Improved soil fertility and weed management is profitable for irrigated rice farmers in Sahelian West Africa

Gains in yield and profitability of irrigated rice (Oryza sativa L.) in the Senegal river region resulting from improved fertilizer and weed management practices were studied in collaboration with farmers' organizations, national research institutes and fanners, The profitability of different fertilizer and weed management treatments was compared to farmers' practice using partial budgeting techniques and the net benefit of all treatments was estimated. Improved fertilizer management increased grain yield by 0.9 t ha(-1), while the recommended weed management resulted in a yield increase of 1.0 t ha(-1). The effect of recommended management practices was additive and gave a mean yield increase of 1.8 t ha(-1) compared to farmers' practices. Principal weed species in rice were Echinochloa colona (L.) Link, Diplachne fusca (L.) P. Beauv. ex Stapf, Sphenoclea zeylanica Gaertner, Bolboschoenus maritimus L,. Schoenoplectus senegalensis (Steudel) Raynal, Cyperus iria L, and Cyperus difformis L, Indications of propanil-resistant E. colona were found. Weed infestation was severe and weed biomass comprised between 24 and 49% of the combined biomass of weeds and rice at panicle initiation. Average losses in rice yield caused by weeds were 0.56 t ha(-1) per 10% of relative weed biomass. The value/cost ratios were between 2.1 and 4,6 for the improved treatments, and improved soil fertility and weed management resulted in an increase in net revenues of 40-85% compared to farmers' practice. (C) 2000 Elsevier Science B.V. All rights reserved.