SOIL CARBON DIOXIDE FLUX AND RICE PHOTOSYNTHESIS

概要

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Measurement of CO_2 concentration in air at 25cm below and 100cm above the canopy of a good rice crop indicated that a severe CO_2 deficit occurred around the photosynthetic surface of crop when light intensity was high. Soil CO_2 flux as measured by the soda lime method in a closed system ranged from 3.9 to 5.7g・m^<-2>・day^<-1> under flooded conditions and from 6.0 to 8.6g・m^<-2>・day^<-1> under drained conditions. Cropped soil released more CO_2 than bare soil under both flooded and drained conditions. The estimated contribution of soil CO_2 to gross photosynthesis was 6% for the flooded soil and 7% for the drained soil or a contribution of 9 and 12% to net dry matter production. These results together with other information indicate that atmospheric CO_2 is the most important source of CO_2 in crop photosynthesis, soil CO_2 released into atmosphere is second most important, and soil CO_2 absorbed by plant roots is almost negligible.
社団法人日本土壌肥料学会の論文