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Last Updated :2024/11/19

研究者情報

マスター

アカウント（マスター）

  • 氏名

    当真　要(トウマ　ヨウ), トウマ　ヨウ

所属（マスター）

  • 農学研究院　基盤研究部門　生物機能化学分野

所属（マスター）

  • 農学研究院　基盤研究部門　生物機能化学分野

独自項目

syllabus

  • 2021, 地域環境学特論Ⅰ, Advanced Regional Environment I, 修士課程, 農学院, 水土資源利用・保全、大気の循環、エネルギー収支、物質循環、農業生態系
  • 2021, 温暖化影響学総論, Mitigation of Global Warming Effect, 修士課程, 農学院, 炭素循環、窒素循環、陸域生態系、森林、農地、湿地、泥炭地、永久凍土、土壌、植物、微生物、大気、二酸化炭素、亜酸化窒素、メタン、オゾン、施肥、収穫、耕うん、焼畑、植林、再植林、森林改変、森林火災、環境撹乱、熱帯、温帯、北方、水循環、水資源、バイオマスエネルギー、バイオマス製品、環境ガバナンス
  • 2021, 環境化学, Environmental Chemistry, 学士課程, 農学部, 大気・河川・湖沼・海洋・地下水・土壌の汚染、人工公害物質、ミスト、バイオレメディエーション、バイオマス廃棄物の資源化・循環、ＬＣＡ、植物ストレス
  • 2021, 物理化学, Physical Chemistry, 学士課程, 農学部, 量子論、熱力学第一法則，エントロピー，熱力学第二法則，化学ポテンシャル，化学平衡、膜輸送、分析化学
  • 2021, 土壌及び植物栄養学概論, Introduction of Soil Science and Plant Nutrition, 学士課程, 農学部, 土壌、物質循環、植物生産、環境保全、施肥、栄養生理、栄養生態、不良土壌、根圏、植物－微生物共生
  • 2021, 一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), Freshman Seminar, 学士課程, 全学教育, 食料、安全、作物生産、放射能汚染、食品微生物、酵素利用技術、毒物、ガン、アレルギー、メタボリックシンドローム、腸内細菌叢、保健機能食品
  • 2021, 土壌学Ⅰ, Soil Science I, 学士課程, 農学部, 土壌の概念、生成、風化、粘土鉱物、腐植、酸化還元反応、構造、開放系、物質循環、土壌劣化、砂漠化、酸性化、塩類化、アルカリ化、侵食、踏圧、土壌生産力、土壌診断、施肥、環境保全、富栄養化、地球温暖化、環境保全型農業
  • 2021, 地学概論, Introduction to Geology, 学士課程, 農学部, 地学、地球化学、気象、岩石、鉱物、土壌、水、災害、物質循環

researchmap

プロフィール情報

所属

  • 北海道大学大学院, 農学研究院, 教授

学位

  • 博士(農学)（2008年03月 北海道大学）

プロフィール情報

  • 姓

    当真, トウマ

  • 名

    要, ヨウ

  • ID各種

    201601002711072132

対象リソース

所属

  • 北海道大学大学院, 農学研究院, 教授

業績リスト

研究キーワード

  • 土壌炭素貯留   物質循環   農業生態系   ススキ半自然草地   Biochar   亜酸化窒素   メタン動態   

研究分野

  • ライフサイエンス / 植物栄養学、土壌学
  • 環境・農学 / 環境負荷低減技術、保全修復技術

経歴

  • 2021年04月 - 現在 北海道大学 大学院農学研究院 教授
  • 2016年04月 - 2021年03月 愛媛大学 大学院農学研究科 准教授
  • 2011年07月 - 2016年03月 愛媛大学 農学部 助教
  • 2011年03月 - 2011年06月 北海道大学北方生物圏フィールド科学センター 生物生産研究農場 研究員
  • 2008年04月 - 2011年02月 北海道大学北方生物圏フィールド科学センター 生物生産研究農場 博士研究員

学歴

  • 2005年04月 - 2008年03月   北海道大学大学院   農学研究科   環境資源学専攻地域環境学講座博士後期課程
  • 2003年04月 - 2005年03月   北海道大学大学院   農学研究科   環境資源学専攻地域環境学講座修士課程
  • 1999年04月 - 2003年03月   北海道大学   農学部   生物機能科学科

委員歴

  • 2024年 - 現在   日本学術会議   農学委員会・食料科学委員会合同IUSS分科会連携会員（特任）
  • 2021年04月 - 現在   日本土壌肥料学会   渉外担当理事（国際）
  • 2019年09月 - 現在   木質炭化学会   運営委員
  • 2020年04月 - 2021年03月   日本土壌肥料学会   渉外担当理事補佐

受賞

  • 2023年09月 第21回日本炭化学会研究発表会 日本炭化学会 優秀発表賞 奨励部門
     北海道の小麦畑における籾殻炭の施用がGHG排出に与える影響 
    受賞者: 溝手桃花、喜島仰汰、Ezeaku Victor Ikemefuna、当真要
  • 2023年09月 日本土壌肥料学会2023年度愛媛大会 若手口頭発表優秀賞
     中耕除草による田面水と土壌の攪乱は拡散経路のCH4とN2Oに影響を与えていた 
    受賞者: 浪江日和、島田かさね、当真要、石黒宗秀、波多野隆介
  • 2022年10月 2022年度土壌物理学会大会 第20回（2022年度）優秀ポスター賞
     中耕除草による土壌撹乱の頻度が気泡・拡散経路で排出されるメタンおよび亜酸化窒素に与える影響 
    受賞者: 浪江日和;島田かさね;趙双双;当真要;石黒宗秀;波多野隆介
  • 2022年09月 日本土壌肥料学会2022年度東京大会 若手口頭発表優秀賞
     凍土中の透水プロセスが小雪寒冷地域の流域水循環に与える影響 
    受賞者: 三原州人;倉持寛太;当真要;波多野隆介
  • 2022年09月 日本土壌肥料学会2022年度東京大会 若手ポスター発表優秀賞
     有効土層を考慮した土壌質指標によるバレイショ圃場生産性評価 
    受賞者: 吉村元博;前塚研二;小川ひかり;当真要
  • 2022年09月 日本土壌肥料学会2022年度東京大会 若手ポスター発表優秀賞
     無肥料無農薬水田における多数回中耕除草が温室効果ガス排出に与える影響 －連続した2年間の結果－ 
    受賞者: 島田かさね;浪江日和;趙双双;当真要;石黒宗秀;波多野隆介
  • 2022年09月 日本土壌肥料学会2022年度東京大会 若手ポスター発表優秀賞
     無人航空機空撮画像と物体認識深層学習モデルによる放牧地の糞検出と分布認識 
    受賞者: 安黒守敬;森昭憲;金子真;秋山雄希;上野秀人;倉持寛太;波多野隆介;当真要
  • 2021年09月 日本土壌物理学会 第19回優秀ポスター賞
     水田における気泡メタンフラックス測定装置の開発 
    受賞者: 浪江日和・島田かさね・趙双双・当真要・石黒宗秀・波多野隆介
  • 2021年09月 日本土壌肥料学会北海道大会 若手ポスター発表優秀賞
     無肥料無農薬水田における多数回中耕除草が温室効果ガス排出に与える影響 
    受賞者: 島田かさね;浪江日和;趙双双;当真要;石黒宗秀;波多野隆介
  • 2021年09月 日本土壌肥料学会北海道大会 若手ポスター発表優秀賞
     SWATを用いた畑作農業流域における水・土砂流出の空間変動評価：北海道東部常呂川流域における事例研究 
    受賞者: 三原州人;倉持寛太;当真要;波多野隆介
  • 2019年08月 日本土壌肥料学会静岡大会 ポスター賞
     Nitrogen dynamics in winter-wheat field in Ehime, Southwestern Japan 
    受賞者: Rosalina A. Tamele;当真要;上野秀人
  • 2013年04月 日本土壌肥料学会 奨励賞
     畑草地における温室効果ガス発生と土壌炭素蓄積の制御因子に関する研究 
    受賞者: 当真要
  • 2011年08月 日本土壌肥料学会つくば大会 ポスター賞
     阿蘇ススキ半自然草地における炭素蓄積速度の定量的評価 
    受賞者: 当真要;杉山真二;中坊真;波多野隆介
  • 2007年08月 日本土壌肥料学会 ポスター賞
     インドネシア熱帯泥炭農地土壌における施肥窒素および土壌有機物からのN2O発生 
    受賞者: 当真要;高階史章;Untung Darung;倉持寛太;波多野隆介

論文

  • Lulu Zhou, Shilei Peng, Renjun Liao, Kunihito Mihara, Kanta Kuramochi, Yo Toma, Ryusuke Hatano
    International Journal of Climatology 2024年11月13日 [査読有り]
     
    ABSTRACT Climate extreme events are intensifying globally, posing increasing risks across various sectors. Understanding climate extremes' spatiotemporal patterns and responses to climate change is crucial for effective management, especially on a regional scale. This study examines temperature and precipitation extremes, as well as compound dry‐hot events (CDHEs), in the Ishikari River basin (IRB) of Northeastern Japan, an area of significant socioeconomic importance. We focus on spatiotemporal analysis under multiple scenarios of temperature/precipitation extremes and CDHEs based on statistical downscaled datasets from the Coupled Model Intercomparison Project Phase 6. Results indicate that IRB underwent increased trends of extreme hot periods, extreme droughts, and heavy rainfalls during 1985–2014, which are significantly affected by the North Pacific Oscillation and Southern Oscillation Index. Future projections show that warming temperatures and less rainfall shift asymmetrical impacts on temperature and precipitation extremes, expecting increased warm spells and CDHEs but increased wet durations and less heavy rainfalls. Emission scenarios analysis suggests low‐emission scenarios (SSP1‐2.6) could mitigate their exacerbations, especially for CDHEs (decreased by 139%). Moreover, spatial‐pattern analysis reveals regional heterogeneity in temperature and precipitation extremes, with northern mountainous regions more susceptible to thermal extremes and southern plain regions (e.g., Sapporo city) experiencing prolonged drought and CDHEs. This study provides valuable insights into climate risk management and adaptation strategies.
  • War War Mon, Yo Toma, Hideto Ueno
    Soil Systems 8 3 2024年09月 
    Biochar is stable in soil and can have long-term effects on its physicochemical properties. Hence, a pot experiment was conducted with medium-fertility (MF) and low-fertility (LF) soils after 1 year of rice husk biochar and organic fertilizer application to determine biochar’s residual effects on soil chemical properties, grain yield, and greenhouse gas emissions. In previous years, biochar alone (at application rates of 5 and 10 t ha−1) and biochar combined with chicken manure (CHM) or cow manure (at application rate of 5 t ha−1) were applied to the soil. In the present year, the soils were fertilized with only chemical fertilizers. Results indicated that application of 10 t ha−1 biochar combined with 5 t ha−1 CHM (B10:CHM) produced the highest grain yield and total global warming potential (GWPtotal) in both soils. Regarding grain yield, non-significant results were detected for B10:CHM, B5:CHM, and B10. This study revealed that biochar retains nutrients without annual reapplication and has long-term effects. Although biochar application can suppress N2O emissions effectively, the combined application of biochar 10 t ha−1 and organic manure significantly increased CH4 emissions. Overall, B5:CHM can be recommended for rice cultivation since it improves grain yield without increasing GWPtotal.
  • Nobuki Morita, Yo Toma, Hideto Ueno
    Advances in Bamboo Science 8 2024年08月 
    The disposal of bamboo processing residues and spent tea leaves is an environmental concern, but their reuse as compost can be not only reduce the amount of waste, but can also convert the waste products into valuable resources that provide nutrients to crops and improve soil fertility. Combining bamboo, with its high C/N ratio, and tea leaves with high nitrogen content may produce high quality compost, but its effect on composting rate and nutrient content is unclear. This study evaluated the effect that co-composting of bamboo powder and tea leaves has on composting rate and quality. Three compost types were prepared: B100 (600 kg bamboo powder), B40 (240 kg bamboo powder and 360 kg tea leaves), and B20 (120 kg bamboo powder and 480 kg tea leaves), with two replicates each. The mixed materials were allowed to compost in an outdoor compost shed for 98 d. Peak composting temperatures occurred later for B40 and B20 than for B100, suggesting that the microbial activity of the co-composts may have been reduced during the early composting stage. However, the C/N ratio, NH4+/NO3− ratio, chemical oxygen demand (measured in hot water extracts), and juvenile plant growth experiments using komatsuna (Brassica rapa var. perviridis) revealed that the composting rate was higher in B20 than in B40 and B100. Additionally, at the end of the composting period, B20 had a C/N ratio of approximately 10 along with high total nitrogen and NO3−-N content, indicating an improved compost quality for use as a fertilizer.
  • Nobuki Morita, Yo Toma, Hideto Ueno
    Advances in Bamboo Science 8 2024年08月 
    This study clarified the functional characteristics of microorganisms during the co-composting of bamboo powder and tea leaves. Three treatments were established for 14 weeks of composting: B100 (600 kg bamboo powder), B40 (240 kg bamboo powder and 360 kg tea leaves), and B20 (120 kg bamboo powder and 480 kg tea leaves), with two replicates each. The functional characteristics of the microorganisms were analyzed using a BIOLOG EcoPlate for carbon substrate utilization patterns using kinetic parameters, microbial diversity analysis by calculating diversity indices, and microbial community structure analysis via principal component analysis of kinetic parameters. When bamboo powder was composted alone, the microbial diversity was high in the early composting stage because of the utilization of the rich and complicated carbon substrates. However, in the late composting stage, the microbial diversity was low because of the utilization of poor and simple carbon substrates. In contrast, when bamboo powder and tea leaves were combined, carbon substrate utilization and microbial diversity were low during the early composting stage. In the middle and late stages of composting, abundant carbon substrates became available, and microbial diversity increased. Differences in carbon substrate utilization patterns can be separated by microbial community structure analysis, especially at the end of composting. The communities were divided according to the proportions of bamboo powder and tea leaves. In the early stage of co-composting bamboo powder and tea leaves, microbial activity decreased because of the lower compost temperature and higher tea polyphenol content. However, in the middle and late stages, microbial activity may increase owing to the supply of tea-derived soluble sugars and amino acids. The co-composting of bamboo powder and tea leaves may enhance microbial activity, diversity, and carbon substrate utilization during the middle and late composting stages.
  • Shilei Peng, Xianli Xu, Renjun Liao, Binghui He, Kunihito Mihara, Kanta Kuramochi, Yo Toma, Ryusuke Hatano
    Science of The Total Environment 174744 - 174744 2024年07月 [査読有り][通常論文]
  • 愛媛県のハダカムギ圃場におけるもみ殻炭の施用は土壌炭素を増加し地球温暖化を抑制する
    当真要, 溝手桃花, 辻本泰地, 上野秀人
    日本炭化学会誌 2 2 37 - 45 2024年03月31日 [査読有り][通常論文]
  • Kunihito Mihara, Kanta Kuramochi, Yo Toma, Ryusuke Hatano
    Soil Science and Plant Nutrition 1 - 14 2024年03月14日 [査読有り]
  • War War Mon, Yo Toma, Hideto Ueno
    Soil Systems 8 1 32 - 32 2024年03月10日 [査読有り][通常論文]
     
