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Th2_Climate Change in the Senegal River Valley and implications for rice cropping systems
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Th2_Climate Change in the Senegal River Valley and implications for rice cropping systems

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3rd Africa Rice Congress …

3rd Africa Rice Congress
Theme 2: Rice Intensification and diversification
Mini-symposium: determinants of agricultural productivity in Africa's rice based-systems
Author: Balde and Muller

Published in: Technology

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  • 1. Climate Change in the Senegal River Valley and implications for rice cropping systems BALDE A.B. (AfricaRice); MULLER B. (Cirad/AfricaRice); VAN Oort P.(AfricaRice); NDIAYE O. (ANACIM); STUERZ S. (Hohenheim University); SOW A. (AfricaRice); DIACK B.S. (SAED); DINGKUHN M. (Cirad/IRRI) Study funded by ANR ESCAPE and CCAFS
  • 2. Introduction (1) • Irrigated rice is important crop in Sahel • More than 70 000 ha in Senegal River valley • Rice double cropping possible Sterile spikelets Climate and sowings • Cold (November-March) and hot (April-October) extreme temperatures are risks -> sterility • Recommended sowing periods were elaborated in 90s (Dingkhun and al., 1995) based on 1950-80 climate data and RIDEV1 model • 15 Feb - 15 March for Dry Season • 01 July – 15 August for Wet Season
  • 3. Introduction (2) RIDEV1 1950-80 sterility analysis (Dingkhun, 1995) BUT farmers say … % Sterility Saint-Louis Sterility (cold) Rosso « sowing date are more and more out of the recommended sowing windows, and that works : even sowing in September farmers get good yields! » « It looks like the climate have changed » Questions : Did farmer’s practices change (% of farmers)? Why ? Due to climate ? others constraints ? Matam Did climate change ? How ? What can we learn from those evolutions ? Tillaberi Sowing date 1 year Sterility (heat) Are recommended sowing periods still valid ? How to protect farmers against climatic risks ?
  • 4. Objectives Final objective is to define the most adapted sowing windows for recommended irrigated rice varieties of Senegal River Valley (and Niger River Valley in Mali) in order to reduce climate risks and then maximize production, and to assess the “residual” risks related to those sowing windows ; - for “present” climate - also for “future” one using data coming from climatic scenario Second main objective is to assess if cropping systems have changed in the last years and if it is the case, to understand why ? Third main objective is to have a crop model (or several) able to correctly simulate developments and yields of recommended irrigated rice varieties in Senegal River Valley (and Niger River Valley in Mali) Fourth: capacity building for production and management of climatic risks Fifth : to elaborate insurance systems based on scientific results (risks analysis)
  • 5. Material and Methods Focus-groups and surveys: to understand possible changes in farmer’s practices and their constraints, and their eventual evolutions during the last years to understand farmers climate perception Climate (temperature) analysis : Podor (16.35N/15.02W) temperature data from 1950 to 2011. Modeling analysis : RIDEV V2 to assess through RIDEV2 crop model simulations the impacts of climate since 30 years for different sowing dates -> Case of Sahel 108 cultivar ; Podor weather data (Tmin, Tmax, Mean Hum, and Rg) from 1950 to 2010 Sowing every 15 days RIDEV2 : to simulate Phenology and Heat & cold sterility Calibration/Validation Simulations
  • 6. Results (1) : from focus and surveys  Due to several constraints (delay for inputs, credit, machines) many farmers are sowing later than before, i.e. outside the recommended sowing windows : this is particularly the case for wet season cropping (July/August -> November)  All interwied farmers mentioned difficulty and delay to get inputs, credits and machines as their main constraint  Some farmers having sowed late (September) obtained good results  Many farmers are now sowing regularly at the beginning of September and have good yields since few years.  Exception 2011: “bad yields” (farmers words) for those late sowing  “Since 2000 yields are decreasing” ; except in the dry season of 2008 with 7t/ha (exceptional year)  “Dry season yields are better than wet season ones” (for 90% of farmers)
