What is perennial rice and why is it making history?

It may have taken more than 9,000 years of cultivation, but annual paddy rice is now available as a long-lived perennial rice

A report in Nature Sustainability chronicles the agronomic, economic, and environmental benefits of perennial rice cultivation across China’s Yunnan Province. In fact, already, the retooled crop is changing the lives of more than 55,752 smallholder farmers in southern China and Uganda.

What does the advancement of perennial rice mean for farmers?

The advancement of perennial rice really is revolutionary – it means farmers can plant the crop just once and reap up to eight harvests without sacrificing yield. This is an important step change relative to “ratooning,” or cutting back annual rice to obtain a second weaker harvest.

Reap up to eight harvests without sacrificing yield

“Farmers are adopting the new perennial rice because it’s economically advantageous for them to do so. Farmers in China, like everywhere else, are getting older. Everyone’s going to the cities; young people are moving away. Planting rice is very labor intensive and costs a lot of money. By not having to plant twice a year, they save a lot of labor and time,” explains Erik Sacks, professor in the Department of Crop Sciences at the University of Illinois and co-author on the report.

Development of perennial rice

Back in 1999, Sacks and senior authors Fengyi Hu and Dayun Tao, in collaboration with the Yunnan Academy of Agricultural Sciences and the International Rice Research Institute, began working on the development of perennial rice.

In subsequent years, the project grew to include the University of Illinois, Yunnan University, and the University of Queensland. Along the way, another partner, The Land Institute, joined the mission and provided highly sought-after perennial grain breeding and agroecology expertise and seed funding to ensure the project’s continued progress.

Perennial rice was developed through hybridization, by crossing an Asian domesticated annual rice with a wild perennial rice from Africa. Taking advantage of modern genetic tools to fast-track the process, the team identified a promising hybrid in 2007, planted large-scale field experiments in 2016, and released the first commercial perennial rice variety, PR23, in 2018.

The international research team spent five years studying perennial rice performance alongside annual rice on farms throughout Yunnan Province. With few exceptions, over the first four years, perennial rice yield [6.8 megagrams per hectare] was equivalent to annual rice [6.7 megagrams per hectare].

In the fifth year, the yield began to drop due to various reasons. It led the experts to recommend re-sowing perennial rice after four years.

Reduction of time, labor and fertilizer

Because perennial rice does not have to be re-planted every season, researchers found that farmers growing perennial rice put in almost 60% less labor and saved nearly half on the money spent on seed, fertilizer, and other inputs.

“The reduction in labor, often done by women and children, can be accomplished without substitution by fossil fuel–based equipment, an important consideration as society aims to improve livelihoods while reducing greenhouse gas emissions associated with agricultural production,” Sacks comments.

Profits of perennial rice ranged from 17% to 161% above annual rice

Naturally, the economic benefits of perennial rice varied across study locations, but profits ranged from 17% to 161% above annual rice. Even in sites and years when perennial rice suffered temporary yield dips due to pests, farmers still achieved a greater economic return than by growing the annual crop.

“That first season, when they planted the annual and the perennial rice side by side, everything was the same, essentially. Yield is the same, costs are the same, there’s no advantage,” Sacks added.

“But the second crop and every subsequent crop comes at a huge discount, because you don’t have to buy seeds, you don’t have to buy as much fertilizer, you don’t need as much water, and you don’t need to transplant that rice. It’s a big advantage.”

The research team documented the main environmental benefits

• Avoids twice-yearly tillage
• Higher soil organic carbon and nitrogen stored in soils under perennial rice
• Additional soil quality parameters improved

“Modern high-yielding annual crops typically require complete removal of existing vegetation to establish and often demand major inputs of energy, pesticides, and fertilizers. This combination of repeated soil disturbance and high inputs can disrupt essential ecosystem services in unsustainable ways, especially for marginal lands,” says Hu, professor and dean in the School of Agriculture at Yunnan University.

“Perennial rice not only benefits farmers by improving labor efficiency and soil quality, but it also helps replenish ecological systems required to maintain productivity over the long term.”

Assessing the low-temperature tolerance of perennial rice

Another aspect of the study assessed the low-temperature tolerance of perennial rice. The goal of this section of the research project was to predict its optimal growing zone around the world. Although significant exposure to cold limited regrowth, the research team predicted that the crop could work in a broad range of frost-free locations.

Although the research team has already looked into on-farm testing and released three perennial rice varieties as commercial products in China and one in Uganda, the researchers are by no means finished refining the crop. They plan to use the same modern genetic tools to quickly introduce desirable traits such as aroma, disease resistance, and drought tolerance into the new crop, potentially expanding its global reach.

“While early findings on the environmental benefits of perennial rice are impressive and promising, more research and funding are needed to understand the full scope of perennial rice’s potential,” says Tim Crews, Chief Scientist at The Land Institute and study co-author.

“Questions about carbon sequestration and persistence and greenhouse gas balances in perennial paddy rice systems remain. Researchers must also make progress on perennializing upland rice, which could curb highly unsustainable soil erosion on farmlands across Southeast Asia. As the work of Dr. Hu’s group at Yunnan University progresses, The Land Institute and an ever-growing network of collaborators will continue to support these research and scaling efforts for perennial rice globally.”

Sacks concludes: “I think now, with perennial rice in farmers’ fields, we have turned a corner. We have been feeding humanity by growing these grains as annuals since the dawn of agriculture, but it wasn’t necessarily the better way. Now we can consciously choose to make a better crop, and a better, more sustainable agriculture. We can fix the errors of history.”

The article “Sustained productivity and agronomic potential of perennial rice” is published in Nature Sustainability.