It was confirmed that elevated CO2 concentrations in the root
zone associated with elevated soil water contents suppressed growth and tuberous root development of sweet potato. The
growth and tuberous root yield of sweet potato in the soil ridge
was significantly affected by irrigation frequency. When producing
sweet potato, it is important to manage water supply to ensure
sufficient water contents and low CO2 concentrations in soil. As
an application of the soil ridge culture method with the bottom
irrigation system, it was expected that tuberous root production of
sweet potato will be increased by controlling the soil ridge height
to keep an enough distance from the water table to the soil surface
for maintain 10–15% of volumetric water contents and low CO2
concentrations in root zone soil.