  • 7. Results (2) : from focus and surveys  Farmers notice climate “changes”: on average 94.5% and 72% of interviewed farmers say respectively that rainfall and temperature pattern have changed.  “the cold period shifted (delayed) by about 1 month” : October/NovemberFebruary/March -> November-March/April  “the cold comes latter”, “excepted in 2011 it came as before”  “the February-April period is very hieratic, with small cold and hot periods”  “rainfall increased in the last 5-7 years, except in 2011” (Podor rainfall data shown an annual average of 175, 200 and 270 mm respectively between 1980-1989, 1990-1999 and 2000-2010)
  • 8. Results (3) : temperatures analysis 42 41 40 39 38 37 36 35 34 33 32 31 30 1950-1980 1970-1990 Month TMAX +1°C to +3°C / reference period 1950-1980 but quite similar than 1990-2000 1 2 3 4 5 6 26 24 22 20 18 16 14 12 10 8 6 4 2 0 7 8 9 10 1990-2000 2001-2011 11 1950-1980 1970-1990 1990-2000 2001-2011 2 3 4 5 6 7 8 9 10 11 12 1950-1980 1970-1990 Month TMIN +1°C to +2°C / reference period 1950-1980 but quite similar than 1990-2000 1 12 Days TMAX>40°C more than reference period 1950-1980 but quite similar than 1990-2000 1 26 25 24 23 22 21 20 19 18 17 16 15 14 2 12 11 10 9 8 7 6 5 4 3 2 1 0 3 4 5 6 7 8 9 10 11 1990-2000 2001-2011 12 Days TMIN<14°C less than reference period 1950-1980 but quite similar than 1990-2000 1950-1980 1970-1990 1990-2000 2001-2011 1 2 3 4 5 6 7 8 9 10 11 12
  • 9. Results (4) : 2011 temp. analysis 35 34 33 32 31 30 29 28 27 26 25 24 23 22 TMEAN 2011 2006-10 2000-10 1990-99 1 4 7 10 13 16 19 22 25 28 31 26 25 24 23 22 21 20 19 18 17 16 15 14 TMIN 2011 2006-10 2000-10 1990-99 34 1 4 7 10 13 16 19 22 25 28 31 34 Oct.-Nov. 2011 is rather hot ! Only end of December is colder than other years .. So ..??? TMIN <18°C 11 10 9 TMIN <14°C 6 5 8 7 2011 6 2006-10 5 4 2011 2006-10 3 2000-10 2000-10 4 1990-99 3 2 2 1990-99 1 1 0 0 1 4 7 10 13 16 19 22 25 28 31 34 0 3 6 9 12 15 18 21 24 27 30 33 36
  • 10. Results (5) : model validation (Ndiaye, Fanaye) (b) Flowering 140 120 100 80 60 Maturity 60 Model parameters (Ndiaye site, MD): Tbase=10.6°C Topt=31.7°C SumBVP=748 SumRPR=400 SumMATU=409 CritsterCold1=10.6°C CritsterCold2=18.7°C CritsterHeat=33°C 80 Simulated 160 y = 1.02x + 1.087 R² 1200.845 140 = 100 110 60 (c) Sterility is underestimated by the model (with present calibration; can be improved) 80 100 Sterility 100 90 80 70 60 50 40 30 20 10 0 0 y = 1.047x - 1.289 R² =140 0.823 160 120 60 Observed Simulated Simulated (a) 20 40 Observed y = 0.572x - 1.219 R² = 0.473 60 Observed 80 100
  • 11. Results (6) : simulated cycles and sterilities Crop duration decreased (- 5-10 days) but variable through sowing dates (from 90 to 137 DAS) Compared to 1950-1980, cycles are shorter in recent years For both Wet and Dry Season (WS, DS) sterility (out of recomandated calendar) globally decreased However differences are small For 15 September small sowing sterility difference exists It is still very dangerous to sow after this date
  • 12. Results (7) : Focus on 15 Sept sowing date (Simulations from 1980 to 2010) The evolution of sterility (for 15 Sept sowing date) is going down through years Same with DAS to Flowering In the past flowering period met low temperature that make high Stercold2
  • 13. Conclusions (1) Present climate is different than during the reference period (1950-80) used for elaboration of sowing recommendations with RIDEV1 : temperatures clearly increased ; less cold days But it seems that the climate (at least Temp) is already “different” since 20 years .. not only from 2000 as farmers say (“it recently changed”) And up to now we don’t understand the specificity of 2011 ? We need more data to check climate evolution for all SRV (we are waiting for St Louis, Matam, Bakel data) Sterility is underestimated by the model and quite low Due to temperatures increase cycles are shorter (- 5-10 days) now (no “genetic change” in Sahel 108)
  • 14. Conclusions (2) Cold stress risks are lower, particularly for late 15 September sowing : it seems possible to sow up to this date but not recommended to sow after this date Risks due to high temperatures might be higher : must be analyzed with more accuracy We need to check more the model functioning (we have several fields and experiments data) We need to go back to farmers with simulations results in order to improve our understanding If climate seems to be more favorable, why farmers say yields are lower ? …
  • 15. Conclusions (3) Still many work to do to clearly understand the evolution of things Once we will be sure that our model functions well, we will see how to elaborate new sowing recommendations and how to develop temperatures based indicators for insurance
  • 16. Thank you for your attention! Alpha Bocar BALDE a.balde@cgiar.org

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