Mali Madagascar Morocco Senegal Tunisia France Carbone du Sol pour une Agriculture durable en Afrique

6 How to sequester more?

7 SOC (Mg.ha -1 ) Examples of sustainable practices that enhancing soil carbon sequestration 1) Increasing management of Oil Palm in Benin - To compare SOC under natural forest and cultivated systems - To estimate legume cover effect on carbon storage in OP Palm cultivation: ha T of Oil Palm per year Increasing management : use of cover crop (pueraria javanica) Cover effect * Akpadanou, Benin * DC1 = Mg/ha/an Ferralsol Depth 0-35 cm Sandy Soil 20 years of cultivation DC1 = 220 * Djégui et al., 1992 The use of cover crop (pueraria javanica) induce an increase of soil carbon storage of 220 when compared with oil palms without cover crops. 7

8 Examples of sustainable practices that enhancing soil carbon sequestration 2) Zaï in Burkina Faso Traditional practice used in Sahelian area to restore degraded soils «To wake up early» A micro-catchment system A local supply of organic matter 8 Photos : Hien E. Roose et al 1999

9 Examples of sustainable practices that enhancing soil carbon sequestration 2) Zaï in Burkina Faso Soil Organic Carbon in Zaï system (Masse et al., 2011) SOC tended to be higher in the zaï holes SOC increased with the duration No significant difference in the SOC of the topsoil (0 10 cm) under conventional tillage and in zaï plots due to the high variability in the results 9

10 Examples of sustainable practices that enhancing soil carbon sequestration 3) Use of organic amendment in Madagascar Manure Manure-Urban waste- Compost Ferralsol, clay soil 8 years of cultivation Depth 0-30 cm Compost DC3 = DC3 = 103 DC1 = DC2 = DC1 = 21 DC2 = 86 MgC/ha/an Urban waste Razafimbelo et al. No significant increase of SOC, the use of amendment led to a maintain of soil organic carbon content on the same level

11 A. Koné (UNA) Examples of sustainable practices that enhancing soil carbon sequestration 4) Conversion of forest to farmland in Ivory coast A 0-40 cm Forêt Savane Ferralsols Igname / Chromolaena odorata B For C.o. (For) Sav C.o. (Sav) D après Kassi et al, 2017

12 SOC (Mg.ha -1 ) Examples of sustainable practices that enhancing soil carbon sequestration ) Agroforestry system in the East coast of Madagascar * DC = MgC/ha/an DC = 200 * * Razafimbelo et al System : Cloves + Rice - Simple : under 200 Cloves/ ha - Complex : 200 to 400 Cloves / ha 0 Slash Burn Slash Agroforestry 12 (complex) Agroforestry (simple) 24 years of cultivation Depth 0-40 cm Nitisol, Sandy loam - SOC storage in Agroforestry systems are accounting for an increase of SOC was quite similar for complex and simple agroforestry.

13 Some concluding notes? - SOC were very different according the systems - High spatial variability affect the significance of the results - The use of approaches synchronic vs diachronic according to the existing situations Challenges for the assessment of sustainable practices impact on C? - Consider the saturation of soil : f(type of soil) - Develop long-term observatories (Synchronic vs Diachronic approach) - Establishment of baseline/reference - Implementation of an harmonize methodology for soil carbon measurement (methods, depth ) 13

14 Thanks to my sponsor : Thank you for your attention saidou-nourou.sall@ugb.edu.sn Département ECOBIO Ecologie, Biodiversité et Fonctionnement des Ecosystèmes Continentaux and team of the event