New Biodegradable Beads May Help Crops Receive Nitrogen Naturally
Researchers at South Dakota State University are developing biodegradable hydrogel beads that may help crops receive nitrogen naturally.
The technology is inspired by Mexican corn and soybean plants. These plants create special environments where bacteria can fix nitrogen for plant use.
SDSU researchers Srinivas Janaswamy and Senthil Subramanian lead the study. Their research explores how hydrogel beads can protect nitrogen-fixing bacteria and help them remain active.
The study is published in Plant and Soil. It focuses on creating small environments similar to the low-oxygen conditions found inside natural root nodules.
Nitrogen is important for healthy plant growth. However, most plants cannot use nitrogen gas directly from the air.
Certain bacteria can convert nitrogen gas into forms that plants can use. This process is called biological nitrogen fixation.
The process depends on an enzyme called nitrogenase. However, nitrogenase is highly sensitive to oxygen.
Some Mexican corn varieties use a gel-like material around their aerial roots to support nitrogen-fixing bacteria. Soybeans use root nodules to create a similar environment.
The SDSU team used alginate, a biodegradable material made from seaweed, to create hydrogel beads. Researchers tested beads made with calcium, strontium, zinc, nickel, copper, and aluminum.
They also tested two nitrogen-fixing bacteria, Azospirillum brasilense and Herbaspirillum seropedicae.
Calcium beads showed the strongest results. They maintained low oxygen levels and captured more than 70% of the bacteria added to the beads.
The calcium beads also helped the bacteria survive longer. Bacteria inside the beads showed nitrogenase activity similar to bacteria grown under ideal laboratory conditions.
“One of the biggest challenges in using free-living nitrogen-fixing bacteria in agriculture is protecting the nitrogenase enzyme from oxygen while still allowing the microbes to remain active," Subramanian said.
Researchers also tested glucose as an energy source. Glucose increases nitrogenase activity in Herbaspirillum seropedicae but decreases activity in Azospirillum brasilense.
The results showed that different bacteria can respond differently to the same energy source.
The hydrogel beads gradually broke down in soil over approximately 120 days. This could make the technology useful for sustainable farming.
“Nature already provides examples of microorganisms fixing nitrogen efficiently when they live in the right microenvironment, "Janaswamy said. "Our research demonstrates that biodegradable hydrogels can recreate these conditions, supporting biological nitrogen fixation by maintaining the environment required for the nitrogenase enzyme to remain active".
Photo Credit: South Dakota State University