Foliar Feeding Rice with Nanoscale Selenium Slashes Fertilizer Waste and Boosts Nutrition
The cultivation of rice — the staple grain for more than 3.5 billion people around the world — comes with extremely high environmental, climate and economic costs. But scientists at the University of Massachusetts Amherst and China’s Jiangnan University have shown that nanoscale applications of the element selenium can decrease the amount of fertilizer necessary for rice cultivation while sustaining yields, boosting nutrition, enhancing the soil’s microbial diversity and cutting greenhouse gas emissions. In a new paper published in the Proceedings of the National Academy of Sciences, they demonstrate for the first time that such nanoscale applications work in real-world conditions.
Most crops only use about 40-60 percent of the nitrogen applied to them, and the nitrogen use efficiency of rice can be as low as 30 percent — meaning that 70 percent of what a farmer puts on their fields is wasted, washed away into streams, lakes and oceans, causing eutrophication, dead zones and a host of other environmental problems. Furthermore, when nitrogen is applied to soils, it interacts with the soil’s incredibly complex chemistry and microbes and ultimately leads to vastly increased amounts of methane, ammonia and nitrous oxide.
The researchers discovered that nanoscale selenium, an element crucial for plant and human health, when applied to the foliage and stems of the rice, reduced the negative environmental impacts of nitrogen fertilization by 41 percent and increased the economic benefits by 38.2 percent per ton of rice, relative to conventional practices.
Selenium stimulates the plant’s photosynthesis, which increased by more than 40 percent in the trials. Increased photosynthesis means the plant absorbs more CO2, which it then turns into carbohydrates. Those carbohydrates flow down into the plant’s roots, which causes them to grow. Bigger, healthier roots release a host of organic compounds that cultivate beneficial microbes in the soil, and it’s these microbes that then work symbiotically with the rice roots to pull more nitrogen and ammonium out of the soil and into the plant, increasing its nitrogen use efficiency from 30 to 48.3 percent and decreasing the amount of nitrous oxide and ammonia release to the atmosphere by 18.8-45.6 percent.
With more nutrients coming in, the rice itself produces a higher yield, with a more nutritious grain — levels of protein, certain critical amino acids, and selenium jumped. On top of this, nano-selenium applications allowed farmers to reduce their nitrogen applications by 30 percent.
Manchurian Walnut Could Hold Key to Eco-Friendly Weed Control
In the search for eco-friendly alternatives to synthetic herbicides, researchers from Kyushu University in Japan have identified a potent weed-inhibiting compound in the leaves of the Manchurian walnut tree. The discovery of the compound, 2Z-decaprenol, and its unique mode of action on plants could lead to the development of more sustainable herbicides. The study was published in the Journal of Agricultural and Food Chemistry.
Inspired by a professor who noticed areas with limited vegetation underneath local walnut trees, the researchers began to investigate allelopathy, the phenomenon in which plants release certain chemicals to suppress competitors.
In Japan, one naturally abundant and allelopathic tree is the Manchurian walnut, making it a promising candidate as a source for an eco-friendly herbicide. For many species in the walnut genus (Juglans), a chemical called juglone has been widely recognized as the primary allelochemical, but whether this chemical was responsible for the Manchurian walnut’s allelopathic effects was not yet known.
To investigate this, the researchers developed a soil-based bioassay designed to simulate the natural process of a leaf falling onto the ground and releasing its chemical contents into the soil. In their model, a filter paper treated with leaf extracts was placed on top of a soil layer, mimicking a fallen leaf. They then embarked on a process called bioassay-guided fractionation, which involved separating the crude extract from the walnut leaves into distinct chemical groups and repeatedly testing each group’s ability to inhibit the growth of tobacco seedlings, a plant chosen for its reliable germination rate.
The team observed that the most potent chemical group — the nonpolar n-hexane fraction — did not contain juglone, while the chloroform fraction that contained juglone showed a smaller inhibitory effect on tobacco seedling growth. Moreover, testing juglone alone based on its natural concentration in the leaves did not impact the tobacco seedling’s weight. This suggested to the research team that an alternative, more potent compound was responsible for the Manchurian walnut’s allelopathic effects.
After six successive rounds of purification and testing, the team isolated the single compound responsible for the most potent activity, 2Z-decaprenol. When tested, 2Z-decaprenol significantly inhibited the growth of the tobacco seedlings, causing reduced weight and a distinctive curling of the roots from the filter paper.
To see how 2Z-decaprenol operates at the molecular level, the team analyzed the genetic activity in the model plant Arabidopsis thaliana after treatment. They discovered that 2Z-decaprenol forced the plant to activate some defenses, such as producing protective chemicals and reinforcing its physical structure. At the same time, though, the compound crippled other essential pathways the plant needs to manage stress and to mount an effective immune response, effectively stopping the plant from growing.
Although the discovery of 2Z-decaprenol’s growth-inhibiting mechanism opens a new avenue for bioherbicide development, the team emphasizes that their research is still at its foundational stage.
Cellulose-Based Seed Lubricant Can Replace Toxic Materials
It can be difficult to prevent seeds from jamming in modern seeders. To keep them flowing smoothly, farmers use solid lubricants that prevent the seeds from clumping up or sticking together. Unfortunately, commercially available lubricants make use of talc or microplastics and can pose threats to farmers, farmland and pollinators.
