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Rheinischen Friedrich-Wilhelms-Universität Bonn (2019)

Rice yield gaps in West Africa

Niang, Abibou

Titre : Rice yield gaps in West Africa

Auteur : Niang, Abibou

Université de soutenance : Rheinischen Friedrich-Wilhelms-Universität Bonn

Grade : Doctor of Agricultural Sciences (Dr. agr.) 2019

Résumé
Rice is a staple food for many countries in Africa but the production has never satisfied the demand which largely depends on imports. Therefore, more efforts are needed for raising yield in order to reduce the gap between potential and actual farmers’ yields. To increase yield, improved management options are to be considered. Thus, this thesis has estimated the range of yields and yield gaps at three rice production systems in West Africa across climatic zones, the affecting factors and has explored management options to reduce the gap between potential and actual farmers’ yield. Field surveys were carried out between 2012-2014 in 22 sites located in eleven West African countries covering the main production systems and the main climatic zones. Management practices were recorded through interview, crop status from field observations and yield recorded at harvest. In central Benin, Nitrogen use efficiency was estimated at different field water status using experimental and farmer’s practices’ fields. Finally yield gain was estimated after implementation of GAP in selected farmers’ fields. Boundary function was used to estimate attainable yield. Random forest evaluated the importance of variables explaining yield and yield gap variability. Average yield was 4.1, 2.0, and 1.5 t/ha in irrigated lowland, rainfed lowland, and rainfed upland rice production systems, respectively, with maximum attainable yields of 8.3, 6.5, and 4.0 t/ha. The factors affecting yields were specific to each production system. Yield gaps between potential/water limited yields and actual farmers’ yields ranged from 1.1 to 10.2 t/ha and from 3.5 to 10.3 t/ha in irrigated and rainfed systems, respectively. Farmers’ yield was 27-51% of potential yield at optimum sowing date in irrigated system, and 17-22% of water limited yield at optimum sowing date in rainfed systems. In irrigated system, 34% of the yield gap was attributed to weeds, N fertilizer application rate and crop establishment methods. In rainfed systems, 30% of this gap was explained by rice variety, field hydrology and weed infestation at maturity stage. The implementation of GAPs in farmers’ fields reduced the average yield gaps between 13 and 25% in irrigated system and between 20 and 42% in rainfed lowland system. These results suggest that there is a large scope for increasing rice yield in West Africa. There is a need for site-specific decision support guide including targeted GAPs for an efficient use of the available farmers’ resources.

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