    The application of biochar is considered an alternative amendment strategy for improving soil fertility. In this study, we performed pot experiments using soils of low and medium fertility to assess the effects of different combinations of biochar and organic manure on the chemical properties of paddy rice soils and determined the best combination to improve the grain yield without increasing N2O and CH4 emissions. The applied treatments were without biochar (control), the application of rice husk biochar alone (5 and 10 t ha−1), and biochar combined with chicken or cow manure. The results indicated that for both soils, the application of 5 t ha−1 biochar combined with 5 t ha−1 chicken manure increased grain yield by improving soil total nitrogen and soil NH4+-N without increasing cumulative N2O and CH4 emissions. Multiple regression analysis showed that when combined with biochar, chicken manure significantly contributed to a higher grain yield and was negatively associated with cumulative CH4, N2O emissions, and total GWP. Furthermore, regardless of soil type, combined applications of biochar and cow manure promoted significant increases in soil available P. Our findings indicate that the C/N ratio of organic manure influences CH4 fluxes, and soil type was identified as a factor driving greenhouse gas emissions.
  • Nobuki Morita, Yo Toma, Hideto Ueno
    Waste 2 1 72 - 84 2024年02月01日 
    The disposal of tea leaves discarded in the tea beverage market and clinker from coal-fired power plants has an impact on the environment; however, there are no reported cases of their combination for composting. Therefore, this study evaluated the effect of adding clinker from a coal-fired power plant to compost based on tea leaves, an organic waste product, on the composting rate and quality. The tea leaves-only compost was designated as Clinker 0%, and composts with 20% (w/w), 40% (w/w), and 60% (w/w) tea leaves supplemented with clinker were designated as Clinker 20, 40, and 60%, respectively. Each mixed material was placed in a 35 L polypropylene container with a lid and allowed to compost for 95 days. The composting rate was evaluated by the chemical oxygen demand (COD) in hot water extract and plant tests using juvenile komatsuna (Brassica rapa var. perviridis). The addition of clinker reduced the COD at the beginning of composting by 52.0, 74.3, and 86.7% in Clinker 20, 40, and 60%, respectively, compared to Clinker 0%. Furthermore, root elongation one month after composting was inhibited by Clinker 0% (60.1% relative to distilled water), but not by the addition of clinker (91.7–102.7% relative to distilled water). This suggests that the addition of clinker to tea leaf compost may accelerate composting.
  • Syuntaro Hiradate, Masahiko Katoh, Shuji Sano, Shigeto Sudo, Soh Sugihara, Yo Toma
    Soil Science and Plant Nutrition 70 1 1  2024年
  • Shilei Peng, Kunihito Mihara, Xianli Xu, Kanta Kuramochi, Yo Toma, Ryusuke Hatano
    CATENA 234 107605 - 107605 2024年01月
  • Nobuki Morita, Yo Toma, Yasuhiko Kato, Tooru Izumiya, Hideto Ueno
    Agronomy 13 12 2023年12月 
    The liquid waste (LW) discharged during bioethanol production needs treatment. In this study, LW was applied to corn, and its effects on corn growth, yield, and nitrogen (N) content, as well as on soil chemical properties, were evaluated. Five treatments were applied during corn cultivation: no fertilizer (NF), chemical fertilizer (CF), LW at a standard application rate (LW1.0), LW at 1.7 times the rate of LW1.0 (LW1.7), and split application of LW1.7 (S-LW1.7) in six replications. The amount of N applied was 30 kg 10a−1 for CF and LW1.0, and 51 kg 10a−1 for LW1.7 and S-LW1.7. N was applied separately three times in CF, LW1.0, and LW1.7 and six times in S-LW1.7. A higher corn yield, corn ear weight, and number of leaves was observed in LW treatments than in CF. N content of the corn plant top was higher in S-LW1.7 than in LW1.7; N availability was 56.9% and 40.5% higher, respectively, indicating that split application improved N availability. Soil total N content increased significantly in LW treatments, and soil total carbon content tended to increase in S-LW1.7. Therefore, application of LW could increase corn yield and soil fertility, and its effect could be enhanced by split application.
  • 佐々木 章晴, 鈴木 理恵, 山崎 慶太, 野口 賢次, 佐藤 研一, 当真 要
    環境情報科学論文集 37 52 - 57 2023年12月
  • Kunihito Mihara, Kanta Kuramochi, Yo Toma, Ryusuke Hatano
    Soil Science and Plant Nutrition 1 - 13 2023年10月06日
  • Motohiro Yoshimura, Kenji Maezuka, Yo Toma
    Soil Science and Plant Nutrition 69 5-6 315 - 326 2023年08月05日 [査読有り][通常論文]
  • 安黒守敬, 森昭憲, 金子真, 秋山雄希, 花木紅実, 上野秀人, 倉持寛太, 波多野隆介, 当真要
    日本土壌肥料学雑誌 94 5 315 - 326 2023年07月 [査読有り][通常論文]
  • Shilei Peng, Chunying Wang, Zhan Li, Kunihito Mihara, Kanta Kuramochi, Yo Toma, Ryusuke Hatano
    Scientific Reports 13 1 2023年01月05日 
    AbstractSimulation of future climate changes, especially temperature and rainfall, is critical for water resource management, disaster mitigation, and agricultural development. Based on the category-wise indicator method, two preferred Global Climate Models (GCMs) for the Ishikari River basin (IRB), the socio-economic center of Hokkaido, Japan, were examined from the newly released Coupled Model Intercomparison Project Phase 6 (CMIP6). Climatic variables (maximum/minimum temperature and precipitation) were projected by the Statistical DownScaling Model (SDSM) under all shared socioeconomic pathway-representative concentration pathway (SSP-RCP) scenarios (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0, SSP5-3.4OS, and SSP5-8.5) in two phases: 2040–2069 (2040s) and 2070–2099 (2070s), with the period of 1985–2014 as the baseline. Predictors of SDSM were derived from CMIP6 GCMs and the reanalysis dataset NOAA-CIRES-DOE 20th Century Reanalysis V3 (20CRv3). Results showed that CMIP6 GCMs had a significant correlation with temperature measurements, but could not represent precipitation features in the IRB. The constructed SDSM could capture the characteristics of temperature and precipitation during the calibration (1985–1999) and validation (2000–2014) phases, respectively. The selected GCMs (MIROC6 and MRI-ESM-2.0) generated higher temperature and less rainfall in the forthcoming phases. The SSP-RCP scenarios had an apparent influence on temperature and precipitation. High-emission scenarios (i.e., SSP5-8.5) would project a higher temperature and lower rainfall than the low-emission scenarios (e.g., SSP1-1.9). Spatial–temporal analysis indicated that the northern part of the IRB is more likely to become warmer with heavier precipitation than the southern part in the future. Higher temperature and lower rainfall were projected throughout the late twenty-first century (2070s) than the mid-century (2040s) in the IRB. The findings of this study could be further used to predict the hydrological cycle and assess the ecosystem's sustainability.
  • David S. Howlett, J. Ryan Stewart, Jun Inoue, Masanori Saito, DoKyoung Lee, Hong Wang, Toshihiko Yamada, Aya Nishiwaki, Fabián G. Fernández, Yo Toma
    Agriculture 12 1 88 - 88 2022年01月10日 [査読有り][通常論文]
     
    Miscanthus-dominated semi-natural grasslands in Japan appear to store considerable amounts of soil C. To estimate the long-term effect of Miscanthus vegetation on the accumulation of soil carbon by soil biota degradation in its native range, we measured total soil C from the surface to a 1.2 m depth along a catena toposequence in three annually burned grasslands in Japan: Kawatabi, Soni, and Aso. Soil C stock was estimated using a radiocarbon age and depth model, resulting in a net soil C accumulation rate in the soil. C4-plant contribution to soil C accumulation was further estimated by δ13C of soil C. The range of total soil C varied among the sites (i.e., Kawatabi: 379–638 Mg, Soni: 249–484, and Aso: 372–408 Mg C ha−1). Catena position was a significant factor at Kawatabi and Soni, where the toe slope soil C accumulation exceeded that of the summit. The soil C accumulation rate of the whole horizon in the grasslands, derived C mainly from C4 plant species, was 0.05 ± 0.02 (Average ± SE), 0.04 ± 0.00, and 0.24 ± 0.04 Mg C ha−1 yr−1 in Kawatabi, Soni, and Aso, respectively. Potential exists for long-term sequestration of C under M. sinensis, but the difference in the C accumulation rate can be influenced by the catena position and the amount of vegetation.
  • Auldry Chaddy, Lulie Melling, Kiwamu Ishikura, Kah Joo Goh, Yo Toma, Ryusuke Hatano
    Atmosphere 12 10 1340 - 1340 2021年10月13日 [査読有り][通常論文]
     
    A long-term study on the effect of nitrogen (N) fertilization on soil carbon dioxide (CO2) fluxes in tropical peatland was conducted to (1) quantify the annual CO2 emissions from an oil palm plantation under different N application rates and (2) evaluate the temporal effects of groundwater level (GWL) and water-filled pore space (WFPS) on soil organic carbon (SOC) and CO2 fluxes. Monthly measurement of soil CO2 fluxes using a closed chamber method was carried out from January 2010 until December 2013 and from January 2016 to December 2017 in an oil palm plantation on tropical peat in Sarawak, Malaysia. Besides the control (T1, without N fertilization), there were three N treatments: low N (T2, 31.1 kg N ha−1 year−1), moderate N (T3, 62.2 kg N ha−1 year−1), and high N (T4, 124.3 kg N ha−1 year−1). The annual CO2 emissions ranged from 7.7 ± 1.2 (mean ± SE) to 16.6 ± 1.0 t C ha−1 year−1, 9.8 ± 0.5 to 14.8 ± 1.4 t C ha−1 year−1, 10.5 ± 1.8 to 16.8 ± 0.6 t C ha−1 year−1, and 10.4 ± 1.8 to 17.1 ± 3.9 t C ha−1 year−1 for T1, T2, T3, and T4, respectively. Application of N fertilizer had no significant effect on annual cumulative CO2 emissions in each year (p = 0.448), which was probably due to the formation of large quantities of inorganic N when GWL was temporarily lowered from January 2010 to June 2010 (−80.9 to −103.4 cm below the peat surface), and partly due to low soil organic matter (SOM) quality. A negative relationship between GWL and CO2 fluxes (p < 0.05) and a positive relationship between GWL and WFPS (p < 0.001) were found only when the oil palm was young (2010 and 2011) (p < 0.05), indicating that lowering of GWL increased CO2 fluxes and decreased WFPS when the oil palm was young. This was possibly due to the fact that parameters such as root activity might be more predominant than GWL in governing soil respiration in older oil palm plantations when GWL was maintained near or within the rooting zone (0–50 cm). This study highlights the importance of roots and WFPS over GWL in governing soil respiration in older oil palm plantations. A proper understanding of the interaction between the direct or indirect effect of root activity on CO2 fluxes and balancing its roles in nutrient and water management strategies is critical for sustainable use of tropical peatland.
  • 岩崎真也, 遠藤, 波多野隆介, 当真要
    Soil Science and Plant Nutrition 67 5 1 - 12 2021年08月11日
  • Muhammad Iqbal Fauzan, Syaiful Anwar, Budi Nugroho, Hideto Ueno, Yo Toma
    Agriculture 11 7 661 - 661 2021年07月13日 [査読有り][通常論文]
     
