Grains that grow year after year without having to be replanted could save money, help the environment, and reduce the need for back-breaking labor. Now, the largest real-world test of such a crop—a perennial rice grown in China—is showing promise. Perennial rice can yield harvests as plentiful as the conventional, annually planted crop while benefiting the soil and saving smallholder farmers considerable labor and expense, researchers have found…

All rice is perennial to some extent. Unlike wheat or corn, rice roots sprout new stems after harvest. The trouble is that this second growth doesn’t yield much grain, which is why farmers plow up the paddies and plant new seedlings. The improved perennial rice, in contrast, grows back vigorously for a second harvest. Researchers developed it by crossing an Asian variety of rice with a wild, perennial relative from Nigeria. Improving the offspring took decades, and in 2018 a variety called Perennial Rice 23 (PR23) became commercially available to Chinese farmers. This was a “scientific breakthrough,” says Koichi Futakuchi, a crop scientist at the Africa Rice Center…

Over 4 years PR23 averaged 6.8 tons of rice per hectare, slightly higher than the annual rice, they report today in Nature Sustainability. As hoped, the perennial crop tended to grow back again and again without sacrificing the size of the harvest. In the fifth year, however, the yields of PR23 declined for some reason, suggesting it needed to be replanted. The perennial rice also improved the soil.

Researchers note potential risks. Because PR23 enables farmers to till less, fungi and other pathogens can build up in the fields. Insects can persist in the stubble after harvest, because it’s not plowed under, then transmit viruses when they feed on the regenerating sprouts in the spring. And without tilling, weeds can flourish; the researchers found that fields with PR23 needed one to two more herbicide treatments than regular rice. They also note that it’s more work to resow the perennial rice when its yield falters, because its larger and deeper roots need to be killed.

Excerpts from ‘Perennial’ rice saves time and money, but comes with risks, Science, Nov. 7, 2022