Farmers adopt high-yielding, cost-saving perennial rice
After more than 9,000 years in cultivation, annual paddy rice is now available as a long-lived perennial. The advancement means farmers can plant just once and reap up to eight harvests without sacrificing yield — better even than “ratooning,” the practice of cutting back annual rice to obtain a second, weaker harvest.
A new report in Nature Sustainability chronicles the agronomic, economic, and environmental outcomes of perennial rice cultivation across China’s Yunnan Province.
“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,” says Erik Sacks, professor in the Department of Crop Sciences at the University of Illinois and co-author on the report.
Sacks began working to develop perennial rice in 1999 in a collaboration with several universities. Another partner, The Land Institute, provided perennial grain breeding and agroecology expertise, along with seed funding to ensure continuity of the project.
The researchers developed perennial rice through hybridization, 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, perennial rice yield (6.8 megagrams per hectare) was equivalent to annual rice (6.7 megagrams per hectare) over the first four years. Yield began to drop off in the fifth year due to various factors, leading the researchers to recommend re-sowing perennial rice after four years.
But because they didn’t have to plant each season, farmers growing perennial rice put in almost 60 percent less labor and spent nearly half as much on seed, fertilizer and other inputs.
The economic benefits of perennial rice varied across study locations, but profits ranged from 17 to 161 percent 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 says. “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.”
Avoiding twice-yearly tillage, perennial rice cultivation also provides significant environmental benefits. The research team documented higher soil organic carbon and nitrogen stored in soils under perennial rice. Other soil quality parameters improved as well.
Another piece of the study assessed the low-temperature tolerance of perennial rice, with the goal of predicting its optimal growing zone around the world. Although significant exposure to cold limited regrowth, the research team predicts the crop could work in a broad range of frost-free locations.
Although they’ve already conducted on-farm testing and released three perennial rice varieties as commercial products in China and one in Uganda, the researchers aren’t done 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 reach across the globe.
How Plants Steer Clear of Salt
Whereas a bath in the ultra-salty Dead Sea may be a balm for human soul and body, the relationship between most plants and salt is quite the opposite. Plants desperately do whatever they can to steer clear of salinity, as salts can damage and even suffocate them.
Unfortunately, salt in agricultural land is an accelerating global problem, partly due to climate change, which increases the salinity of soil whenever floods sweep coastal zones. Typically, this lowers crop yields.
To avoid salt in soil, plants can change their root direction and grow away from saline areas. University of Copenhagen researchers have recently found out what makes this possible. The discovery changes our understanding of how plants change their shape and direction of growth and may help alleviate the accelerating global problem of high soil salinity on farmland. The results were published in the journal Developmental Cell.
The research group discovered that when a plant senses local concentrations of salt, the stress hormone ABA (abscisic acid) is activated in the plant. This hormone then sets a response mechanism into motion.
“The plant has a stress hormone triggered by salt. This hormone causes a reorganization of the tiny protein-based tubes in the cell, called the cytoskeleton. The reorganization then causes the cellulose fibers surrounding the root cells to make a similar rearrangement, forcing the root to twist in such a way that it grows away from the salt,” explains Professor Staffan Persson of the University of Copenhagen’s Department of Plant and Environmental Sciences.
The leading role played by the stress hormone is what makes the discovery a surprise for the researchers. Until now, it was believed that the hormone auxin controlled a plant’s ability to change directions in response to various environmental influences (known as tropisms).
“That the stress hormone ABA is crucial for plants being able to reorganize their cell walls and change shape and direction of growth is completely new. This could open new avenues in plant research, where there will be a greater focus on the significant role that the hormone seems to play in the ability of plants to cope with various conditions by changing movement,” says Persson.
By mutating a single amino acid in a protein that drives the twisting of the root, the researchers were able to reverse the twist so that the plant could not grow away from the salt.
Persson believes that it will be some time before the new knowledge is applied in agriculture — not least because GMOs remain banned in the EU. However, the results may open the way for the development of more salt-tolerant crop varieties.
“Plants produce more of the stress hormone when they sense salt. It’s not hard to imagine that if you can speed up a plant’s stress response by changing other aspects of the cytoskeleton, you can probably make its root-twist happen faster. In this way, we can strengthen plants by reducing their exposure to salt,” says Professor Persson.
‘Forever Chemicals’ Persist through Wastewater Treatment, May Enter Crops
PFAS (per-and polyfluoroalkyl substances), a group of more than 4,700 fully synthetic compounds that are widely used in industrial and manufacturing processes and found in many consumer products, persist through wastewater treatment at levels that may impact the long-term feasibility of “beneficial reuse of treated wastewater,” according to a study conducted by researchers at Penn State and recently published in the Agronomy Journal.
PFAS, often referred to as “forever chemicals,” are used to make fluoropolymer coatings and products that resist heat, oil, stains, grease and water, and are found in a variety of products, from clothing and furniture to food packaging and non-stick cooking surfaces.
“PFAS are so pervasive and persistent that they have been found in the environment all over the world, even in remote locations,” said Heather Preisendanz, associate professor of agricultural and biological engineering at Penn State. “Unfortunately, these compounds have been shown to negatively impact ecological and human health, particularly because they can bioaccumulate up the food chain and affect development in children, increase risk of cancer, contribute to elevated cholesterol levels, interfere with women’s fertility and weaken immune systems.”
Because of their wide variety of uses, PFAS enter wastewater treatment plants from both household and industrial sources, said Preisendanz.