    Organic matter, fertilizers, and soil amendments are essential for sustainable agricultural practices to guarantee soil productivity. However, these materials can increase the emission of greenhouse gases (GHGs) such as CH4 and N2O. Thus, technologies for reducing GHG emissions in concert with the increase in rice production from rice fields are needed. The objectives of this study were to determine the best chicken manure (CM) and steel slag (SS) combination to mitigate CH4, N2O, and CO2 emissions in an incubation experiment, to identify the best CM:SS ameliorant mixture to mitigate CH4 and N2O, and to evaluate dry biomass and grain yield in a pot experiment. A randomized block design was established with four treatments, namely conventional (chemical fertilizer only) and three combinations of different ratios of CM and SS (1:1, 1:1.5, and 1:2.5), with five replications in a pot experiment. CM:SS (1:2.5) was identified as the best treatment for mitigating CH4, N2O, and CO2 in the incubation experiment. However, CM:SS (1:1.5) was the best CM and SS ameliorant for mitigating CH4 and N2O in the pot experiment. The global warming potential of CH4 and N2O revealed that CM:SS (1:1.5) had the lowest value. None of the combinations of CM and SS significantly increased dry biomass and grain yield.
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  • 当真要, 武知佑樹, 井上文乃, 中矢夏子, 細谷和宏, 山下陽一, 阿立真崇, 河野貴幸, 上野秀人
    Soil Science and Plant Nutrition 2021年05月 [査読有り][通常論文]
  • 中山 典子, 当真 要, 古谷 浩志, 波多野 隆介, 豊田 岐聡
    日本土壌肥料学会講演要旨集 66 9 - 9 一般社団法人 日本土壌肥料学会 2020年09月01日
  • タメレ ロザリナ アルマンド, 当真 要, 上野 秀人
    Soil Science and Plant Nutrition 2020年08月 [査読有り][通常論文]
     
    窒素（N）は作物生産に最も重要な制限因子である．従って，その循環の解明はN利用効率を向上させ溶脱や亜酸化窒素（N2O）排出等の環境負荷の低減に重要である．2017年11月12日から2018年6月3日および2018年11月12日から2019年5月27日にかけて，愛媛県の冬小麦畑のN動態を2年間調査した．また，N動態モデルを設け慣行施肥（被覆肥料を含む120 N kg ha-1）栽培でのN収支を求めた．さらに，植物の肥料Nの吸収量と施肥N由来のN2O発生量を求めるため2処理区（無N区と低N区）を加え，計3処理区を4反復で設けた．土壌からのN2O発生はクローズドチャンバー法を用い，間接排出は排出係数を用いて推定した．N溶脱量と土壌無機化N量はマイクロライシメーター，大気N沈着量はレイントラップで測定した．小麦のN吸収量（208 kg N ha-1）と収穫N量（190 kg N ha-1）は主要なNアウトプットだった．小麦が吸収したNの58.1％が施肥N由来，41.9％が土壌由来だった．また，深さ30 cmまでの表層土壌からのN溶脱量（30.1 kg N ha-1）も主要なNアウトプットであった。表層土壌の無機化N量は104 kg N ha-1と見積もられ，溶脱N量の91%を占めていた．N2O排出量は直接・間接放出共に少なかった．2年間の平均N収支は-86.8 kg N ha-1と圃場からNが減少しており，土壌のN状態を維持し環境にやさしい農業の実施には，Nの溶出を抑制できる堆肥やバイオ炭等の有機物で土壌Nを補う必要がある．
  • Rosalina Armando Tamele, Hideto Ueno, Yo Toma, Nobuki Morita
    Agriculture 10 7 272 - 272 2020年07月05日 [査読有り][通常論文]
     
    The rising cost of inorganic fertilizers, coupled with their adverse effects on soil conditions, has resulted in increasing interest in organic amendments. The objective of the present study was to evaluate the effect of organic amendments (OAs) with different C/N ratios on nitrogen use efficiency (NUE) and recovery rate, as well as on the growth and yield of Zea mays and soil properties. A precise pot experiment was conducted on a low-fertile, sandy-loam soil, and the dynamics of nitrogen (N) were also analyzed by the A-value method, using 15N tracer. The plant height of the treatment groups decreased in the following order: inorganic fertilizer (IF) = rapeseed waste (RW) > chicken manure (CnM) > bamboo tealeaf (BTL) > cow manure (CwM) > bamboo compost (BC). Furthermore, the maize fertilized with RW only took up half of the N in IF, despite producing the same yield, which indicates that the physiological nitrogen efficiency (PUE) of RW was twice as high as that of IF. RW and CnM were regarded as valuable fertilizers that could be used to replace inorganic fertilizers. A linear relationship between the N mineralization of the OAs was obtained by an incubation test and the pot experiments, estimating the effect of OA application on the maize. Maize plants mainly absorbed N derived from fertilizers; however, for the both sources of N (fertilizer and soil), N was mainly accumulated in grains followed by the leaves, stem, and root, suggesting that studies should be conducted to improve soil N use efficiency.
  • Noriko Nakayama, Yo Toma, Yusuke Iwai, Hiroshi Furutani, Toshinobu Hondo, Ryusuke Hatano, Michisato Toyota
    Atmospheric Measurement Techniques 13 12 6657 - 6673 2020年03月 [査読有り][通常論文]
     
    We developed a mass spectrometric soil-gas flux measurement system using a portable high-resolution multiturn time-of-flight mass spectrometer, called MULTUM, and we combined it with an automated soil-gas flux chamber for the continuous field measurement of multiple gas concentrations with a high temporal resolution. The developed system continuously measures the concentrations of four different atmospheric gases (NO2, CH4, CO2, and field soil- atmosphere flux measurements of greenhouse gases (NO2, O2) ranging over 6 orders of magnitude at one time using a single gas sample. The measurements are performed every 2.5 min with an analytical precision (2 standard deviations) of34 ppbv for NO2;170 ppbv, CH4; 16 ppmv, CO2; and 0:60 vol %, O2 at their atmospheric concentrations. The developed system was used for the continuous field soil-atmosphere flux measurements of greenhouse gases (NO2, CH4, and CO2) and O2 with a 1 h resolution. The minimum quantitative fluxes (2 standard deviations) were estimated via a simulation as 70.2 μgNm-2 h-1 for NO2; 139 μgCm-2 h-1, CH4; 11.7 mg Cm-2 h-1, CO2; and 9.8 gO2 m-2 h-1, O2. The estimated minimum detectable fluxes (2 standard deviations) were 17.2 μgNm-2 h-1 for NO2; 35.4 μgCm-2 h-1, CH4; 2.6 mg Cm-2 h-1, CO2; and 2.9 gO2 m-2 h-1, O2. The developed system was deployed at the university farm of the Ehime University (Matsuyama, Ehime, Japan) for a field observation over 5 d. An abrupt increase in NO2 flux from 70 to 682 μgNm-2 h-1 was observed a few hours after the first rainfall, whereas no obvious increase was observed in CO2 flux. No abrupt NO2 flux change was observed in succeeding rainfall events, and the observed temporal responses at the first rainfall were different from those observed in a laboratory experiment. The observed differences in temporal flux variation for each gas component show that gas production processes and their responses for each gas component in the soil are different. The results of this study indicate that continuous multiple gas concentration and flux measurements can be employed as a powerful tool for tracking and understanding underlying biological and physicochemical processes in the soil by measuring more tracer gases such as volatile organic carbon, re- active nitrogen, and noble gases, and by exploiting the broad versatility of mass spectrometry in detecting a broad range of gas species.
  • 黒ボク土,ジャーガル,マサ土におけるNaClの化学的挙動が電気伝導度とトマト生育に与える影響
    富井春幸, 上野秀人, 当真 要
    農作業研究 55 1 13 - 22 2020年03月 [査読有り][通常論文]
  • マサ土の塩類集積時における電気伝導度測定法とトマト生育との関係
    富井春幸, 上野秀人, 当真 要
    農作業研究 55 1 3 - 11 2020年03月 [査読有り][通常論文]
  • Effect of bamboo biochar application on rice growth and yield and a regional cycle model of bamboo materials in hilly and mountainours area in Japan
    Yo Toma, Wataru Fujitani, Takemichi Tsurumi, Keiko Tsurumi, Hideto Ueno
    木質炭化学会誌 16 2 49 - 59 2020年03月 [査読有り][通常論文]
  • レンコン浅床栽培におけるボール田面への浮揚がハス生育とレンコン収量に与える効果
    溝渕佐織, 当真要, 上野秀人
    農作業研究 54 3 143 - 149 2019年08月 [査読有り][通常論文]
     
    本研究では，レンコン浅床栽培における田面へのボール浮揚がハスの生育や肥大根茎（レンコン）の収量に与える影響を評価した．直径80 mmのポリエステル製白色ボールを田面に浮かべ，2018年4月から9月にかけてハスを栽培した．ボール浮揚により，ボールの保温効果と田面水の蒸発量抑制による顕熱の増加に起因して地温上昇が生じ，ハスの生育が促進された．さらに，地温上昇は地下茎の分岐を促進したと推測され，肥大根茎の数の増加により収量が増加していた．ボールによる田面の遮蔽は，ハス生育促進だけでなく灌漑水の節水効果も期待できることが明らかになった．開花後の立葉（抽水葉）の葉色値上昇が肥大根茎の重量を増加していたことから，ボール浮揚に加え開花終了後の窒素肥料の追肥により，より大きな肥大根茎の数を増やすことができる可能性がある．
  • Yo Toma, Nukhak Nufita Sari, Koh Akamatsu, shingo Oomori, Osamu Nagata, Seiichi Nishimura, Benito H. Purwanto, Hideto Ueno
    Agriculture 9 2 29  2019年02月 [査読有り][通常論文]
     
    Green manure application helps maintain soil fertility, reduce chemical fertilizer use, and carbon sequestration in the soil. Nevertheless, the application of organic matter in paddy fields induces CH4 and N2O emissions. Prolonging mid-season drainage reduces CH4 emissions in paddy fields. Therefore, the combined effects of green manure application and mid-season drainage prolongation on net greenhouse gas emission (NGHGE) were investigated. Four experimental treatments were set up over a 2-year period: conventional mid-season drainage with (CMG) and without (CM) green manure and prolonged (4 or 7 days) mid-season drainage with (PMG) and without (PM) green manure. Astragalus sinicus L. seeds were sown in autumn and incorporated before rice cultivation. No significant difference in annual CH4 and N2O emissions, heterotrophic respiration, and NGHGE between treatments were observed, indicating that green manure application and mid-season drainage prolongation did not influence NGHGE. CH4 flux decreased drastically in PM and PMG during mid-season drainage under the hot and dry weather conditions. However, increasing applied carbon increases NGHGE because of increased CH4 and Rh. Consequently, combination practice of mid-season drainage prolongation and green manure utilization can be acceptable without changing NGHGE while maintaining grain yield in rice paddy fields under organically managed rice paddy fields.
  • 当真要, 大西 まゆ, 白鳥 豊, 須藤 重人, 西村 誠一, 上野 秀人
    日本土壌肥料学雑誌 89 4 302 - 310 2018年08月 [査読有り][通常論文]
     
    ブロッコリーの秋作において，被覆尿素または被覆硝カルの施用が土壌からのN2O発生に与える影響について調べた．2016年9月から11月にかけて，愛媛大学農学部附属農場に無施肥（C）区，尿素（U）区，被覆尿素（CU）区，および被覆硝カル（CN）区をそれぞれ4反復で設けた．CU区とCN区ではU区より全窒素（N）施用量を2割減らし，施用Nの4割を被覆Nで施用した．N2Oフラックスを測定し，施用Nから発生したN2Oの割合（EF）を算出した．さらに，地温，土壌pH，土壌アンモニウム態Nおよび硝酸態N含量を測定し，作土層からの無機N溶脱量と頂花蕾収量，N吸収量およびN利用率を求めた．被覆尿素や被覆硝カルのEFはそれぞれ0.62％および0.23％で尿素（0.06％）よりも高い傾向にあり，被覆尿素および被覆硝カルの施用は尿素を分施するブロッコリー秋作体系においてN2O発生量を削減する効果は見られなかった．その原因として，生育前半の高温と多雨が被覆肥料Nの溶出とその後の硝化・脱窒におけるN2O生成を促進し，かつ生育後半に追肥で施用した尿素Nは低温と少雨のためN2O生成が少なかったためと考えられた．CN区では収量もC区と同程度に低く無機N溶脱量は最も多く，生育前半の多雨によるN溶脱が収量にも影響した可能性がある．以上より，尿素に代えて被覆尿素を用いる場合，肥料施用時期の気象条件によってはN2O発生量が増加する可能性があり，また被覆硝カルは収量低下や肥料N溶脱が増加することが懸念された．
  • 中山 典子, 当真 要, 波多野 隆介, 豊田 岐聡
    日本地球化学会年会要旨集 65 99  一般社団法人日本地球化学会 2018年 
    土壌から排出されるN2O・CH4・CO2は、土壌中の多種多様な微生物によって生成・消費されるため、これらのガス種の同時フラックス測定を行うことができれば、温室効果ガスの排出量推定だけでなく、土壌中の生物群構造やそれらの生物活性状態の評価も可能となる。本発表では、多成分ガス測定MULTUMシステムと土壌ガスチャンバー法とを組み合わせた連続フラックス測定システムを用いて、土壌試料を用いたO2, CO2, CH4, N2O濃度を2分間隔で連続測定し、①地温や土壌水分率などの環境変化が、土壌起源ガスの大気との交換に与える影響を定量的に評価、②得られた情報から土壌中の生物活性状態の変化を考察した結果を報告する。
  • Yo Toma, Takeshi Higuchi, Osamu Nagata, Yasuhiko Kato, Tooru Izumiya, Shingo Oomori, Hideto Ueno
    Agriculture (Switzerland) 7 2 1 - 11 2017年02月08日 [査読有り][通常論文]
     
