| Budget Amount *help |
¥8,600,000 (Direct Cost: ¥8,600,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2003: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2002: ¥3,600,000 (Direct Cost: ¥3,600,000)
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| Research Abstract |
Green house experiments were conducted in order to analyze C and N dynamics in soil, including organic nitrogen uptake by rice plant. For tracing C and N in soil, ^<13>C and ^<15>N labeled materials with low or high molecular weight were used such as ^<13>C-glucose, ^<15>NH4CL and ^<13>C and ^<15>N dual-labeled rice straw compost, bacteria, and fungi In experiment 1, the recovery percentages of rice uptake of ^<13>C from glucose applied into the soil at the basal fertilization were 1.8 % in root, 0.8 % in leaf and stem, and 0.9% in ear, indicating paddy rice absorbed a significant amount of C by root. On the other hand in nitrogen, higher recovery was observed as following, root (9.2 %), leaf and stem (16.2 %), and ear (27.2 %). The half life period of ^<13>C at early and mid growth stage was 16 and 210 days, respectively. It indicated that the ^<13>C in glucose was quickly absorbed and metabolized by soil microbes but the secondary metabolic products had a lower turnover rates. In experiment 2, recovery rate of plant uptake of C from rice straw compost were 2.23 % in root, 1.35 % in leaf and stem, and 1.16 % in ear. In experiment 3, ^<13>C in bacteria (Bacillus subtilis) applied was distributed to 2.13 % in root, 7.41 % in leaf and stem, and 4.94 % in ear. Higher distribution was observed in ^<13>C in fungi (Aspergillus nigar) as 19.3 % in root, 2.61 % in leaf and stem, and 24.0 % in ear. These results indicate that rice plant took up C more favorably at 4-13 times from soil microbes than glucose or rice straw compost. Therefore, soil microorganisms possibly play not only a role of decomposer but also that of important substrates for direct absorption by rice root.
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