Ics of the soil have been described previously [28]. Planting pots (upper

Ics of the soil have been described previously [28]. Planting pots (upper diameter = 19 cm; lower diameter = 14 cm; height = 16 cm) were filled with 2 kg dry soil and turned into a slurry with demineralized water. For planted rice microcosms, in total 48 pots were prepared, 16 pots for the unamended control, and 16 pots each for RS treatment I and RS treatment II. 3687-18-1 supplier fertilizer solution (50 ml of a solution containing per liter: 10 g urea, 7.6 g KH2PO4) was added to each pot as basal fertilizer. For both RS treatments, 10 g powder of RS was added to each pot and mixed thoroughly into the soil slurry. The d13C values of RS added in treatment I and II were 213.0 and 474.7 , respectively. These d13C values were obtained by adding desired amount of 115103-85-0 biological activity 13C-labeled (d13C = 1859.9 ) and unlabeled (d13C = 227.6 ) RS separately into each pot. The 13C-labeled RS was prepared by growing rice plants in the greenhouse until the late vegetative stage. The plants were covered with a 18-L acrylic chamber, 1 13CO2 (final concentration; 99 atom , Sigma, Germany) was added to the headspace, incubated for 5 days (12 h light, 25uC), and then harvested. The unlabeled RS was from rice plant grown in the same manner without feeding on 13CO2. These rice plants were dried and ground to powder. After 3 days of incubation in the greenhouse, all the pots were planted with one 12-day old rice seedling (Oryza sativa var. KORAL type japonica), and were flooded with demineralized water to give a water depth of 5 cm above the soil surface. The water depth was maintained throughout the experimental period. The rice microcosms were incubated in the greenhouse with a relative humidity of 70 , a 12h photoperiod and a 28/22uC day/night temperature cycle. The day of transplantation was taken as day zero. On day 21, a second dose of 30 ml fertilizer solution was added to each microcosm. At each sampling time (day 41, 55, 70 and 90), 12 rice microcosms were sacrificed (4 replicates for control and for each treatment). For unplanted microcosms, the preparation was the same as for planted ones, but without rice plant in the pots. In total, 12 pots were prepared with 4 pots each for the unamended control, RS treatment I and RS treatment II.Samples for the determination of the isotopic signature (d13CH4) of the emitted CH4 were taken in glass containers (100 ml). The first sample was taken directly after closure of the chambers, the second sample 18325633 was taken at the end of the 2-h closure period. The isotopic signature of the emitted CH4 was calculated according to [27]. Pore water samples were collected into Venoject bloodcollecting tubes (Terumo Europe N.V., Belgium) from the rhizosphere (3 cm depth) and bulk (9 cm depth) soil of rice microcosms using Rhizon pore water samplers (Rhizosphere Research Products, the Netherlands). After heavy shaking by hand, the headspace of the tubes was sampled using a pressure lock syringe and directly analyzed for CH4 and CO2 and d13C. The CH4 and CO2 concentration in the soil pore water was calculated as described previously [27]. Plant height, tiller number and aboveground biomass were determined. For dry weight determination, samples were dried for 48 h at 60uC.Production rates of CH4 and CO2 and respective d13C values were determined by collecting soil core samples in rice microcosms on day 41, 55, 70 and 90 of incubation in the greenhouse [27]. After cutting off the rice plant, the surface water layer was removed. Soil cores were taken in each pot.Ics of the soil have been described previously [28]. Planting pots (upper diameter = 19 cm; lower diameter = 14 cm; height = 16 cm) were filled with 2 kg dry soil and turned into a slurry with demineralized water. For planted rice microcosms, in total 48 pots were prepared, 16 pots for the unamended control, and 16 pots each for RS treatment I and RS treatment II. Fertilizer solution (50 ml of a solution containing per liter: 10 g urea, 7.6 g KH2PO4) was added to each pot as basal fertilizer. For both RS treatments, 10 g powder of RS was added to each pot and mixed thoroughly into the soil slurry. The d13C values of RS added in treatment I and II were 213.0 and 474.7 , respectively. These d13C values were obtained by adding desired amount of 13C-labeled (d13C = 1859.9 ) and unlabeled (d13C = 227.6 ) RS separately into each pot. The 13C-labeled RS was prepared by growing rice plants in the greenhouse until the late vegetative stage. The plants were covered with a 18-L acrylic chamber, 1 13CO2 (final concentration; 99 atom , Sigma, Germany) was added to the headspace, incubated for 5 days (12 h light, 25uC), and then harvested. The unlabeled RS was from rice plant grown in the same manner without feeding on 13CO2. These rice plants were dried and ground to powder. After 3 days of incubation in the greenhouse, all the pots were planted with one 12-day old rice seedling (Oryza sativa var. KORAL type japonica), and were flooded with demineralized water to give a water depth of 5 cm above the soil surface. The water depth was maintained throughout the experimental period. The rice microcosms were incubated in the greenhouse with a relative humidity of 70 , a 12h photoperiod and a 28/22uC day/night temperature cycle. The day of transplantation was taken as day zero. On day 21, a second dose of 30 ml fertilizer solution was added to each microcosm. At each sampling time (day 41, 55, 70 and 90), 12 rice microcosms were sacrificed (4 replicates for control and for each treatment). For unplanted microcosms, the preparation was the same as for planted ones, but without rice plant in the pots. In total, 12 pots were prepared with 4 pots each for the unamended control, RS treatment I and RS treatment II.Samples for the determination of the isotopic signature (d13CH4) of the emitted CH4 were taken in glass containers (100 ml). The first sample was taken directly after closure of the chambers, the second sample 18325633 was taken at the end of the 2-h closure period. The isotopic signature of the emitted CH4 was calculated according to [27]. Pore water samples were collected into Venoject bloodcollecting tubes (Terumo Europe N.V., Belgium) from the rhizosphere (3 cm depth) and bulk (9 cm depth) soil of rice microcosms using Rhizon pore water samplers (Rhizosphere Research Products, the Netherlands). After heavy shaking by hand, the headspace of the tubes was sampled using a pressure lock syringe and directly analyzed for CH4 and CO2 and d13C. The CH4 and CO2 concentration in the soil pore water was calculated as described previously [27]. Plant height, tiller number and aboveground biomass were determined. For dry weight determination, samples were dried for 48 h at 60uC.Production rates of CH4 and CO2 and respective d13C values were determined by collecting soil core samples in rice microcosms on day 41, 55, 70 and 90 of incubation in the greenhouse [27]. After cutting off the rice plant, the surface water layer was removed. Soil cores were taken in each pot.