    Nitrous oxide (N2O) emissions from agricultural fields are an important source of the increasing atmospheric N2O concentration. We conducted a two-year investigation of soil N2O emissions induced by the application of combined organic and synthetic fertilizer (COS) and distilled silage waste (DSW). Three experimental treatments were applied to a Citrus unshiu field in January 2013 in Ehime, Japan: no fertilizer (NF), COS, and DSW. The applied nitrogen (N) from DSW was 192 and 244 kg N ha-1 in the first and second years, respectively, although the N application in COS was 192 kg N ha-1 in both years. The main N forms in COS and DSW were ammonium- and nitrate-N, respectively. Soil N2O and carbon dioxide fluxes, soil chemical properties, and mineral N leaching from topsoil were measured. The soil N2O flux increased after fertilization in COS and DSW, and a higher N2O efflux after supplemental fertilization was induced by warm and wet soil conditions. The emission factor of N2O was higher in COS (2.02%) than in DSW (1.18%), while N leaching was higher in DSW than in COS. The organic materials remaining after the application possibly increased the N2O emissions in the summer season. Therefore, to mitigate N2O emissions in citrus orchards, fertilizer containing organic materials should be applied during a cool and dry season.
  • Kiwamu Ishikura, Hiroyuki Yamada, Yo Toma, Fumiaki Takakai, Tomoaki Morishita, Untung Darung, Atfritedy Limin, Suwido H. Limin, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 63 1 1 - 13 2017年 [査読無し][通常論文]
     
    Soil respiration (SR) rate was measured at the burned land (BL), the cropland (CL), the forest land (FL) and the grassland (GL) of a tropical peatland in Central Kalimantan, Indonesia from 2002 to 2011 for the purpose of analysis with a relation to the drying and rewetting. The SR rate was fitted with groundwater level (GWL) to the equation of log(SR) = alpha -beta x GWL using hierarchical Bayesian analysis where alpha and beta were regression coefficients classified by GWL changing directions (drying, rewetting and fluctuating), water-filled pore space (WFPS) ranges in topsoil (low 0-0.54, intermediate 0.54-0.75 and high 0.75-1 m(3) m(-3)), and land uses (BL, CL, FL and GL). SR rate (Mean +/- SD, mg C m(-2) h(-1)) was the significantly largest in the CL (333 +/- 178) followed by GL (259 +/- 151), FL (127 +/- 69) and lastly BL (100 +/- 90). In the CL, the significantly larger SR rate was found in the rewetting period than in the drying period in the high WFPS range. Also, the significantly steeper slope (beta) in the rewetting period was obtained in the high WFPS range than in the drying period. These results suggested that the rewetting of peatland enhanced the SR rate rapidly in the CL, and that the further rise of GWL decreased the SR rate. In contrast, the SR rate in the rewetting period was significantly smaller than in the drying period in the BL in the high WFPS range, because the BL in the high WFPS range was flooded in most cases. The SR rate in the rewetting period was not significantly different from the drying period in the FL and GL. All of beta were significant in the high WFPS range in all land uses, but not in the low-intermediate WFPS ranges, suggesting that GWL was not controlling factor of the SR rate when the GWL was deep due to the disconnection of capillary force under dry conditions. According to the results of correlation analysis of the alpha and beta, the a was significantly correlated with relative humidity, soil temperature and soil pH, suggesting that the a was enhanced by dry condition, high soil temperature and neutralization of soil acidity, respectively. The beta was significantly correlated with exchangeable Na+ and Mg2+ in the soil, but the reason was not clear. In conclusion, SR rate was enhanced by rising GWL with rewetting in the CL in the high WFPS ranges as well as by deepening GWL.
  • Xi Li, Yo Toma, Jagadeesh Yeluripati, Shinya Iwasaki, Sonoko D. Bellingrath-Kimura, Edward O. Jones, Ryusuke Hatano
    SCIENCE OF THE TOTAL ENVIRONMENT 554 293 - 302 2016年06月 [査読無し][通常論文]
     
    Soil C sequestration in croplands is deemed to be one of the most promising greenhouse gas mitigation options for agriculture. We have used crop-level yields, modeled heterotrophic respiration (Rh) and land use data to estimate spatio-temporal changes in regional scale net primary productivity (NPP), plant C inputs, and net biome productivity (NBP) in northern Japan's arable croplands and grasslands for the period of 1959-2011. We compared the changes in C stocks derived from estimated NBP and using repeated inventory datasets for each individual land use type from 2005 to 2011. For the entire study region of 2193 ha, overall annual plant C inputs to the soil constituted 37% of total region NPP. Plant C inputs in upland areas (excluding bush/fallow) could be predicted by climate variables. Overall NBP for all land use types increased from -1.26 Mg C ha(-1) yr(-1) in 1959-0.26 Mg C ha(-1) yr(-1) in 2011. However, upland and paddy fields showed a decreased in NBP over the period of 1959-2011, under the current C input scenario. From 1988, an increase in agricultural abandonment (bush/fallow) and grassland cover caused a slow increase in the regional C pools. The comparison of carbon budgets using the NBP estimation method and the soil inventory method indicated no significant difference between the two methods. Our results showed C loss in upland crops, paddy fields and sites that underwent land use change from paddy field to upland sites. We also show C gain in grassland from 2005 to 2011. An underestimation of NBP or an overestimation of repeated C inventories cannot be excluded, but either method may be suitable for tracking absolute changes in soil C, considering the uncertainty associated with these methods. (C) 2016 Elsevier B.V. All rights reserved.
  • Shingo Oomori, Yo Toma, Osamu Nagata, Hideto Ueno
    SOIL SCIENCE AND PLANT NUTRITION 62 5-6 553 - 560 2016年 [査読有り][通常論文]
     
    Biochar application can reduce global warming via carbon (C) sequestration in soils. However, there are few studies investigating its effects on greenhouse gases in rice (Oryza sativa L.) paddy fields throughout the year. In this study, a year-round field experiment was performed in rice paddy fields to investigate the effects of biochar application on methane (CH4) and nitrous oxide (N2O) emissions and C budget. The study was conducted on three rice paddy fields in Ehime prefecture, Japan, for 2 years. Control (Co) and biochar (B) treatments, in which 2-cm size bamboo biochar (2 Mg ha(-1)) was applied, were set up in the first year. CH4 and N2O emissions and heterotrophic respiration (Rh) were measured using a closed-chamber method. In the fallow season, the mean N2O emission during the experimental period was significantly lower in B (67 g N ha(-1)) than Co (147 g N ha(-1)). However, the mean CH4 emission was slightly higher in B (2.3 kg C ha(-1)) than Co (1.2 kg C ha(-1)) in fallow season. The water-filled pore space increased more during the fallow season in B than Co. In B, soil was reduced more than in Co due to increasing soil moisture, which decreased N2O and increased CH4 emissions in the fallow season. In the rice-growing season, the mean N2O emission tended to be lower in B (-104 g N ha(-1)) than Co (-13 g N ha(-1)), while mean CH4 emission was similar between B (183 kg C ha(-1)) and Co (173 kg C ha(-1)). Due to the C release from applied biochar and soil organic C in the first year, Rh in B was higher than that in Co. The net greenhouse gas emission for 2 years considering biochar C, plant residue C, CH4 and N2O emissions, and Rh was lower in B (5.53 Mg CO(2)eq ha(-1)) than Co (11.1 Mg CO(2)eq ha(-1)). Biochar application worked for C accumulation, increasing plant residue C input, and mitigating N2O emission by improving soil environmental conditions. This suggests that bamboo biochar application in paddy fields could aid in mitigating global warming.
  • Yo Toma, Toshihiko Yamada, Fabian G. Fernandez, Aya Nishiwaki, Ryusuke Hatano, J. Ryan Stewart
    SOIL SCIENCE AND PLANT NUTRITION 62 1 80 - 89 2016年01月 [査読無し][通常論文]
     
    Increasing greenhouse gas emissions from anthropogenic activities continue to be a mounting problem worldwide. In the semi-natural Miscanthus sinensis Andersson; grasslands of Aso, Kumamoto, Japan, which have been managed for thousands of years, we measured soil methane (CH4) and nitrous oxide (N2O) emissions before and after annual controlled burns. We estimated annual soil carbon (C) accumulation, and CH4 and N2O emissions induced by biomass burning in 2009 and 2010, to determine the impacts of this ecosystem and its management on global warming. Environmental factors affecting soil CH4 and N2O fluxes were unknown, with no effect of annual burning observed on short-term soil CH4 and N2O emissions. However, deposition of charcoal during burning may have enhanced CH4 oxidation and N2O consumption at the study site, given that emissions (CH4: -4.33kgCha(-1) yr(-1), N2O: 0.17kgNha(-1) yr(-1)) were relatively lower than those measured in other land-use types. Despite significant emission of CH4 and N2O during yearly burning events in early spring, the M. sinensis semi-natural grassland had a large annual soil C accumulation, which resulted in a global warming potential of -4.86 Mg CO(2)eq ha(-1) yr(-1). Consequently, our results indicate that long-term maintenance of semi-natural M. sinensis grasslands by annual burning can contribute to the mitigation of global warming.
  • Yo Toma, Shingo Oomori, Asuka Maruyama, Hideto Ueno, Osamu Nagata
    SOIL SCIENCE AND PLANT NUTRITION 62 1 69 - 79 2016年01月 [査読無し][通常論文]
     
    Agricultural fields, including rice (Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH4) and nitrous oxide (N2O). Organic matter application, such as straw and organic fertilizer, enhances CH4 emission from paddy fields. In addition, rice straw management after harvest regulates CH4 emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH4 and N2O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH4 and N2O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH4 emission and the emission factor for CH4 (EFCH4) in the rice-growing season, suggesting that the substrate for CH4 production was reduced by autumn and spring tillage in the fallow season. Higher EFCH4 [1.8-2.0kgcarbon (C)ha(-1) d(-1)] was observed when more straw was applied (6.9-7.2Mgha(-1)) in the second year. Organic fertilizer application induced higher CH4 emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EFCH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N2O efflux during the rice-growing season in the second year, but N2O emissions were not affected by winter tillage. Although paddy fields can act as an N2O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N2O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N2O (EFN2O) can be applied, and EFN2O of organic fertilizer should be considered during the estimation of N2O emission in the paddy field.
  • Lindsay V. Clark, J. Ryan Stewart, Aya Nishiwaki, Yo Toma, Jens Bonderup Kjeldsen, Uffe Jorgensen, Hua Zhao, Junhua Peng, Ji Hye Yoo, Kweon Heo, Chang Yeon Yu, Toshihiko Yamada, Erik J. Sacks
    JOURNAL OF EXPERIMENTAL BOTANY 66 14 4213 - 4225 2015年07月 [査読無し][通常論文]
     
    Unilateral introgression from diploids to tetraploids has been hypothesized to be an important evolutionary mechanism in plants. However, few examples have been definitively identified, perhaps because data of sufficient depth and breadth were difficult to obtain before the advent of affordable high-density genotyping. Throughout Japan, tetraploid Miscanthus sacchariflorus and diploid Miscanthus sinensis are common, and occasionally hybridize. In this study, 667 M. sinensis and 78 M. sacchariflorus genotypes from Japan were characterized using 20 704 SNPs and ten plastid micro-satellites. Similarity of SNP genotypes between diploid and tetraploid M. sacchariflorus indicated that the tetraploids originated through autopolyploidy. Structure analysis indicated a gradient of introgression from diploid M. sinensis into tetraploid M. sacchariflorus throughout Japan; most tetraploids had some M. sinensis DNA. Among phenotypically M. sacchariflorus tetraploids, M. sinensis ancestry averaged 7% and ranged from 1-39%, with introgression greatest in southern Japan. Unexpectedly, rare (similar to 1%) diploid M. sinensis individuals from northern Japan were found with 6-27% M. sacchariflorus ancestry. Population structure of M. sinensis in Japan included three groups, and was driven primarily by distance, and secondarily by geographic barriers such as mountains and straits. Miscanthus speciation is a complex and dynamic process. In contrast to limited introgression between diploid M. sacchariflorus and M. sinensis in northern China, selection for adaptation to a moderate maritime climate probably favoured cross-ploidy introgressants in southern Japan. These results will help guide the selection of Miscanthus accessions for the breeding of biomass cultivars.
  • Kossonou G. Anzoua, Kenji Suzuki, Shinichi Fujita, Yo Toma, Toshihiko Yamada
    GRASSLAND SCIENCE 61 2 83 - 91 2015年06月 [査読無し][通常論文]
     
    Miscanthus xgiganteus has potential as a biomass feedstock for bioenergy production in cold environments. However, its sterility, high cost propagation and relative lack of cold tolerance constrain its cultivation especially during its first winter. Diploid Miscanthus sinensis is a closely related species with substantial genetic diversity, amenable to seed propagation and broadly distributed across a range of environments in eastern Asia including Japan. Forty-three wild Japanese M.sinensis populations collected across a range of latitudes (from N31 degrees 30 in southern to N44 degrees 30 northern Japan) and altitudes (0-1375m) were evaluated in Sapporo (N43 degrees; 56m), Japan to assess morphological traits, winter survival and biomass productivity (BP). Seventy percent of M.sinensis from Hokkaido Island and 67% from other areas of Japan survived over three winter seasons in Sapporo. M.sinensis populations from cooler climates and higher elevations in other areas of Japan showed greater number of tillers, plant height and leaf length whose characteristics were associated with high BP. BP varied among accessions with higher potential productivity in plants from other areas of Japan than from Hokkaido, but annual biomass yield increase is less in the other Japan group. The present study concludes that wild M.sinensis populations from other areas of Japan could be used for domestication as an energy crop in cold environment areas such as Hokkaido. With the observed variability that exists among wild populations, further genetic improvement of M.sinensis for high yield and stability in BP is feasible.
  • 当真 要, 岩本 玲奈, 稲吉 佳緒里
    日本土壌肥料学雑誌 86 2 89 - 97 日本土壌肥料学会 2015年04月 [査読無し][通常論文]
     
