Growth and yield responses of field-grown sweetpotato to elevated carbon dioxide

Root crops are important in developing countries, where food supplies are frequently marginal. Increases in atmospheric CO2 usually lead to increases in plant growth and yield, but little is known about the response of root crops to CO2 enrichment under field conditions. This experiment was conducted to investigate the effects of CO2 enrichment on growth and yield of field-grown sweetpotato [Ipomoea batatas (L.) Lam.]. Plants were grown in open-top chambers in the field at four CO2 levels ranging from 354 (ambient) to 665 μmol mol-1 in two growing seasons. Shoot growth was not affected significantly by elevated CO2 Yield of storage roots increased 46 and 75% at the highest CO2 level in the 2 yr. The yield enhancement occurred through increases in the number of storage roots in the first year and through increases in both the number and size of the storage roots in the second year. Storage-root/shoot ratios increased 44% and leaf nitrogen concentrations decreased by 24% at the highest CO2 level. A comparison of plants grown in the open field to plants grown in open-top chambers at ambient CO2 concentrations indicated that open-top chambers reduced shoot growth in the first year and storage-root yield in both years. These results are consistent with the majority of CO2-enrichment studies done on pot-grown sweetpotato.