安定同位体を用いた開放系大気CO2増加実験における植物由来炭素の水田土壌への移行評価

Effects of Free-Air CO2 Enrichment on Plant-derived Carbon Input in Andosol and Ultisol Paddy Soil as Evaluated by Carbon Isotope Changes

[ABSTRACT] Increasing the concentration of atmospheric carbon dioxide （［CO2］） generally results in enhanced rice production. On the other hand, paddy soils can mitigate the increase in ［CO2］ by sequestering organic carbon （C）, but these effects have not been quantified in the field. We applied a mass balance method to estimate the amount of C translocation from planted rice to the soil under ambient （control） and free-air CO2 enrichment （FACE） conditions by cultivating rice plants （Oryza sativa L. cv. Akitakomachi） in pots filled with two types of soils: Andosol and Ultisol （high and low organic C, respectively）. The ［CO2］ in the FACE treatments was maintained at approximately 200 µmol·mol−1 higher than that under ambient conditions （δ13CO2 was about −8 ‰） by fumigation with pure industrial CO2 （δ13C was about −38 ‰）. The results showed that rice growth increased in the FACE treatment using both Andosol and Ultisol, although the effects were not statistically significant. Root δ13C with Andosol was −27.9 ‰ and −35.9 ‰ under ambient and FACE conditions, respectively, and −27.7 ‰ and −36.8 ‰ with Ultisol, reflecting differences in the δ13C of available CO2. In the same manner, soil δ13C values after rice cultivation under ambient and FACE conditions in the Andosol surface （0–5 cm） were −22.3 ‰ and −22.5 ‰, respectively, and −16.2 ‰ and −16.7 ‰ in Ultisol. Based on these changes, the estimated total C input from rice to soil （sum of surface and subsurface, 5–16 cm） was 0.4 to 1.6 t·ha−1 for Andosol and 0.04 to 0.05 t·ha−1 for Ultisol. These results reveal that elevated atmospheric ［CO2］ did not have significant effects on C input during one cropping season of rice, due to a relatively small response of rice growth and increased decomposition activities of soil microbes. The possibility of longer term C sequestration by paddy soils should be investigated further.

https://opac.ll.chiba-u.jp/da/curator/105023/

https://opac.ll.chiba-u.jp/da/curator/105023/S18808824-72-P019.pdf

千葉大学大学院園芸学研究科

Chiba University. Graduate school of Horticulture

Journal Article

1880-8824

AA12123127

食と緑の科学 = HortResearch

72

19

28

2018-03-31

https://doi.org/10.20776/S18808824-72-P19

jpn

publisher

HortResearch