Canopy scale CO2 exchange and productivity of transplanted paddy and direct seeded rainfed rice production systems in S. Korea

•Higher GPP, (β+γ)1500, aboveground biomass, specific leaf weight, leaf N content and quantum yield in rainfed rice.•PAR determined the daily fluctuations in GPP while seasonal trends were due to GLAI and α.•Shifts in C allocation improved water uptake and avoided water stress with a slight compromise in yield for rainfed rice.•Rice hybrid Unkwang maintains productivity under rainfed agriculture in the absence of drought.