Delivering nutrient management impact through farmer-centric research: a systematic review of innovation systems in African smallholder systems - Ivan S. Adolwa; Shamie Zingore; James Mutegi; Matthew McNee; Bolaji A. Akorede; Denver Masidza; T. Scott Murrell; Samuel Mathu Ndungu; Eileen Nchanji; Simon Cook; Thomas Oberthür (Agricultural Systems, 2025)