Atmospheric carbon dioxide enrichment enhances plant growth and development and may alter the nutritive value of grasses. The objective of this study was to evaluate growth, biomass partitioning and nutritive value of Kyasuwa under combinations of atmospheric CO2 concentrations, watering and fertilization treatments. Plants were grown in two greenhouse chambers; with ambient (aCO2; 400 ppm) and elevated CO2 (eCO2; 950 ppm), two watering and three fertilization regimes. Elevated CO2 reduced stomatal conductance by 40%, root to shoot ratio by 8%, leaf to stem ratio (L:S) by 3%, protein content by 14% and Acid Detergent Lignin (ADL) by 23% with no significant changes in total biomass and C/N ratio however, slight increases in leaf area (2%) and Acid Detergent Fiber (ADF) by 4%. Higher fertilization resulted in increased biomass parameters only in well-watered plants while; a lower C/N ratio was recorded with higher fertilization. The L:S ratio was decreased with fertilization while ADL was increased at higher fertilization in well-watered plants. Interactive effects were recorded for ADF content and shoot height. Future eCO2 will be unfavorable to Kyasuwa growth and biomass production making them less competitive with a reduced nutritive value in drought prone and infertile soils