Beneficial reuse of treated wastewater is an increasingly common practice in which treated wastewater is used for irrigation and other non-potable purposes. According to Preisendanz, this practice provides an opportunity for the soil to act as an additional filter for PFAS, reducing the immediate impact of direct discharge of PFAS to surface water, as would typically happen following traditional wastewater treatment. However, given that the chemical structures of PFAS are difficult to degrade, the risks and potential tradeoffs of using treated wastewater for irrigation practices, especially in the long-term, are not well understood.
“PFAS have been shown to be taken up by crops and enter the food chain when the crops are consumed, so when treated wastewater is used for irrigation activities in agricultural fields, understanding these tradeoffs is of critical importance,” she said.
Preisendanz and her colleagues analyzed PFAS concentrations in water that passed through a water reclamation facility. They collected bi-monthly water samples from fall 2019 through winter 2021 prior to treatment and after treatment. Since the treated water from the wastewater treatment plant is used to irrigate nearby crops, the team also collected tissues from those crop plants, including corn silage and tall fescue, to assess for the presence of PFAS.
The team identified 10 types of PFAS across the site, with average total measured concentrations of 88 ng/L (nanograms per liter) in the wastewater effluent and concentrations as high as 155 ng/L in the downstream monitoring wells. The conclusions suggest that occurrence of PFAS across the site is nearly ubiquitous and that levels increase with the direction of groundwater flow.
“The United States Environmental Protection Agency recently released updated health advisories for two of the most important PFAS — PFOA (Perfluorooctanoic acid) and PFOS (Perfluorooctanesulfonic acid) — such that ‘any detectable level is considered a risk to human health,’” said Preisendanz. “This presents potential challenges for beneficial reuse of wastewater.”
While the groundwater near the spray-irrigation site the team studied is not used for drinking, and not likely to pose a risk to human health in that regard, the team did find several PFAS compounds in crop tissue samples collected at both irrigated and non-irrigated portions of the site.
“This suggests that PFAS may enter the food chain when these crops are fed to livestock,” Preisendanz said, adding that future research is needed to determine potential risks to livestock health and the potential implications of PFAS presence in meat and dairy products, including milk.
UV-to-Red Light-Converting Films Accelerate Plant Growth
An interdisciplinary team from Hokkaido University’s Engineering and Agriculture departments and the Institute for Chemical Reaction Design and Discovery (WPI-ICReDD) has developed a europium-based thin-film coating that accelerates both vegetal plant and tree growth. This technology can improve plant production speed and has the potential to help address global food supply issues.
Plants convert visible light to energy via photosynthesis, but in addition to visible light, sunlight also contains ultraviolet (UV) light. Researchers in this study aimed to provide plants with additional visible light to use in photosynthesis by employing a wavelength-converting material (WCM) that can convert the UV light into red light.
Researchers developed a WCM based on a europium complex (Eu3+) and made a thin-film coating that can be applied to commercially available plastic sheets. Researchers not only showed that the film converts UV light to red light, but also that the film does not block any of the beneficial visible light from the sun. The film was then tested by comparing plant growth using sheets with and without the WCM coating.
Trials were performed for both Swiss chard, a vegetal plant, and Japanese larch trees. In summer, when days are long and sun irradiation is strong, no significant difference was observed for Swiss chard when using the WCM films. In winter, however, when days are shorter and sunlight is weaker, Swiss chard plants grown using the WCM films showed 1.2 times greater plant height and 1.4 times greater biomass after 63 days. Researchers attributed this accelerated growth to the increased supply of red light provided by the WCM films.
Trials involving Japanese larch trees also showed accelerated growth. Seedlings showed a higher relative growth rate in the initial four months of growth, resulting in a stem diameter 1.2-fold larger and total biomass 1.4-fold larger than trees grown without the WCM coating. Critically, this enabled the seedlings to reach the standard size for planting in the forestry of Hokkaido within one year. Use of WCM films could shorten the growth period of seedlings from two years to one, resulting in more cost-efficient plant production.
This technology also has the potential to help with food security issues in colder climates and is beneficial because it does not require any electricity to operate. Researchers see the customizability of the technology as especially promising — they believe they can design WCMs that will produce other colors of light that can be optimized for specific plant types.
Insects Contribute to Atmospheric Electricity
By measuring the electrical fields near swarming honeybees, researchers have discovered that insects can produce as much atmospheric electric charge as a thunderstorm cloud. This type of electricity helps shape weather events, aids insects in finding food, and lifts spiders up in the air to migrate over large distances. The research, which appeared in the journal iScience, demonstrates that living things can have an impact on atmospheric electricity.
“We always looked at how physics influenced biology, but at some point, we realized that biology might also be influencing physics,” says first author Ellard Hunting, a biologist at the University of Bristol. “We’re interested in how different organisms use the static electric fields that are virtually everywhere in the environment.”
As with most living creatures, bees carry an innate electric charge. Having found that honeybee hive swarms change the atmospheric electricity by 100 to 1,000 volts per meter, increasing the electric field force normally experienced at ground level, the team developed a model that can predict the influence of other species of insects.
“How insect swarms influence atmospheric electricity depends on their density and size,” says co-author Liam O’Reilly, a biologist at the University of Bristol. “We also calculated the influence of locusts on atmospheric electricity, as locusts swarm on biblical scales, sizing 460 square miles with 80 million locusts in less than a square mile; their influence is likely much greater than honeybees.”
“We only recently discovered that biology and static electric fields are intimately linked and that there are many unsuspected links that can exist over different spatial scales, ranging from microbes in the soil and plant-pollinator interactions to insect swarms and perhaps the global electric circuit,” says Ellard.
“Interdisciplinarity is valuable here — electric charge can seem like it lives solely in physics, but it is important to know how aware the whole natural world is of electricity in the atmosphere,” says co-author Giles Harrison, an atmospheric physicist from the University of Reading.
