Unveiling the microbial mechanisms behind 'rice gorws on soil fertility' and their application toward realization of a low-carbon society
As the traditional concept 'rice grows on soil fertility' suggests, rice production is greatly supported by the nitrogen fertility of paddy soils.
As a mechanism for sustaining soil nitrogen fertility, the nitrogen fixation reaction by soil microorganisms (incorporating nitrogen gas from the atmosphere into microbial biomass) is important.
Recently, using metatranscriptomic analysis, we discovered that 'iron-reducing bacteria' abundant in paddy soils might be key players in nitrogen fixation.
We successfully isolated iron-reducing bacteria from paddy soils and revealed that they utilize carbon compounds derived from rice straw as nutrients, utilize ferric iron oxides for anaerobic respiration, and perform nitrogen fixation.
This 'nitrogen fixation by iron-reducing bacteria' might be the core mechanism for sustainable nitrogen fertility in paddy soils, and we are now advancing various investigations to elucidate its scientific basis.
In field trials, we demonstrated that applying rice straw and ferric iron oxides to paddy soils enhanced soil nitrogen fixing activity and maintained rice yields even with reduced nitrogen fertilization.
This 'fertilizing soil with iron' technology is expected to be applied to low-nitrogen agriculture, which reduces nitrogen fertilizer input and alleviates nitrogen burdens on the environment.
Furthermore, it contributes to reducing carbon dioxide emissions from nitrogen fertilizer production and to mitigating methane emissions from paddy soils, thereby supporting the realization of a low-carbon society.
Educational approach
Clarifying the soil biological functions for sustainable agriculture and ecosystem conservation
Mission of the Laboratory of Soil Microbial Functions is clarifying the soil biological functions for sustainable agriculture and ecosystem conservation. We conduct research and educational activities in collaboration with the Labpratpry of Soil Science (Department of Applied Biological Chemistry).
Soil forms the foundation of terrestrial ecosystems and supports crop production.
There, the enormous number of diverse microorganisms inhabiting the soil make great contributions.
Clarifying and utilizing the soil biological functions is an important challenge to keep soil health and to sustain humanity's survival.
In research, we aim for studies that lead the world, move history, and pioneer the academic community.
In education, we hope students will grow into active researchers worldwide, acquire diverse skills through research, and develop into human resources who thrive in society.
We hope students to gain the sense of achievement, confidence, and inspiration that only those who devote themselves fully to research can obtain.
Vision for industry-academia collaboration
Contributing to the realization of a low-carbon society with the 'fertilizing soil with iron' technology
Modern crop production is supported by large amount of nitrogen fertilizers.
Over the past 50 years, global nitrogen fertilizer consumption has increased more than tenfold.
The production, transport, and application of fertilizers rely on fossil energy, leading to carbon dioxide emissions.
Moreover,large amount of nitrogen fertilization in cropland causes the greenhouse gas N2O (nitrous oxide) emission from soils and nitrate leaching, polluting aquatic systems.
Therefore, the development of crop production technologies that minimize nitrogen fertilizer use while maintaining maximum productivity (low-nitrogen agriculture) has become a critical global issue.
Recently, we discovered the 'nitrogen fixation by iron-reducing bacteria ', the core mechanism supporting the sustainable nitrogen fertility of paddy soils, using metatranscriptomic analysis.
Iron-reducing bacteria in paddy soils utilize carbon compounds derived from rice straw as nutrients, reduce iron oxides by anaerobic respiration, and perform nitrogen fixation.
We are currently elucidating the academic basis of this newly discovered ' nitrogen fixation by iron-reducing bacteria' from the viewpoints of soil science and microbial ecology.
At the same time, we are advancing applied research aimed at establishing low-nitrogen agriculture by utilizing this process.
Field trials showed that applying rice straw and ferric iron oxides to paddy soils enhanced nitrogen fixation by iron-reducing bacteria and enabled rice production with reduced nitrogen fertilizer.
It was also shown that the application of iron reduced methane emissions from paddy soils.
This 'fertilizing soil with iron' technology reduces nitrogen-related environmental pollution and mitigates greenhouse gas emissions, thereby contributing to the realization of a low-carbon society.
We aim to accelerate the development and social implementation of this technology.
