Biomass production and nutritional levels of berseem (Trifolium alexandrium) grown under elevated CO2

There is little available information about the effect of elevated CO2 on the growth and mineral nutrients of fodder crops. To investigate the changes in vegetative biomass and nutrient concentration of berseem (Trifolium alexandrium L.), an important forage legume, was grown in ambient (360 μl l−1) as well as elevated (600 μl l−1) CO2 conditions from germination onwards in open top chambers. Elevated CO2 increased the leaf size, plant height and fresh and dry mass of shoots. There was more partitioning of photosynthates towards the growth of new branches than towards the growth of leaves. Leaf nitrogen, soluble proteins, calcium, iron and nitrate reductase (NR) activity decreased in elevated CO2 while leaf carbon and phosphorus contents increased. The results suggest that berseem grown in elevated CO2 throughout the crop season can produce more fodder in less time. The study concludes that elevated CO2 may increase the fodder production by 30–35% but will adversely affect the nutritional quality of the forage due to reduction in nitrogen, protein, calcium and iron concentration in leaves on a unit dry weight basis. On a unit area basis, however, there will be an increase in total nutrient content, including nitrogen, due to increased fodder biomass in elevated CO2.