Nitrogen dynamics in paddy field under free-air CO_2 enrichment (FACE) examined by the ^<15>N tracer technique   :   開放系高CO_2実験水田圃場における重窒素標識法による窒素の動態解析 

作成者 Hoque, Md. Mozammel, Inubushi, Kazuyuki, Yabashi, Shingo
作成者 (ヨミ) ホック, モハメッド モザンメル, ヤバシ, シンゴ
作成者の別表記 犬伏, 和之, 矢橋, 晨吾
日本十進分類法 (NDC) 613
内容 大気中のCO_2濃度が上昇し続けており, 地球規模での気候の変動が引き起こされ食料生産や自然生態系に大規模な影響を及ぼすと危惧されている.大気CO_2増加が植物生育に及ぼす影響についてはチャンバーを用いた実験が1960年代から行われているが, チャンバー自体の影響(チャンバー効果)を無視できないため, チャンバー効果のない実際の開放系でCO_2濃度を高めるための実験方法FACE(Free-Air-CO_2-Enrichment, 開放系高CO_2実験系)が開発された.本研究は, CO_2濃度を水稲生育期間中, 外気よりも200ppmv増とした水田圃場で生態系にどのような変化が生じるかを明らかにすることを目的として岩手県雫石で実施されたRice FACE実験の一環として, 土壌中の窒素動態に及ぼす影響を重窒素標識法を用いて解析した.水稲移植時に1株分の作土を含む小区画を枠で囲み, 移植時あるいは水稲生育中3回, 基肥以外に^<15>N標識硫安を枠内に均一に施用した.施肥直後または26-35日後に枠内の水稲と土壌(表層0-1cmおよび次表層1-13cm)を採取し, 水稲吸収窒素, 土壌微生物バイオマス窒素, 土壌中アンモニア態窒素およびそれらの重窒素濃度を定量した.水稲生育初期には対照区(大気CO_2濃度)に比べてFACE区で水稲吸収窒素量および施肥由来中窒素量が高かった.水稲吸収窒素に占める施肥窒素由来の割合は水稲生育と共に増加し登熟期にはFACE区で58.06%, 対照区で61.20%となった.微生物バイオマス窒素とアンモニア態窒素は生育期間を通して表層土壌で次表層より多かった.収穫期には高CO_2濃度が表層土壌のバイオマス窒素を対照区に比べ有意に増加させていた.一方, 微生物バイオマス窒素とアンモニア態窒素の施肥由来回収率は, 生育期間を通して表層より次表層で
As part of the FACE (free-air CO_2 enrichment) experiment in a rice paddy field in Shizukuishi (Iwate Prefecture, Japan), a microplot study was conducted to determine the effects of elevated CO_2 on N dynamics. Rice plants were grown under ambient CO_2 (A_<CO2>) or ambient+200ppmv CO_2 (E_<CO2>) conditions throughout the growing season in an Andosol soil. On transplanting day, rice hills with standard growth were selected randomly and enclosed with plow layer soil by stainless steel frames (30.0×17.5×18.0cm; L×B×W) designated as microplots. ^<15>N fertilizer was applied in the microplots uniformly at three different growth stages of rice. Plant and soil (0-1cm upper and ca. 1-13cm lower soil depths) samplings were done destructively 4 different growth stages of rice during the growing season and analyzed for plant N and ^<15>N content, soil microbial biomass N and ^<15>N (B_N and B_<15N>) in addition to soil NH^+_4-N and ^<15>NH^+_4-N. Compared to A_<CO2>, E_<CO2> significantly increased total plant N and ^<15>N (from fertilizer) uptake in the vegetative stage of rice plants. In addition to this, the significant increase of ^<15>N uptake by rice plants was also observed at ripening under E_<CO2>. The percentage of fertilizer ^<15>N in the rice plants increased with the plant growth and it was 58.06 and 61.20-0x1.fa74p+0t harvest under E_<CO2> and A_<CO2>, respectively. Soil microbial biomass N was higher in the upper soil layer than the lower soil layers throughout the growing season. Elevated CO_2 significantly increased microbial biomass N (B_N) in the upper soil layer at harvest compared to A_<CO2>. On the other hand, B_<15N> and ^<15>NH^+_4-N recoveries were consistently higher in the lower soil layer than the upper soil layer throughout the growing season because the fertilizer was applied in the lower soil layer. These results indicate that elevated CO_2 had positive influence with time and space on N dynamics in a paddy field.

公開者 千葉大学園芸学部
コンテンツの種類 紀要論文 Departmental Bulletin Paper
DCMI資源タイプ text
ファイル形式 application/pdf
ISSN 0069-3227
NCID AN00142658
掲載誌情報 千葉大学園芸学部学術報告 Vol.56 page.65-75 (20020329)
情報源 The technical bulletin of Faculty of Horticulture, Chiba University
言語 英語
著者版フラグ publisher

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