    レンコンの栽培は収穫時に多大な労力が必要なことが問題となっている.近年確立された省力で収穫が可能な浅床栽培法を用いてハスの栽培を行い,生育・収量・土壌化学性の変化および灌漑水量について評価を行った.2012年と2013年に,作土を10cmに充填した枠を用い化学肥料(C区)または有機肥料(O区)を用いた2処理区を設けた.窒素とリンの施用量はC区とO区で同等であったが,O区には油かすと鶏糞を用いたためにカリウムはC区の3割程度であった.肥大茎の収穫量(3.15〜3.93kgm^<-2>)は処理区間の違いはなく,一般的な栽培体系での収量より大きかった.一方,C区で一節あたり100〜200gがO区よりも多くなる傾向が見られた.ハスに吸収されたカリウムの約50%が肥大茎にあったことから,カリウム施用量が多いC区で肥大茎の生長に影響したと考えられた.肥大茎の色は2013年が2012年よりも有意に白かった.これは非栽培期間に土壌を湛水状態に保ったため2013年の栽培期の土壌がより還元的になり,肥大茎に付着する酸化鉄が減少したためと考えられた.陽イオン交換容量,土壌全炭素・窒素含量および交換性カリウム含量は2作付け後に14〜55%低下しており,有機物の施用などによって土壌有機物の分解やハスの生長による土壌養分の減少を補う必要がある.栽培に必要な灌漑水量は1,000mm程度であり比較的水の必要量は少なかったが,7〜9月の繁茂期には蒸発散量が降水量を上回るために灌漑が必要である.以上より,浅床栽培法によるハスの省力栽培は収量の増加や品質の向上が見込まれるが,土壌肥沃度を保つために有機物施用等を含めた栽培体系の確立が必要であることが明らかとなった.
  • Ryusuke Hatano, Yo Toma, Yohei Hamada, Hironori Arai, Helena Lina Susilawati, Kazuyuki Inubushi
    Tropical Peatland Ecosystems 339 - 351 2015年01月01日 [査読有り][通常論文]
     
    Results of observations in Central Kalimantan, Indonesia clearly indicate that land use changes caused by drainage, fire, and agricultural practices change the methane (CH4) and nitrous oxide (N2O) emissions from tropical peatlands significantly. The CH4 emissions were higher in burned area and croplands than in natural forests. The N2O emissions were considerably higher in croplands than in natural forests, although there were no significant differences in N2O emissions between burned areas and natural forests. In croplands, the N2O flux was significantly correlated with the carbon dioxide (CO2) flux. However, the CO2 flux in croplands was not correlated with microbial biomass carbon (MBC), while this was significantly correlated in forests. These results indicate that agricultural land use of tropical peatlands varied the controlling factors of the greenhouse gas emissions through microbial activities. Peat fires were also a significant source of CH4 and N2O as well as CO2. Linear correlations of the concentrations of CH4, N2O, and also carbon monoxide (CO) to CO2 indicated that the molar ratios of CO, CH4 and N2O to CO2 in the gas emissions through peat combustion are 0.382, 0.0261 and 0.000156, respectively.
  • 当真 要, 岩本 玲奈, 稲吉 佳緒里, 長崎 信行, 上野 秀人
    愛媛大学農学部農場報告 = Bulletin of the Experimental Farm, Faculty of Agriculture, Ehime University 36 7 - 20 愛媛大学農学部附属農場 2014年09月 [査読無し][通常論文]
     
    レンコンの栽培は収穫時に多大な労力が必要なことが問題となっている。近年確立された省力で収穫が可能な浅床栽培法を用いてハスの栽培を行い、生育・収量・土壌化学性の変化および灌漑水量について評価を行った。2012年と2013年に、作土を10cmに充填した枠を用い化学肥料(C区)または有機肥料(O区)を用いた2処理区を設けた。窒素とリンの施用量はC区とO区で同等であったが、O区には油かすと鶏糞を用いためにカリウムはC区の3割程度であった。肥大茎の収穫量(3.15～3.93kg m-2)は処理区間の違いはなく、一般的な栽培体系での収量より大きかった。一方、C区で一節あたり100～200gがO区よりも多くなる傾向が見られた。ハスに吸収されたカリウムの約50%が肥大茎にあったことから、カリウム施用量が多いC区で肥大茎の生長に影響したと考えられた。肥大茎の色は2013年が2012年よりも有意に白かった。これは非栽培期間に土壌を湛水状態に保ったため2013年の栽培期の土壌がより還元的になり、肥大茎に付着する酸化鉄が減少したためと考えられた。陽イオン交換容量、土壌全炭素・窒素含量および交換性カリウム含量は2作付け後に14～55%低下しており、有機物の施用などによって土壌有機物の分解やハスの生長による土壌養分の減少を補う必要がある。栽培に必要な灌漑水量は1,000mm程度であり比較的水の必要量は少なかったが、7～9月の繁茂期には蒸発散量が降水量を上回るために灌漑が必要である。以上より、浅床栽培法によるハスの省力栽培は収量の増加や品質の向上が見込まれるが、土壌肥沃度を保つために有機物施用等を含めた栽培体系の確立が必要であることが明らかとなった。
  • Takahiro Anan, Shuichi Shimma, Yo Toma, Yasuyuki Hashidoko, Ryusuke Hatano, Michisato Toyoda
    ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS 16 12 2752 - 2757 2014年 [査読無し][通常論文]
     
    Many miniaturized mass spectrometers used for on-site analysis have been designed and developed recently utilizing a broad range of analyzer platforms. These instruments are expected to have widespread applications covering many fields of interest. In our laboratory, a miniaturized multi-turn time-of-flight (TOF) mass spectrometer "MULTUM-S II" was designed and constructed. The size and weight of the developed "MULTUM-S II" are 45 cm x 23 cm x 64 cm and 36 kg. Irrespective of this small platform, it still boasts a high mass resolution capability of more than 30 000. In this study, we attempted to carry out real-time monitoring of gaseous compounds such as N-2, O-2, CO2, N2O and CH4. Using conventional miniaturized mass spectrometers, CO2 and N2O cannot be detected simultaneously due to the low mass resolution inherent to these established analyzer designs. Using a new method, "GC/high resolution mass spectrometry" described in this paper, real time monitoring of gases emitted from soils can be achieved. In a soil incubation experiment, CO2 and N2O started to increase just after water supplement and these gases varied similarly during the experiment, thus showing that this improved gas analyzing system could monitor the short time response of gaseous production in soil.
  • Yo Toma, John Clifton-Brown, Shinji Sugiyama, Makoto Nakaboh, Ryusuke Hatano, Fabian G. Fernandez, J. Ryan Stewart, Aya Nishiwaki, Toshihiko Yamada
    GLOBAL CHANGE BIOLOGY 19 6 1676 - 1687 2013年06月 [査読無し][通常論文]
     
    Global soil carbon (C) stocks account for approximately three times that found in the atmosphere. In the Aso mountain region of Southern Japan, seminatural grasslands have been maintained by annual harvests and/or burning for more than 1000years. Quantification of soil C stocks and C sequestration rates in Aso mountain ecosystem is needed to make well-informed, land-use decisions to maximize C sinks while minimizing C emissions. Soil cores were collected from six sites within 200km2 (767937m asl.) from the surface down to the k-Ah layer established 7300years ago by a volcanic eruption. The biological sources of the C stored in the Aso mountain ecosystem were investigated by combining C content at a number of sampling depths with age (using 14C dating) and 13C isotopic fractionation. Quantification of plant phytoliths at several depths was used to make basic reconstructions of past vegetation and was linked with C-sequestration rates. The mean total C stock of all six sites was 232Mg Cha1 (28417Mg Cha1), which equates to a soil C sequestration rate of 32kg Cha1yr1 over 7300years. Mean soil C sequestration rates over 34, 50 and 100years were estimated by an equation regressing soil C sequestration rate against soil C accumulation interval, which was modeled to be 618, 483 and 332kg C ha1yr1, respectively. Such data allows for a deeper understanding in how much C could be sequestered in Miscanthus grasslands at different time scales. In Aso, tribe Andropogoneae (especially Miscanthus and Schizoachyrium genera) and tribe Paniceae contributed between 64% and 100% of soil C based on 13C abundance. We conclude that the seminatural, C4-dominated grassland system serves as an important C sink, and worthy of future conservation.
  • D. S. Howlett, Y. Toma, H. Wang, S. Sugiyama, T. Yamada, A. Nishiwaki, F. Fernandez, J. R. Stewart
    CATENA 104 127 - 135 2013年05月 [査読無し][通常論文]
     
    Miscanthus, a promising feedstock for the production of lignocellulosic ethanol, will likely see a considerable increase in cultivation and production in the U.S. and Europe in the coming decades. To better predict the effect of this change on soiledaphic resources, we examined a Miscanthus sinensis-dominated grassland in its native range in southern japan. Soil organic carbon age, accumulated carbon stock, and carbon source were determined on pyrolysis volatile (Py-V) and pyrolysis residue (Py-R) fractions of soil organic matter. Stable carbon isotopic composition of soil organic matter was also determined. Values of total sequestered C summed from two soil profiles (0-1.5 m) were 515 and 559 Mg Cha(-1). Stable isotope analysis showed that about 66.8% of soil C, ranging from 52.0 to 84.8%, was derived from C-4 plants. Variation of soil age indicated by C-14 dates of Py-V and Py-R fractions was correlated linearly with soil depths with a R-2 value ranging from 0.98 to 0.99. Phytolith data showed an increase in abundance of M. sinensis and Pleioblastus sect Nezasa following a pyroclastic eruption 7 kyrs ago, and a decrease in Sasa sect. Crassinodi from 12 to 7 kyrs ago. Organic carbon flux ranged from 0.85 to 1.63 Mg Cha(-1) yr(-1) through 1.5-m soil profiles, and Miscanthus-derived carbon flux was distributed in a similar pattern to the total C throughout the soil profiles. Over a 12,000 year history of land use at the Aso caldera, Japan, M. sinensis was found to be a major contributor to soil carbon and a sink for atmospheric CO2, which, under certain constraints, has implications for the potential sequestration of soil carbon under Miscanthus in cultivated conditions. (C) 2013 Elsevier B.V. All rights reserved.
  • 井上恭佑, 当真要, 大久保直樹, 山内孝志, 河野貴幸, 上野秀人
    農作業研究 48 111 - 112 2013年03月 [査読無し][通常論文]
  • 当真 要
    日本土壌肥料学雑誌 84 5 349 - 350 一般社団法人 日本土壌肥料学会 2013年
  • Yo Toma, Kevin Armstrong, J. Ryan Stewart, Toshihiko Yamada, Aya Nishiwaki, Fabian G. Fernandez
    GLOBAL CHANGE BIOLOGY BIOENERGY 4 5 566 - 575 2012年09月 [査読無し][通常論文]
     
    Although Miscanthus sinensis grasslands (Misc-GL) and Cryptomeria japonica forest plantations (Cryp-FP) are proposed bioenergy feedstock systems, their relative capacity to sequester C may be an important factor in determining their potential for sustainable bioenergy production. Therefore, our objective was to quantify changes in soil C sequestration 47 similar to years after a Misc-GL was converted to a Cryp-FP. The study was conducted on adjacent Misc-GL and Cryp-FP located on Mt. Aso, Kumamoto, Japan. After Cryp-FP establishment, only the Misc-GL continued to be managed by annual burning every March. Mass C and N, d13C, and d15N at 030 similar to cm depth were measured in 5 similar to cm increments. Carbon and N concentrations, C:N ratio, d13C, and d15N were measured in litter and/or ash, and rhizomes or roots. Although C input in Misc-GL by M. sinensis was approximately 36% of that in Cryp-FP by C. japonica, mean annual soil C sequestration in Misc-GL (503 similar to kg similar to C similar to ha-1 similar to yr-1) was higher than that in Cryp-FP (284 similar to kg similar to C similar to ha-1 similar to yr-1). This was likely the result of larger C input from aboveground litter to soil, C-quality (C:N ratio and lignin concentration in aboveground litter) and possibly more recalcitrant C (charcoal) inputs by annual burning. The difference in soil d15N between sites indicated that organic C with N had greater cycling between heterotrophic microbes and soil and produces more recalcitrant humus in Misc-GL than in Cryp-FP. Our data indicate that in terms of soil C sequestration, maintenance of Misc-GL may be more advantageous than conversion to Cryp-FP in Aso, Japan.
  • Lauren D. Quinn, J. Ryan Stewart, Toshihiko Yamada, Yo Toma, Masanori Saito, Katsuhisa Shimoda, Fabian G. Fernandez
    BIOENERGY RESEARCH 5 1 139 - 148 2012年03月 [査読無し][通常論文]
     
    Miscanthus sinensis is a moderately invasive ornamental grass species being considered as a bioenergy species in the USA and elsewhere. In this study, we show the range of environmental conditions tolerated by this species in wild populations in the USA and in Japan. Six naturalized populations in the USA and five native populations in Japan were sampled in summer 2009. In each population, environmental factors (canopy cover and soil fertility) were measured, along with measurements of size and morphology for 30 plants. Relationships between M. sinensis size and environmental variables in the two countries were determined using linear mixed effects models. Results indicated that M. sinensis can tolerate extremely wide variation in soil and climate conditions in the populations we sampled across both ranges, suggesting that it could be successfully grown across a wide distribution in the USA, both intentionally as a bioenergy crop and unintentionally as an escaped invader. Plant size generally responded to different environmental conditions in both ranges, with USA plants being negatively influenced by canopy cover and Japanese plants being positively influenced by soil fertility measures. We recommend caution in growing M. sinensis for bioenergy or ornamental purposes to minimize escape outside of its native range.
  • Yo Toma, Fumiaki Takakai, Untung Darung, Kanta Kuramochi, Suwido H. Limin, Salampak Dohong, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 57 3 436 - 451 2011年06月 [査読無し][通常論文]
     
