Table 1.
Soil chemical and physical properties of study area, Chonnam National University research farm, Gwangju, S. Korea.
Fig 1.
Climate conditions and rice growth during the monsoon 2013.
(a) Daily averages of windspeed (ms-1) and relative humidity (%); (b) daily averages of air temperature (°C) and radiation (Mjm-2s-1); (c) daily total rainfall (mmd-1) and daily average volumetric soil water content at 5cm depth (m3m-3); (d) daily LAI of paddy (solid line) and rainfed (dashed line); lines represent simulated LAI and circles represent measured LAI (Black circle = measured LAI of paddy, white circle measured LAI of rainfed rice, n = 9, mean values ± SD).
Fig 2.
Seasonal carbon and water fluxes of rainfed and paddy rice: daily carbon fluxes of (a) rainfed rice; (b) paddy rice (simulated gross primary production, black line; measured gross primary production, black circle; simulated ecosystem respiration, red dashed line; measured ecosystem respiration, red triangle; simulated net ecosystem exchange, black dotted line; chamber measured net ecosystem exchange, white circle); daily water fluxes of (c) rainfed rice and (d) paddy rice(simulated daily evapotranspiration, blue line; chamber measured evapotranspiration, gray circle, simulated transpiration, green line; evapotranspiration minus transpiration (evaporation), blue shaded area) (n = 3, mean value ± SD for measured fluxes).
Fig 3.
Seasonal change in the ratio of transpiration to evapotranspiration (T/ET) and in soil water content: Change in T/ET of rainfed rice (black dashed line) and paddy rice (green straight line) along with change in soil water content at 5 cm (white triangle = rainfed rice, green diamond = paddy rice).
The ratio of transpiration to evapotranspiration (T/ET) was calculated based on simulated daily T and ET of monsoon 2013. T/ET less than zero and greater than one are not shown in the figure.
Fig 4.
Contribution of soil and crop respiration of paddy and rainfed rice.
Ecosystem respiratory flux partitioning of paddy and rainfed rice was done based on dark chamber measured soil respiration (Rsoil, Solid red) and dark chamber measured crop respiration (Rpt). Measurements were carried out during seedling, tillering, heading and maturity stage (n = 3–4, mean value ± SD).
Fig 5.
Effects of respiratory carbon loss and evaporative water loss over water use efficiency.
(a) Yield/ET of rainfed rice (light yellow) was higher than paddy rice(dark green) (F = 10.61, p ≤ 0.05)but NEE/ET were not significantly different, (b) Yield/T was not significantly different between paddy and rainfed rice (F = 0.14, p = 0.75) highlighting the higher evaporative loss in paddy rice; (c) Lower GPP/ET of paddy rice due to its higher evaporative water loss (F = 9.96, p ≤ 0.05); and higher GPP/ET of rainfed rice due to its higher respiratory carbon loss (F = 25.41, p ≤ 0.01).(One way ANOVA followed by TukeyHSD posthoc test was applied to access WUE differences between paddy and rainfed (n = 3–12, mean value ± SD); different small letters denote significant differences among paddy and rainfed rice within each panel (a to f) while different capital letters denote significant differences among different water use efficiencies (A to G).
Fig 6.
Seasonal carbon and water balance of paddy and rainfed rice.
Seasonal cumulative gross primary production (GPP), net ecosystem exchange (NEE), ecosystem respiration (Reco), evapotranspiration (ET), transpiration (T) and grain yields were used in this schematic representation. All data except the grain yield (grain yield: n = 6 ± SD) were calculated based on the daily simulation presented in Fig 2. Crop growing season was 120 days (sowing to harvest).