Tropical and Subtropical Forage Grasses in Agrivoltaic Systems: Physiological Responses, Agronomic Management, and Research Gaps

Solar photovoltaic energy is expanding rapidly, and grassland is repeatedly identified as the land use best suited to solar co-location. However, the tropical and subtropical C4 forage grasses that underpin livestock production across most of the Global South, Urochloa/Brachiaria, Panicum/Megathyrsus, Cynodon, and Pennisetum, are absent by name from the largest systematic reviews and meta-analyses of agrivoltaic evidence published to date, despite forages being the largest crop category in the most comprehensive of these syntheses. This review argues that this is not a general evidence gap but a precise one: two independently mature areas in the literature, silvopastoral shade-response physiology and agrivoltaics pasture research, have never been directly crossed. We synthesize microclimate mechanisms specific to photovoltaic panel shading with no documented counterpart in tree canopy systems, genus-specific shade-response evidence from silvopastoral research, nascent evidence on animal performance under real photovoltaic arrays, a theoretical framework for the shade × water-stress interaction, arrangement design as a management variable, nitrogen and water management, and land-use efficiency and adoption barriers. We close by proposing a concrete, methodologically precedented experimental agenda and adapting multi-level phenotyping and field factorial designs already validated in the adjacent literature to test tropical C4 forage genera under authentic photovoltaic shade for the first time.