    Our previous research showed large amounts of nitrous oxide (N2O) emission (>200 kg N ha(-1) year(-1)) from agricultural peat soil. In this study, we investigated the factors influencing relatively large N2O fluxes and the source of nitrogen (N) substrate for N2O in a tropical peatland in central Kalimantan, Indonesia. Using a static chamber method, N2O and carbon dioxide (CO2) fluxes were measured in three conventionally cultivated croplands (conventional), an unplanted and unfertilized bare treatment (bare) in each cropland, and unfertilized grassland over a three-year period. Based on the difference in N2O emission from two treatments, contribution of the N source for N2O was calculated. Nitrous oxide concentrations at five depths (5-80 cm) were also measured for calculating net N2O production in soil. Annual N fertilizer application rates in the croplands ranged from 472 to 1607 kg N year-1. There were no significant differences in between N2O fluxes in the two treatments at each site. Annual N2O emission in conventional and bare treatments varied from 10.9 to 698 and 6.55 to 858 kg N ha I year I, respectively. However, there was also no significant difference between annual N2O emissions in the two treatments at each site. This suggests most of the emitted N2O was derived from the decomposition of peat. There were significant positive correlations between N2O and CO, fluxes in bare treatment in two croplands where N-2O flux was higher than at another cropland. Nitrous oxide concentration distribution in soil measured in the conventional treatment showed that N2O was mainly produced in the surface soil down to 15 cm in the soil. The logarithmic value of the ratio of N2O flux and nitrate concentration was positively correlated with water filled pore space (WEPS). These results suggest that large N2O emission in agricultural tropical peatland was caused by denitrification with high decomposition of peat. In addition, N2O was mainly produced by denitrification at high range of WFPS in surface soil.
  • Yo Toma, Fabian G. Fernandez, Syohei Sato, Miki Izumi, Ryusuke Hatano, Toshihiko Yamada, Aya Nishiwaki, German Bollero, J. Ryan Stewart
    GLOBAL CHANGE BIOLOGY BIOENERGY 3 2 116 - 134 2011年04月 [査読無し][通常論文]
     
    Species in the Miscanthus genus have been proposed as biofuel crops that have potential to mitigate elevated atmospheric carbon dioxide (CO(2)) levels and nitrous oxide (N(2)O) and methane (CH(4)) emissions. Miscanthus sinensis is widespread throughout Japan and has been used for biomass production for centuries. We assessed the carbon (C) budget and N(2)O and CH(4) emissions over the growing season for 2 years in a M. sinensis-dominated grassland that was naturally established around 1972 in Tomakomai, Hokkaido, Japan, which is near the northern limit for M. sinensis grassland establishment on Andisols. Average C budget was -0.31 Mg C ha-1, which indicates C was released from the grassland ecosystem to the atmosphere. Dominant components in the C budget appeared to be aboveground net primary production of plants (1.94-2.80 Mg C ha-1) and heterotrophic respiration (2.27-3.11 Mg C ha-1). The measurement of belowground net primary production (BNPP) of plants in the M. sinensis grassland was extremely variable, thus only an approximate value could be calculated. Mean C budget calculated with the approximated BNPP value was 1.47 and -0.23 Mg C ha-1 for 2008 and 2009, respectively. Given belowground biomass (9.46-9.86 Mg C ha-1) was 3.1-6.5 times higher than that of aboveground biomass may provide additional evidence suggesting this grassland represents a C sink. Average CH(4) emissions across years of -1.34 kg C ha-1 would indicate this grassland acts as an atmospheric CH(4) sink. Furthermore, average N(2)O emissions across years were 0.22 kg N ha-1. While the site may contribute N(2)O to the atmosphere, this value is lower compared with other grassland types. Global warming potential calculated with the approximated BNPP value was -5.40 and 0.95 Mg CO(2) Eq ha-1 for 2008 and 2009, respectively, and indicates this grassland could contribute to mitigation of global warming.
  • Anzoua Kossonou Guillaume, 当真 要, 飯塚 菜摘, 山田 敏彦
    バイオマス科学会議発表論文集 6 44 - 45 一般社団法人日本エネルギー学会 2011年 
    This study evaluated the genetic variability and biomass potential (BP) of susuki (Miscanthus sinensis) in cool region as border of habitat area. 43 M. sinensis accessions collected throughout Japan were transplanted side-by-side in field in 2007 in cool season condition and, harvested in late autumn of 2008 and 2009. Accessions (67%) could survive until the third year. For accessions from Hokkaido region, plant morphology varied less between different locations of Hokkaido. Combined with accessions from other regions it varied and vigorous morphology was observed some accessions from warm region. Consequently, morphological difference affected greatly BP which was inferior (42%) with accessions from Hokkaido than others from warn regions. Much genetic variability would be useful for breeding program of Miscanthus adaptable cool environment.
  • Aya Nishiwaki, Aki Mizuguti, Shotaro Kuwabara, Yo Toma, Genki Ishigaki, Tomomi Miyashita, Toshihiko Yamada, Hiroya Matuura, Sachi Yamaguchi, A. Lane Rayburn, Ryo Akashi, J. Ryan Stewart
    AMERICAN JOURNAL OF BOTANY 98 1 154 - 159 2011年01月 [査読無し][通常論文]
     
    Premise of the study : Looming petroleum shortages and projected negative impacts of human-induced climate change may be partly alleviated by the development and use of bioenergy feedstock crops. Miscanthus x giganteus, a highly productive sterile triploid hybrid grass that was discovered in Japan several decades ago, has considerable potential as an alternative source of energy. Given the risks, however, involved in the reliance upon production of one clone of this hybrid, which is a natural cross between Miscanthus sacchariflorus and Miscanthus sinensis, for lignocellulosic bioenergy production, natural occurrences of triploidy were investigated in sympatric populations of tetraploid M. sacchariflorus and diploid M. sinensis in Japan. Methods : Seeds were counted and DNA content was estimated by flow cytometry for plants of M. sacchariflorus and M. sinensis in several sympatric populations throughout Japan. Chromosomes were also counted for select plants. Key results : Based on seed-set data, M. sacchariflorus has significantly lower seed set than M. sinensis in Japan. Putative triploid seeds were found on M. sacchariflorus plants in southern Japan. Conclusions : This is the first report of the natural occurrence of Miscanthus triploid plants in several decades. If found to be sterile and similar in productivity to the commonly cultivated clone of M. x giganteus, these triploid plants might serve as additional sources of genetic variation for bioenergy production. Seed set data also indicates that other triploid plants might be found in more northern regions of Japan.
  • Kossonou Guillaume Anzoua, Yasuhisa Kajihara, Yo Toma, Natsumi Iizuka, Toshihiko Yamada
    Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy 90 1 59 - 65 2011年 [査読無し][通常論文]
     
    It is planned to increase plant biomass feedstock to sustain the renewable energy source, bioenergy. In cool regions such as Hokkaido which often offers a short and stressful growth season, less is known about biomass potential (BP) in plants, and generally there is a lack of data regarding a regional suitable harvesting system in feedstock. A constant supply of feedstock per month using several biomass plants would be important for establishing an all year round operating system (AYROS) in biofuel production. Two types of perennial lignocellulosic crops, four C3 grasses which adapt well to cool environments, orchardgrass (OG), reed canarygrass (RC), tall fescue (TF) and timothy (TI), referred to as cool season grasses (CSG) and C4 native grass, Miscanthus sinensis called 'susuki', were evaluated for the BP in Sapporo, Japan. CSG were sown into fertilized land in 2006, whilst M. sinensis was planted in 2007 without fertilization. Three years after planting, in 2009, regional potential across all harvesting of CSG was 9.7 t ha-1. year-1. Different harvestings of CSG revealed high BP from RC and TI rather than OG and TF. RC showed BP peaks twice, in June (11 ± 0.45 t ha-1 year-1) and September (15 ± 1.11 t ha -1 year-1), and a single peak in July (15 ± 1.99 t ha-1 year -1) for TI, indicating that RC is a two peaks type, whilst TI falls into a one peak type. For M. sinensis, the BP increased with the year and varied among accessions. In 2009, regional potential was 1,287 ± 343 g plant-1 year-1. Accessions native to Hokkaido showed maximum BP of 827 ± 353 g plant-1 year -1, mainly from Matsumae (1,622 ± 692 g plant-1 year-1) and Toyoura (2,174 ± 169 g plant-1 year-1). Accessions native to areas other than Hokkaido yielded a potential of 2,206±388 g plant-1 year-1, mainly from Shiozuka (2,531 ± 526 g plant-1 year-1) and Akeno (2,653 ± 635 g plant-1 year-1), substantially higher than the BP of Hokkaido accessions. The BP of M. sinensis over two years of 9 accessions in the present study was about 36.9 t ha-1 year -1, by converting biomass data of plant (921.4 g plant-1 year-1) to land area unit. The BP experiment estimates biomass feedstock is supplied with 10-15 t ha-1 by harvesting TI and RC in June to September and 30 t ha-1 by harvesting M. sinensis in October. This study demonstrated the feasibility and advantage of the combination of CSG and M. sinensis. The BP could be improved using mostly superior genotypes of M. sinensis selected from areas other than Hokkaido. The information from the present study will be available for establishing AYROS in feedstock production for biofuels such as bioethanol in cool regions such as Hokkaido.
  • Yo Toma, Sonoko D. Kimura, Hiroyuki Yamada, Yuu Hirose, Kazuya Fujiwara, Kanako Kusa, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 56 4 663 - 675 2010年08月 [査読無し][通常論文]
     
    Soil is an important source of atmospheric carbon dioxide (CO2) and nitrous oxide (N2O). Studies of CO2 and N2O emissions from bare soil may explain annual changes in carbon (C) in soil organic matter (SOM) and help analyze N2O production from SOM. Therefore, CO2 and N2O emissions associated with the decomposition of SOM from bare soil are important factors for assessing the C budget and N2O emission in agricultural fields. We conducted a study over 7 years to assess the controlling factors of CO2 and N2O emissions from unplanted and unfertilized soil in Mikasa, Hokkaido, Japan. The CO2 flux increased in summer and there were significant positive correlations between the CO2 flux and soil temperature in the first 4 years. However, apparent relationships between CO2 flux and water-filled pore space, soil NH4 and NO3 concentrations were not observed. The slope of monthly CO2 emission against mean monthly temperature was positively correlated with monthly precipitation. These results suggest that the response of CO2 production to increases in soil temperature became more sensitive in wet soils. The average CO2 emission during the study period was 2.53 Mg C ha-1 year-1, and uncertainty in the annual CO2 emission was 24%. Annual precipitation explained the yearly variation (CO2 emission [Mg C ha-1 year-1] = 0.0021 x annual precipitation [mm year-1] -0.0499, R = 0.976, P < 0.001). Nitrous oxide flux increased from July to October and was positively correlated with CO2 flux. Based on the ratio of N2O-N : NO-N of fluxes, N2O appeared to be the main product of denitrification. The average N2O emission over the study period was 4.88 kg N ha-1 year-1, and uncertainty in the annual N2O emission was 58.5%. Strong relationships between the monthly emissions of CO2 and N2O suggest that N2O production by denitrification is strongly affected by SOM decomposition. Unlike CO2 emission, a relationship between N2O emission and precipitation was not observed because of the multiple pathways of nitrification and denitrification for N2O production induced by SOM decomposition.
  • Aboveground plant biomass, carbon, and nitrogen dynamics before and after burning in a seminatural grassland of Miscanthus sinensis in Kumamoto, Japan.
    27. TOMA Yo, FERNÁNDEZ G. Fabián, NISHIWAKI Aya, YAMADA Toshihiko, BOLLERO Germán, STEWART J. Ryan
    Global Change Biology Bioenergy 2 52 - 62 2010年05月 [査読有り][通常論文]
  • Anzoua Kossonou Guillaume, 梶原 靖久, 当真 要, 飯塚 菜摘, 山田 敏彦
    バイオマス科学会議発表論文集 5 28 - 29 一般社団法人日本エネルギー学会 2010年 
    This study aims to establish a potential biomass feedstock for year round operation system for biofuel production in cool regions. Harvesting time of four cool season grasses timothy (TI), reed canarygrass (RC), orchardgrass (OG) and tall fescue (TF) were combined with that of susuki (Miscanthus sinensis). The combination revealed that TI and RC were able to provide a monthly supply of 50,000t from June to October. Thereafter, M. sinensis was able to ensure similar amount from November to May, corresponding 18,500KL ethanol monthly production.
  • Sonoko D. Kimura, Yo Toma, Zhijian Mu, Hiroyuki Yamada, Ryusuke Hatano
    SUSTAINABILITY SCIENCE 5 1 19 - 27 2010年01月 [査読無し][通常論文]
     