Now, researchers from North Carolina State University have developed a new class of nontoxic, biodegradable solid lubricants.
The new lubricant is derived from cellulose, a biodegradable, plant-based material. Specifically, the lubricant consists of millions of tiny fibers measuring 0.2-2 millimeters long and 10-40 microns across. The surface of these fibers is grafted with hydrophobic particles, which repel water. To the naked eye, the collection of engineered fibers resembles a powder.
When this powder is mixed with seeds, it reduces friction in two ways. First, the surface of the fibers is smoother than the surface of the seeds. As the fibers slip between the seeds, they reduce mechanical friction that occurs when seeds rub against each other. Second, the hydrophobic particles on the surface of the fibers repel adsorbed water on the surface of the seeds, making the fibers even more slippery. This allows seeds to travel through seeders without jamming or clustering.
In proof-of-concept testing and field trials with corn and soybean seed, the new lubricant performed at least five times better than the best commercial talc lubricants and 25 times better than microplastic lubricants. It also outperformed current commercial lubricants when planting smaller seeds like mustard or canola, which are greatly affected by high humidity. Even in 80 percent humidity conditions, the new cellulose-based lubricant worked beautifully.
There was an unexpected finding as well. “Most seeds used in crop agriculture are covered with a thin coat of nutrients and pesticides,” said researcher Udayashankara Jamadgni. “When planting with conventional lubricants, some of this coating is scraped off. Pieces of seed coating that are scraped off are released in the exhaust system from the planting machinery, creating a toxic cloud that poses risks for pollinators, birds and farmers. We were surprised to find that our cellulose-derived lubricant drastically reduces this problem — very little of the seed coating is scraped off.
The researchers were additionally able to filter out the cellulose-derived fibers in the lubricant from the vacuum system used in farming machinery to plant the seeds. Very little of the lubricant itself is released into the environment.
Biodegradable Microplastics Rewire Carbon Storage in Farm Fields
We often think of plastic pollution as a problem of oceans and seabirds. But beneath our feet, in the quiet dark of agricultural soils, a new kind of contamination is unfolding — one with profound implications for climate, crops and carbon.
A pioneering two-year field study has revealed that biodegradable microplastics, often hailed as eco-friendly alternatives to conventional plastics, are quietly reshaping the chemistry of farmland soils in unexpected and complex ways. Published in Carbon Research, the team investigated how polypropylene (PP) — a common conventional plastic — and polylactic acid (PLA) — a widely used biodegradable plastic — affect soil organic carbon (SOC) in real-world agricultural conditions. Both were added at realistic concentrations (0.2 percent w/w) to topsoil (0–20 cm), with an unamended plot serving as control.
While neither plastic changed the total amount of carbon stored, the story beneath the surface was dramatically different. Surprisingly PLA had the strongest impact on carbon composition. It reduced plant-derived lignin in the soil by 32 percent, meaning fewer stable carbon compounds from roots and crop residues were being preserved.
Why? Because PLA attracted a special group of microbes known as K-strategists — slow-growing, efficient decomposers that specialize in breaking down tough, carbon-rich materials like lignin.
“These microbes see PLA as a feast,” explained researcher Jie Zhou. “But in doing so, they also ramp up enzymes that degrade other stubborn carbon compounds, including those that help lock carbon away long-term.” Yet PLA also boosted microbial necromass — the dead remains of bacteria and fungi — by 35 percent, a key but often overlooked pathway for carbon storage. This boost came from increased microbial diversity (+5.3 percent) and more complex microbial networks (+11 percent), creating a richer, more resilient soil ecosystem. Even more striking: fungal necromass became the dominant player, contributing 24 percent to SOC under PLA, compared to just 11 percent with conventional PP. Fungi, it turns out, thrive on PLA and help glue soil particles into stable macroaggregates, physically protecting carbon from decomposition.
But there’s a catch. PLA is rich in carbon but poor in nitrogen — an imbalance that triggers microbial nitrogen limitation. To survive, soil microbes began breaking down their own kind — specifically bacterial necromass, which dropped by 19 percent. The evidence? A strong negative correlation between bacterial remains and enzymes that scavenge nitrogen from the soil. “In trying to adapt to PLA, microbes start cannibalizing their own biomass,” said researcher Davey Jones. “It’s a survival strategy, but it could undermine long-term soil fertility and carbon stability.”
Meanwhile, polypropylene (PP) told a different story. Rather than altering microbial behavior, it suppressed microbial growth through carbon deprivation and the leaching of toxic additives. This led to reduced synthesis of necromass overall, weakening one of soil’s main carbon storage engines. “PP doesn’t feed the soil — it starves it,” said Jones. “It’s like putting a blanket over a garden: nothing grows underneath.”
This study shows that even biodegradable plastics can disrupt the delicate balance of carbon storage, shifting it from plant-based to microbial-based forms, with uncertain long-term consequences. “We can’t assume ‘biodegradable’ means ‘benign’,” warned Zhou. “In soil, these materials interact with living systems in complex ways we’re only beginning to understand.”
