New technologies to save water for irrigated rice in the Sahel Michiel de Vries, Vincent Bado and Abdoulaye Sow Africa Rice Center (WARDA) Sahel Station - Senegal Africa Rice Congress 31 July – 4 August 2006, Dar es Salaam, Tanzania

80% of rice production in Senegal is irrigated. In irrigation agriculture in the SRV, water accounts for 25% of production costs Improving water use efficiency will reduce costs and improve production efficiency Water-less or aerobic rice can save water (Bouman et al a, b), and is grown under saturated soil conditions, without standing water and without water stress. Introduction Back ground

Problem definition Hypothesis: “Water-less rice can be beneficial for farmers is the Senegal River Valley” Issues to be addressed:  Salinity and high temperatures may be a problem in the Sahel  Weeds may form an important constraint  Genetic material needs to be adapted to new conditions  Yield levels To this end an on-station experiment was done Introduction

Irrigation treatments: (main plot) –Completely aerobic; –Aerobic until PI, then flooded; –Flooded until PI, then aerobic and –Completely flooded Weed control treatments: (sub-plot) –Herbicide applied at 21 DAS; –Herbicide applied at 35 DAS and –no herbicide Methods Treatments

Measurements taken –Volume water irrigated –Water and salinity level in plots –Weed population –Plant growth data –Yield components Methods Measurements

Results Plot water level

Flood water salinity Results Threshold value 3.5 mS/cm

Treatment Irrigation (mm) Rel. water use Aerobic139060% Aerobic- Flooded207090% Flooded- Aerobic152066% Flooded % Results Volume water applied

TreatmentYield (kg/ha) Water Prod. (kg rice/mm irrigation) Aerobic4960 b 3.56 Aerobic-Flooded5490 b 2.65 Flooded-Aerobic6470 a 4.25 Flooded6670 a 2.90 Results Effects of water treatment Same letters are not different according to LSD, α=0.05

Effects of Herbicide treatment TreatmentYield (kg/ha)Tiller/m2 maturity Herb. 21 DAS6990 a 2290 a Herb. 35 DAS6760 a 2310 a No herb.3940 b 1760 b Results Same letters are not different according to LSD, α=0.05

Rice yield (kg/ha) TreatmentHerb. 21 DASNo herbic. Aerobic6200 b 2700 d Aerobic-Flooded6960 ab 2890 d Flooded-Aerobic7160 ab 5080 c Flooded7640 a 5100 c Results Water x Herbicide interaction Same letters are not different according to LSD, α=0.05

Conclusion Under complete aerobic: 25% yield loss compared to flooded, 40% water saving Under flooded-aerobic system no sig. yield loss, 34% water saving Strong herbicide x water treatment interaction Opportunities to save on water! Conclusion

On-station: –In-depth research N x Weed reactions on irrigation –Varietal screening of 42 advanced lines (20 NERICAs) On-farm: –Collaboration with National partners –Sites along Senegal River Socio-economic study Conclusion Next steps

Thank you, Merci, Dieuredieuf, Asante sana ! Special thanks for technical assistance to: Mandieye Top, Gougna Gaye & Malick Sarr