    Relationships among global warming potential (GWP), farmland surplus nitrogen (FSN) and income for major land uses in the Ikushunbetsu watershed were compared using the eco-balance method. An empirical model was created for carbon dioxide, methane and nitrous oxide for both uplands and paddy rice using monitoring data from 22 fields. The greenhouse gas emissions were converted into GWP, whereas yield and FSN were obtained from interviews with farmers and a literature survey. Land use distribution was obtained by ground surveys in 2002, 2005 and 2007. The analysis showed that paddy rice and soybeans were characterized by a high GWP, low FSN and high income, whereas onions and vegetables had a high FSN but low GWP and moderate income. Wheat showed a negative GWP in some years, and abandoned areas always exhibited negative values. The total GWPs for the region were 14,184, 11,085 and 8,337 Mg CO(2) year(-1) for 2002, 2005 and 2007, respectively. The contribution of paddy rice to GWP was highest, ranging from 40 to 75%. To find optimal land use combinations that provide higher incomes and lower GWPs and FSNs than at present, all possible land use combinations were analyzed by changing the land use proportion from 0 to 100% at an interval of 10%. The number of land use combinations meeting the requirements in the three investigated years was 205. Abandoned area, which had the smallest environmental load, was included in every land use combination, indicating that land uses with low environmental impacts should be maintained at a certain proportion to mitigate the environmental load accompanying land uses with high production.
  • The ecology and agronomy of Miscanthus sinensis, a species important to bioenergy crop development, in its native range in Japan: a review.
    29. STEWART J. Ryan, TOMA Yo, FERNÁNDEZ G. Fabián, NISHIWAKI Aya, YAMADA Toshihiko, BOLLERO Germán
    Global Change Biology Bioenergy 1 126 - 153 2009年06月 [査読有り][通常論文]
  • Zhijian Mu, Sonoko D. Kimura, Yo Toma, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 54 4 650 - 661 2008年08月 [査読無し][通常論文]
     
    To evaluate the carbon budget in soils under different cropping systems, the carbon dioxide (CO(2)) flux from soils was measured in a total of 11 upland crop fields within a small watershed in central Hokkaido over the no snow cover months for 3 years. The CO, flux was measured using a closed chamber method at bare plots established in each field to estimate soil organic matter decomposition. Temporal variation in instantaneous soil CO(2) fluxes within the sites was mainly controlled by soil temperature and moisture. Annual mean CO, fluxes and cumulative CO(2) emissions had no significant relationship with soil temperature and moisture (P > 0.2). However, there was a significant quadratic relationship between annual mean CO(2) flux or cumulative CO, emission and soil clay plus silt content (%) (R(2) = 0.72-0.74, P < 0.0003). According to this relationship, the optimum condition for soil CO, emission is at a clay plus silt content of 63%. The cumulative CO, emission during the no snow cover season within each year varied from 1,159 to 7,349 kg C ha(-1) at the different sires. The amount of crop residue carbon retained in the soils following a cropping season was not enough to offset the CO, emission from soil organic matter decomposition at all sites. As a consequence, the calculation of the soil carbon budget (i.e. the difference between the carbon added as crop residues and compost and the carbon lost as CO, from organic matter decomposition) ranged from -7,349 to -785 kg C ha(-1), except for a wheat site where a positive value of 4,901 kg C ha(-1) was observed because of a large input of organic carbon with compost. The negative values of the soil carbon budget indicate that these cropping systems were net sources of atmospheric CO(2).
  • 木村 園子ドロテア, 当真 要, 山田 浩之, 木 志堅, 波多野 隆介
    日本地球化学会年会要旨集 55 117 - 117 日本地球化学会 2008年 
    本報告では、地域レベルにおいて温室効果ガス放出量の推定方法を作成し、その推定方法を用い、土地利用の変化による地球温暖化ャeンシャル削減策をエコバランス評価によって解析した。2002年から2007年にかけて、この流域内において21の圃場（9種の土地利用、延べ47地点・年）において、クローズドチャンバー法によりメタン、亜酸化窒素および二酸化炭素フラックスを測定した。ガスフラックスは、土壌環境因子および肥矧ﾇ理因子によってパラメタリゼーションし、年間放出量を推定した。
  • Yasuyuki Hashidoko, Fumiaki Takakai, Yo Toma, Untung Darung, Lulie Melling, Satoshi Tahara, Ryusuke Hatano
    SOIL BIOLOGY & BIOCHEMISTRY 40 1 116 - 125 2008年01月 [査読無し][通常論文]
     
    Using a soilless culture system mimicking tropical acidic peat soils, which contained 3mg of gellan gum and 0.5mgNO(3)(-)-N per gram of medium, a greenhouse gas, N2O emitting capability of microorganisms in acidic peat soil in the area of Palangkaraya, Central Kalimantan, Indonesia, was investigated. The soil sampling sites included a native swamp forest (NF), a burnt forest covered by ferns and shrubs (BF), three arable lands (A-1, A-2 and A-3) and a reclaimed grassland (GL) next to the arable lands. An acid-tolerant Janthinobacterium sp. strain Al-13 (Oxalobacteriaceae, beta-proteobacteria) isolated from A-I soil was characterized as one of the most prominent N2O-emitting bacteriain this region. Physiological characteristics of the N2O emitter in the soilless culture system, including responses to soil environments, substrate concentration, C-source concentration, pH, and temperature, suggest that the N2O emitting Janthinobacterium sp. strain Al-13 is highly adapted to reclaimed open peatland and primarily responsible for massive N2O emissions from the acidic peat soils. Regulation of N2O emitters in the reclaimed peatland for agricultural use is therefore one of the most important issues in preventing the greenhouse gas emission from acidic peat soil farmlands. (c) 2007 Elsevier Ltd. All rights reserved.
  • Mu Zhijian, Sonoko D. Kimura, Yo Toma, Ryusuke Hatano
    JOURNAL OF ENVIRONMENTAL SCIENCES 20 11 1312 - 1322 2008年 [査読無し][通常論文]
     
    Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November), for three years, in a total of 11 upland crop fields in central Hokkaido, Japan. The annual mean N2O fluxes ranged from 2.95 to 164.17 mu gN/(m(2).h), with the lowest observed in a grassland and the highest in an onion field. The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall events around harvesting in autumn. No clear common factor regulating instantaneous N2O fluxes was found at any of the study sites. Instead, instantaneous N2O fluxes at different sites were affected by different soil variables. The cumulative N2O emissions during the study period within each year varied from 0.15 to 7.05 kgN/hm(2) for different sites, which accounted for 0.33% to 5.09% of the applied fertilizer N. No obvious relationship was observed between cumulative N2O emission and applied fertilizer N rate (P > 0.4). However, the cumulative N2O emission was significantly correlated with gross mineralized N as estimated by CO2 emissions from bare soils divided by C/N ratios of each soil, and with soil mineral N pool (i.e., the sum of gross mineralized N and fertilizer N) (P < 0.001).
  • Yo Toma, Sonoko D. Kimura, Yuu Hirose, Kanako Kusa, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 53 5 692 - 703 2007年10月 [査読無し][通常論文]
     
    Variability in the emission factors of nitrous oxide (N2O) associated with the application of chemical fertilizer (EFF) and organic matter (EFO) were analyzed in two onion fields (GL, Gray Lowland soil [Gleysol; Food and Agriculture Organization/UNESCO]; BL, Brown Lowland soil [Fluvisol; Food and Agriculture Organization/UNESCO]) in Mikasa, Hokkaido, Japan. Nitrous oxide flux was measured using a closed chamber technique in four treatments (FOP, chemical nitrogen fertilization and organic matter application, with plants; F, chemical nitrogen fertilization only, without plants; OP, organic matter application only, with plants; C, control, no fertilization or organic matter application, without plants) for 4 years in GL (2000, 2003-2005) and for 1 year in BL (2005). The application rate of chemical fertilizer nitrogen ranged from 237 to 242 kg N ha(-1) year(-1) in GL and was 284 kg N ha(-1) year(-1) in BL; organic matter nitrogen ranged from 81 to 117 kg N ha(-1) year(-1) in GL and was 181 kg N ha(-1) year(-1) in BL. The emission factors (EF) were calculated using the equations: EFF (%) = (N2O emission in FOP-N2O emission in OP)/(applied chemical nitrogen fertilizer) x 100 and EFO (%) = (N2O emission in FOP-N2O emission in F)/(applied organic matter nitrogen) x 100. The annual N2O emissions for treatments FOP, F, OP and C were 7.2-17, 5.7-17, 3.2-9.9 and 2.0-12 kg N ha(-1) year(-1), respectively, in GL and 5.6, 2.8, 1.9 and 1.8 kg N ha(-1) year(-1), respectively, in BL. The EFF ranged from 1.3% to 5.5% in GL and was 1.3% in BL. The EFF was positively correlated with the mean annual air temperature (P < 0.01), suggesting that N2O emission derived from chemical nitrogen fertilizer increases as air temperature rises. The EFO, however, differed greatly between GL (ranging from -5.2% to 9.1%) and BL (1.5%). The EFO was positively correlated with the mean annual relative humidity, although the correlation was not significant (P = 0.23). This finding suggests that much wetter climatic conditions may increase N2O emissions derived from organic matter nitrogen. The estimated N2O emissions based on these EF values and the rate of nitrogen application coincided well with the measured N2O emissions in the FOP treatment in both soils.
  • Sonoko D. Kimura, Zhijian Mu, Yo Toma, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 53 4 373 - 386 2007年08月 [査読無し][通常論文]
     
    This study quantified and evaluated the greenhouse gas emissions of farmland soils at a watershed scale using parameters available at a regional scale. The estimation was based on field monitoring data in the Ikushunbetsu River Watershed, Hokkaido, Japan. Simple regression models were created for carbon dioxide, nitrous oxide and methane emissions associated with six major agricultural land uses, and forest as an alternative land use to farmland. An eco-balance method involves conducting an analysis on the basis of farmland surplus nitrogen (N) and global warming potential (GWP). Uncertainties associating the estimations were estimated using Mote Carlo simulation. The eco-balance is the analysis of the relationship between production and environmental load. In this study, production and environmental load were compared by changing each of the land use combinations by 10%. Farmland surplus N was lowest for soybean with 8.2 kg N ha(-1) year(-1), followed by paddy rice. The highest value was recorded for vegetables with 99.8 kg N ha(-1) year(-1). The weighted mean of total farmland based on the land use proportion was 44 +/- 33.8 kg N ha-1 year(-1). The calculated GWP was 7.3 Mg CO2 eq ha(-1) year(-1) for paddy rice and 0.1 to 6.8 Mg CO2 eq ha(-1) year(-1) for upland crops. The weighted mean of the total farmland area was 4.0 +/- 3.4 Mg CO2 eq ha(-1) year(-1). The eco-balance analysis showed that there were 59 combinations out of 8008 combinations able to reduce GWP more than 6%, but less than 7%, than the value in 2005. Among them, in 30 combinations, farmland surplus N became less than the value in 2005; production was reduced compared with the value in 2005 in 27 combinations. Soybean occupied 20-80% in the seven combinations where production was increased compared with 2005, while keeping farmland surplus N below the value in 2005. The estimation of greenhouse gases in this study exhibited high uncertainty because of variability in management and errors in evaluation procedures. Quantification of the data variability is set at maximum, which comprises the measured values in this area. Based on the quantification of the uncertainty, more efficient quantification methods can be established to clarify mitigation potential. This type of quantification and comparison between production and emission enables decision makers to set some threshold values that allow a compromise between production and environmental load.
  • Yo Toma, Ryusuke Hatano
    SOIL SCIENCE AND PLANT NUTRITION 53 2 198 - 205 2007年04月 [査読無し][通常論文]
     
    We studied the effect of crop residues with various C:N ratios on N2O emissions from soil. We set up five experimental plots with four types of crop residues, onion leaf (OL), soybean stem and leaf (SSL), rice straw (RS) and wheat straw (WS), and no residue (NR) on Gray Lowland soil in Mikasa, Hokkaido, Japan. The C:N ratios of these crop residues were 11.6, 14.5, 62.3, and 110, respectively. Based on the results of a questionnaire survey of farmer practices, we determined appropriate application rates: 108, 168, 110, 141 and 0 g C m(-2) and 9.3, 11.6, 1.76, 1.28 and 0 g N m(-2), respectively. We measured N2O, CO2 and NO fluxes using a closed chamber method. At the same time, we measured soil temperature at a depth of 5 cm, water-filled pore space (WFPS), and the concentrations of soil NH4+-N, NO3--N and water-soluble organic carbon (WSOC). Significant peaks of N2O and CO2 emissions came from OL and SSL just after application, but there were no emissions from RS, WS or NR. There was a significant relationship between N2O and CO2 emissions in each treatment except WS, and correlations between CO2 flux and temperature in RS, soil NH4+-N and N2O flux in SSL and NR, soil NH4+-N and CO2 flux in SSL, and WSOC and CO2 flux in WS. The ratio of N2O-N/NO-N increased to approximately 100 in OL and SSL as N2O emissions increased. Cumulative N2O and CO2 emissions increased as the C:N ratio decreased, but not significantly. The ratio of N2O emission to applied N ranged from -0.43% to 0.86%, and was significantly correlated with C:N ratio (y = -0.59 ln [x] + 2.30, r(2) = 0.99, P < 0.01). The ratio of CO2 emissions to applied C ranged from -5.8% to 45% and was also correlated with C:N ratio, but not significantly (r(2) = 0.78, P = 0.11).

