We contribute to the understanding of technology adoption decisions by complex farm households in the Sudano-Sahelian region of West Africa, where production is organized collectively under the leadership of a senior head who also allocates individual fields to members. Farm families span generations and encompass several nuclear households. We examine the nature of the linkage between fertilizer use decisions on collective and individual plots based on a conceptual model of intra-household bargaining that enables us to draw inferences about efficiency of input allocation. Although the share of individual maize plots receiving fertilizer is lower, use rates on maize tend to be higher than on collective fields. Adoption of fertilizer on a collective plot contributes to a 0.32 rise in adoption probability on an individual plot, but the converse is not true. The marginal effect of application rates on collective plots is positively associated with intensity of use on individual plots but of a magnitude consistent with inefficiency of resource allocation. Determinants of adoption differ between individual and collective fields, and between the decision to use fertilizer and the intensity of use. Findings have implications for the design of extension programs and policies to support agricultural intensification in the region.