Beneficial Root Microbes Boost Rice Yields Without Fertilizers, Study Finds

Despite being the staple food for more than half of the world's population, rice cultivation remains highly resource-intensive, requiring substantial amounts of water and chemical fertilizers. However, as environmental concerns about global food security and climate change grow, there is increasing interest in exploring more sustainable methods for growing this crucial crop. One promising avenue involves harnessing the power of beneficial root microbes. In a study published in Plant and Cell Physiology, researchers from the Nara Institute of Science and Technology (NAIST) in Japan have delved into how naturally occurring root microbes in rice can support plant growth, potentially reducing the dependency on synthetic fertilizers. The team, led by Professor Yusuke Saijo, examined rice plants (Oryza sativa ssp. japonica) grown in an experimental field that has been healthy and productive for over 70 years without the use of fertilizers or pesticides. They compared the root microbiomes from this unfertilized field with those from a nearby conventionally fertilized field. Using 16S rRNA gene sequencing, the researchers analyzed microbial DNA in the roots of three Japanese rice cultivars—Nipponbare, Hinohikari, and Kinmaze. They collected samples every two to three weeks throughout the growing season, spanning one to four years. Their findings indicated that microbial diversity in the rice roots increased as the plants matured. In particular, the roots of high-yielding, unfertilized rice were enriched with nitrogen-fixing bacteria, which can convert atmospheric nitrogen into a form usable by plants, thereby compensating for the lack of added fertilizers. The study also revealed that the microbial community in the rice roots changed significantly over time. During the early vegetative stage, anaerobic bacteria were more dominant, while aerobic and microaerophilic bacteria became more prevalent during the reproductive and maturation stages. This shift likely reflects the common practice of draining water from rice paddies during certain developmental periods, which changes the oxygen levels in the soil. These insights into the assembly and function of beneficial microbes in rice roots grown in nutrient-poor soils open up exciting possibilities for sustainable agriculture. Professor Yusuke Saijo commented, "Looking ahead, isolating these beneficial bacteria and utilizing them in customized microbial blends could pave the way for sustainable rice farming." The research team, comprising experts from multiple institutions, included Saijo, Asahi Adachi, John Jewish Dominguez, Masako Fuji, Yuniar Devi Utami, Sumire Kirita, Shunsuke Imai, Naoaki Ono, and Shigehiko Kanaya from NAIST, Takehiro Kamiya and Toru Fujiwara from the University of Tokyo, Takumi Murakami and Yuichi Hongoh from the Tokyo Institute of Technology, Rina Shinjo from Nagoya University, and Kiwamu Minamisawa from Tohoku University, all in Japan. This research underscores the potential of microbial solutions to enhance rice yields in unfertilized fields, offering a path toward more environmentally friendly and resource-efficient farming practices.