MISC

書籍等出版物

  • 波多野, 隆介, 森, 昭憲 (農学) (担当:分担執筆範囲:半自然草地の炭素固定と温室効果ガス動態)
    海青社 2024年08月 (ISBN: 9784860994013) 211p, 図版 [3] p
  • The Soils of Japan
    Yo Toma (担当:分担執筆範囲:9.2.5 Grassland)
    Springer 2020年12月
  • 改訂 土壌学概論
    当真要 (担当:分担執筆範囲:地域・地球環境への負荷と緩和)
    朝倉書店 2020年10月
  • Tropical Peatland Ecosystems
    Ryusuke Hatano, Yo Toma, Yohei Hamada, Hironori Arai, Helena Lina Susilawati, Kazuyuki Inubushi (担当:分担執筆範囲:Methane and Nitrous Oxide Emissions from Tropical Peat Soil)
    Springer 2016年

講演・口頭発表等

担当経験のある科目（授業）

  • 農場実習Ⅰ愛媛大学農学部
  • 植物栄養学愛媛大学農学部
  • 熱帯農学愛媛大学大学院農学研究科
  • 外書講読愛媛大学農学部
  • 土壌管理学特論愛媛大学大学院農学研究科
  • 栽培土壌学愛媛大学農学部
  • 地域環境学特論Ⅰ北海道大学大学院
  • 温暖化影響学総論北海道大学
  • 地学概論北海道大学
  • 物理化学北海道大学
  • 土壌学及び作物栄養学概論北海道大学
  • 土壌学Ⅰ北海道大学
  • 土とはなんだろうか愛媛大学
  • 農場実習Ⅱ愛媛大学農学部
  • 農業生産管理学実習Ⅱ愛媛大学農学部
  • 農業生産管理学実習Ⅰ
  • 資源植物栄養学愛媛大学農学部

所属学協会

  • 土壌物理学会   日本炭化学会   日本農作業学会   日本ペドロジー学会   日本草地学会   日本土壌微生物学会   日本土壌肥料学会   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2022年10月 -2028年03月 
    代表者 : 種田 あずさ, 当真 要, 片柳 薫子
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2022年04月 -2026年03月 
    代表者 : 当真 要
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2021年04月 -2025年03月 
    代表者 : 豊田 正範, 当真 要, 諸隈 正裕, 水田 圭祐
     
    本研究は直播と地下点滴潅がい栽培による水稲－コムギの輪作体系における生産性と温室効果ガス排出量削減による環境負荷低減効果の検証が目的である．本年度は香川大学農学部内の畑地と水田の両試験圃場にて，水稲－コムギ輪作の栽培試験を実施した． 水稲栽培では，畑地圃場の点滴潅がい区に点滴チューブを地表面からの深さ20cmに埋設した．6月15日に種子間隔3cmのシードテープを条間30cmで1畝につき6条を播種した．水田の湛水栽培区には6月17日に株間15cm，条間30cmで移植した．点滴潅がい区の日々の潅水量は推定蒸発散量と作物係数により決定し，降雨の際は適宜潅水を控えた．湛水栽培区は代かきから成熟期の収穫直前まで常時湛水状態とした．生育期間中には地上部乾物重，葉面積，積算吸収日射量，葉齢，茎数，SPAD値などの調査を定期的に実施した．点滴潅がい区の全乾物重，全籾数，穂数は湛水栽培区を上回っていたが，登熟歩合，玄米千粒重，収穫指数は湛水栽培区より低かったため，結果的に収量は湛水栽培区と同水準となった． 生育期間中は毎週1回，圃場から排出される二酸化炭素（CO2），亜酸化窒素（N2O），メタン（CH4）フラックスをチャンバー法により測定した． 水稲の収穫後にコムギ品種さぬきの夢の栽培を実施した．畑地圃場と水田の前作跡に裁断した前作の稲わらを散布して耕運機で浅く耕起し，種子間隔2.5cmのシードテープを条間25cmで播種した．播種日は畑地圃場が11月16日，水田が11月18日である．畑地圃場では播種作業は順調で，発芽，苗立は良好であった．一方，水田では播種時に土壌が過湿状態で発芽，苗立も不良であった．このため，水田では比較的発芽が揃っている一部区画のみを調査対象としている．成熟と収穫時調査は5月下旬の見込みであり，その後，できるだけ速やかに水稲栽培を開始する予定である．
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 豊田 岐聡, 中山典子, 古谷浩志, 当真要
     
    昨年度に引き続き，マルチターン飛行時間型質量分析計「MULTUM（製品名infiTOF）」を用いた「濃度差が6桁に及ぶ土壌ガス4成分の同時連続フラックス測定システム」 を構築し，7成分の無機・有機ガス(N2・O2・CO2・ N2O・NO・CH4・C2H4)を同時に長期間連続測定できるように，制御系，ソフトウェアの改良を行った．特に，昨年度購入した新型infiTOFの制御系ならびにデータ取得系を，オンサイトでの土壌ガス測定に適したものにする改良を進めた．以前から用いているものとは大きく電源などのシステムが異なっているため，順を追って改良を進めている， また，これまでは土壌表面に発生するガスをチャンバー法で分析していたが，本研究の目的である土壌内部の生態系起源ガスの挙動を捉えるためポーラスチューブを用いた土壌内部のガス採取法の開発を新たに行った．土壌中の水分がガスサンプリング系に入り込まないように，市販されている散水用のポーラスチューブを用いることとした．チューブを地中に埋め，チューブ中に拡散した土壌ガスを，これまでのチャンバー法と同様のガス分析系を利用して2分間隔で亜酸化窒素濃度を計測できるシステムを構築した．チューブ内のガスを循環させることで，局所的なガスをサンプリングできるようにした．実際に実験室内で市販されている園芸用の土を用いて評価を行い，土中の亜酸化窒素濃度が，土に水を含ませると1ppm以上発生していることを捉えることに成功した．土壌表面でガスが薄まっている状況と異なり，ガス密度がかなり高いことが分かったため，それに適した系の構築を行った．
  • 日本中央競馬会：畜産振興事業
    研究期間 : 2020年04月 -2022年03月 
    代表者 : 波多野隆介, 倉持寛太, 河合正人, 築城幹典, 当真要, 森昭憲, 金子真, 井原啓貴, 有田敬俊、秋山優希
  • 資源循環と土壌炭素隔離を伴うバイオチャーによる作物増収と温暖化ガス抑制
    ヤンマー資源循環支援機構：
    研究期間 : 2020年04月 -2022年03月 
    代表者 : 当真 要
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2017年04月 -2022年03月 
    代表者 : 上野 秀人, 当真 要
     
    超低投入持続型水稲栽培（緑肥区）における水稲の生育調査、収量及び品質調査を行い、慣行栽培水田（対照区）と比較したところ、収量レベルや品質において両区に有意差はみられなかったが、緑肥区は対照区に比べて栽培開始時期によるバラツキが大きいことが明らかとなった。5月下旬に栽培を開始した緑肥区は、シロクローバーの生育が十分ではなく、固定された窒素量が比較的低かったため、栽培前期の養分吸収が十分ではなく、収量が比較的低くなった。一方、6月中旬に栽培を開始した緑肥区水田の水稲生育は、対照区を上回っており、比較的高収量になることが示された。本栽培体系においては、シロクローバー生育量が、直接窒素供給量に結びつき、その後の水稲生育に非常に大きな影響をもたらすことが明らかになった。 緑肥分解後に生じる土壌還元および緑肥由来炭素によりメタンガスが多量に発生することが問題と考えられるが、緑肥区において中干し時期を1週間早めることにより、メタンガス発生が大幅に減少することを明らかにした。 水稲栽培後に発生する主要な雑草であるスズメノテッポウを4月上旬に採取し、スズメノテッポウ内部に生息するエンドファイト微生物の抽出と16SrDNAアンプリコンによる微生物相の解析を行った。緑肥区の微生物相についてはデータを得ることができ、変動が少ないデータが得られたが、対照区のサンプル処理がうまく行かなかったため、現時点で比較することは難しいと考えられた。 田面水および土壌表層に生息する土壌生物を定期的に採取し、個体数や重量を測定したところ、緑肥区での生物量が多いことを明らかにした。また田面水中の緑藻類の定量を行い、緑肥区で発生量が高い傾向にあることが示された。
  • 岩石と場の特性を活用した風化促進技術“A-ERW”の開発
    国立研究開発法人 新エネルギー・産業技術総合開発機構：ムーンショット型研究開発事業
    研究期間 : 2022年
  • 水田土壌中の多成分ガス濃度測定に基づいた水稲・農地診断イノベーション
    公益財団法人岩谷直治記念財団：岩谷科学技術研究助成
    研究期間 : 2020年04月 -2021年03月 
    代表者 : 中山典子, 豊田岐聡, 古谷浩志, 上野秀人, 当真 要
  • けい酸加里試料の分析及びけい酸加里を用いた栽培実験
    開発肥料株式会社：共同研究
    研究期間 : 2019年04月 -2021年03月 
    代表者 : 大藤弘明, 当真 要
  • クリンカーの堆肥化促進メカニズムの解明と核心的堆肥化技術の開発
    愛媛大学：産学連携推進事業
    研究期間 : 2018年04月 -2019年03月 
    代表者 : 上野秀人, 当真 要
  • レンコン促成栽培を目的とした保温・光利用率向上栽培システムの確立
    愛媛大学：産学連携推進事業
    研究期間 : 2018年04月 -2019年03月 
    代表者 : 当真 要
  • 日本学術振興会：科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2017年06月 -2019年03月 
    代表者 : 豊田 岐聡, 古谷 浩志, 中山 典子, 本堂 敏信, 当真 要
     
    2018年度は、前年度までに構築した可搬型超高分解能質量分析計MULTUMと自動開閉土壌チャンバーを連結させた「6桁濃度が異なる土壌ガスのフラックス測定システム」を愛媛大学農学部附属農場に持ち出し、フィールド観測を2018年9月と2019年3月に計2回実施した。実際に畑から放出される亜酸化窒素と二酸化炭素、およびメタン（2回目のみ）濃度の連続測定を行った。 9月に実施した1回目のフィールド観測では、2分毎のガス濃度測定を、6日間連続で実施した。土壌チャンバーをクローズ状態にした20分間の濃度変化から、1時間に1サイクルでフラックスを求めた。土壌から放出される亜酸化窒素と二酸化炭素のフラックスが、降雨後１時間以内に急激に増加することを初めて捉えることができた。しかし、1回目の観測時点では、亜酸化窒素 について10 ppbv以下の微小な濃度変動を測定する精度を達成できていいなかった。これを改善するため、ガスクロマトグラフィー（GC）部や質量分析計のセッティングを最適化することで、イオン検出強度を3～4倍程度に増強し、また各フラックス測定の前後に標準ガスを挟み込む測定シーケンスに変更することで、感度ドリフトの改善と測定精度向上を果たした。 3月に行った2回目のフィールド観測では、2週間の連続観測を実施した。観測データの解析中であるが、観測経過は順調であり、測定精度の向上ならびに感度ドリフトの補正は想定通り達成された。またフィールド観測中に亜酸化窒素・二酸化炭素・メタンの3種混合標準ガスを用いて、本研究で開発したMULTUM＋自動開閉土壌チャンバー法（大阪大学）と従来法であるGC法（愛媛大学）による相互比較も実施した。両者ともに保証値と良く一致し、開発したMULTUMシステムによる濃度差6桁の異なるガスの同時定量測定の妥当性を確認することができた。
  • 徐放性総合ミネラル剤”CORE”による作物生育改善効果の評価に関する研究
    協和化学工業：共同研究
    研究期間 : 2017年04月 -2019年03月 
    代表者 : 当真 要
  • レンコン浅床栽培方法の改良と連行栽培への「竹宝」施用効果の評価に関する研究、並びに生竹宝と茶殻の組み合わせによる園芸培土作成に関する研究
    長崎工業株式会社：共同研究
    研究期間 : 2015年04月 -2016年03月 
    代表者 : 当真 要
  • 文部科学省：科学研究費補助金(若手研究(B))
    研究期間 : 2013年 -2015年 
    代表者 : 当真 要
     
    愛媛大学農学部附属農場において、水田からのCH4およびN2O発生に与えるBiochar（竹炭）の施用効果を圃場条件下で調査した。2012年11月にBiochar（2000kg/ha）の施用の有無で2処理区を3反復で設け、2013年5月にそれら2処理区それぞれに化学肥料と有機肥料施用の２処理区を設置し計4処理区とした。CH4及びN2O発生量の調査はクローズドチャンバー法を用いて2012年11月以降10日～2週間に一回の頻度で行った。収穫時に坪刈りを行い整玄米収量を調査した。年間のCH4発生量は化学肥料区で261kgC/ha、有機肥料区で241kgC/ha、Biochar+化学肥料区で254kgC/ha、Biochar+有機肥料区で262kgC/haとなり、処理区間に有意な差は見られなかった。年間のN2O発生量は化学肥料区で-0.10kgN/ha、有機肥料区で0.28kgN/ha、Biochar+化学肥料区で-0.22kgN/ha、Biochar+有機肥料区で0.15kgN/haとなり、有機肥料の施用で有意にN2O発生量が増加していた（P<0.05）。一方で化学肥料区および有機肥料区へのBiochar施用で平均0.12kgN/haのN2O発生量が減少していた。畑土壌ではBiocharの施用がN2O発生量を減少する事象が知られており、水田でもBiocha施用でN2O発生量の可能性がある。整玄米収量は化学肥料区で468kg/10a、有機肥料区で424kg/10a、Biochar+化学肥料区で477kg/10a、Biochar+有機肥料区で408kg/10aとなり、有機肥料区で有意に整玄米収量が低下した（P<0.05）。水田へのBiocharの施用は玄米収量を維持しつつ、Biochar炭素の投入とN2O発生量の減少が期待でき、水稲栽培が地球温暖化に与える影響を緩和できる可能性がある。

産業財産権

  • 特許6327492:竹材及び茶殻の堆肥化方法    2018年04月27日
    当真要, 上野秀人, 森田展樹, 長崎信行

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