Carbon release from rice roots under paddy rice and maize–paddy rice cropping

摘要: Abstract Crop rotations encompassing flooded rice and an upland crop are commonly found in large parts of South East Asia. However, also farmers Southeast Asia increasingly switch from double-cropping paddy to one non-flooded crop–such as maize–in the dry season. We hypothesized that introducing maize (maize–paddy rice, M-MIX) into a double (R-WET) cropping system will increase carbon (C) release roots rhizosphere dissolved soil C pool. To test this hypothesis we assessed kinetics by plants hydroponic greenhouse experiment, used these data for interpreting their field experiments using 13C pulse labeling plants. In observed released labeled organic (DOC) 21 days with mean residence time (MRT) 19 after exposure 13CO2 pulse. The MRT inorganic (DIC) was only 2 days. increased excess up 0.7 ± 0.2 mg 13C kg−1 R-WET 0.9 ± 0.3 mg kg−1 M-MIX. signature bulk remained unaffected. DOC concentrations were significantly higher than M-MIX during mature grain stage Nevertheless, transiently 0.5 μg L−1 13 cm depth three lysimeters previously cropped (M-MIX), while no detected 60 cm both treatments. contrast, DIC 42.4–93.1 μg L−1 few 53–66 Considering results suggests rapid mineralization rhizodeposits effective transient storage CO2 produced respiration water.