Elucidation of crop production improvement on changes of soil microorganisms by adsorption of substances exuding from roots to biochar

• Project/Area Number: 17K07623
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Crop production science
• Research Institution: Tottori University
• Principal Investigator: NISHIHARA Eiji 鳥取大学, 農学部, 教授 (40452544)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2017: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
• Keywords: アレロケミカル / 炭化物（活性炭） / 物質吸着 / 根粒菌 / 温室効果ガス（N2O) / 炭化物特性 / 活性炭 / 連作障害回避 / 硝化菌

Outline of Final Research Achievements

Activated carbon (AC) is a known adsorbent for organic compounds including root exudates but could have an influence on crop yield, microorganisms and greenhouse gas (GHG) emissions. A 2-year pot experiment was conducted to assess the effect of AC on GHG emissions, seed yield, root exudates, and nodulation after harvest. The soybean genotypes used were TnVRSN4, Tachinagaha and TnVRNN4 with very high, normal and very low nodulation capacities respectively under different rates of AC (0, 2.4, 4.8 and 9.6 t・ha－1) with inorganic fertilizer.
The results showed that AC tended to reduce N2O emissions in TnVRSN4 soils in both years due to the significant reduction in nodulation. AC did not significantly affect seed yield of TnVRSN4 but significantly reduced seed yield of TnVRNN4 and Tachinagaha in 2017 and 2018 respectively.
Root isoflavone were not significantly affected by AC but significantly reduced the concentration of daidzein and daidzin in soil.

Academic Significance and Societal Importance of the Research Achievements

本研究は、連作障害を回避させる資材である活性炭施用によってマメ科ダイズの子実収量、マメ科に着生する根粒菌、そして化学肥料と収穫後の根粒菌の腐敗から発生する温室効果ガスの一種であるN2Oの発生の影響を調査した。一般にダイズのようなマメ科作物は根粒菌の着生のため、窒素肥料の施用量は少ないとされている。しかし、本研究によって、AC施用は、ダイズから滲出する根粒菌着生の誘導物質を吸着させ根粒菌の着生量が減少させながら、子実収量を維持させることを証明した。さらにAC施用によって根粒菌着生数が減少し、収穫後の根粒菌の腐敗から発生するN2Oもほぼなくなる環境にやさしい栽培になることを明らかにした。

Research Products

• [Journal Article] Effect of activated carbon on greenhouse gas emissions, seed yield, soil chemical properties and isoflavone content of soybean genotypes with varying nodulation capacities under sandy soil conditions (2020)
  • Author(s): Daniel Basalirwa, Shigeto Sudo, Cosmas Wacal, Caroline Namirembe, Daisuke Sasagawa, Sadahiro Yamamoto, Tsugiyuki Masunaga, Eiji Nishihara
  • Journal Title: Rhizosphere Volume: 14 Pages: 100202-100202
  • Peer Reviewed
• [Presentation] Effect of activated carbon on yield and greenhouse gas emission in relation to isoflavones from different soybean (Glycine max (L.) Merr.) lines in sandy soil. (2018)
  • Author(s): Daniel Basalirwa, Shigeto Sudo, Fuyumi Akae, Cosmas Wacal, Aung Zaw Oo, Daisuke Sasagawa, Sho Koyama, Robert Acidri, Tadashi Ishigaki, Takuo Handa, Eiji Nishihara
  • Organizer: 日本土壌肥料学会2018年度神奈川大会
• [Presentation] Seed isoflavone, protein content and yield of soybean (Glycine max (L.) Merr.) lines grown in sandy soils amended with activated carbon (2018)
  • Author(s): Daniel Basalirwa, Daisuke Sasagawa, Cosmas Wacal, Robert Acidri, Naohiro Yamada, Eiji Nishihara
  • Organizer: 日本作物学会246回講演会