Nav: Home

Reining in soil's nitrogen chemistry

July 11, 2018

Take a trip down into the soil beneath a field of crops. You won't find just dirt, water, and creepy-crawlies. You'll also find reactions that remind you of high school chemistry lab.

Many researchers study the reactions of elements and compounds in the soil, especially because some, like nitrogen, are required by plants to grow. Nitrogen is often added to the soil as a fertilizer. However, not all nitrogen added is usable by plants.

The compound urea is currently the most popular nitrogen soil fertilizer. It's a way to get plants the nitrogen they need to grow. Although the nitrogen in urea is not directly usable by plants, once urea is in the soil it undergoes a chemical reaction that produces ammonium, a nitrogen-rich compound that thus becomes available for plant nutrition. The catalyst responsible for this reaction is an enzyme called urease. This enzyme is produced by microorganisms in the soil.

There's just one problem with urease: it works too well!

"The reactions that urea undergoes are much too fast, because of the action of urease," says Stefano Ciurli. Ciurli is a professor of chemistry at the Department of Pharmacy and Biotechnology of the University of Bologna, Italy. "Urease accelerates the formation of nitrogen-containing compounds that quickly dissipate into the environment instead of being absorbed by plants."

Controlling how fast the urease accelerates the process is important to help plants get as much nitrogen as possible. This is usually done by modifying the urea fertilizer to decrease urease activity. Ciurli and his team study these techniques. They looked to prove if coating the urea fertilizer granules with a specific compound--maleic-itaconic polymers (MIPs)--would help with this. Previous studies had argued that it didn't have an effect.

What they found was that, at some levels of soil acidity, their compound was good at slowing down urease. They found that their compound compared well to another used for this purpose, N-(n-butyl)-thiophosphoric triamide (NBPT). However, this second compound has been shown to have some negative effects on crops in addition to being incorporated in plants and soil organisms.

The research results suggest farmers may have a choice, depending on their soil's acidity.

"For farmers who already use the compound we tested, this study tells them why the chemical is effective," Ciurli says. "Those that have been discouraged from using it because they didn't think it worked can now explore the benefits of it compared to other chemicals available in the market."

What prevents the plants from being able to take up the urea in the first place? What makes a nutrient unavailable to the plant?

"Plants can only absorb nutrients through their roots if the chemical is soluble in the water contained in soil," Ciurli explains. "Plants don't have teeth to chew on soil; they only have roots that can almost passively absorb what 'comes by' them."

In the soil, there can be many forms of nitrogen. Some are gases and are easily lost into the air. Others in the soil can be "sticky" or not sticky. Those that are not sticky, such as nitrates, are easily taken up by plants but also easily washed away from the soil into rivers and lakes. Their abundance there can lead to algal blooms and dead zones.

Ciurli says one of the next steps in their research is carrying out similar studies in the soil, as this study was done in the laboratory.

The work has implications for plants as well as Ciurli's other passion, pharmaceuticals for metal-based biological targets.

"The knowledge of how urease works, at the molecular/atomic level, is a first step to develop urease inhibitors for both agricultural application and also for medical issues," he says. "Urease is the key virulence factor for a series of microorganisms that cause antibiotic resistance, cancer, tuberculosis, plague, and brain diseases. Knowing the chemistry of this enzyme will contribute to the battle of the human race for its survival on this planet."
-end-
Read more about this research in the Soil Science Society of America Journal.

American Society of Agronomy

Related Nitrogen Articles:

We must wake up to devastating impact of nitrogen, say scientists
More than 150 top international scientists are calling on the world to take urgent action on nitrogen pollution, to tackle the widespread harm it is causing to humans, wildlife and the planet.
How nitrogen-fixing bacteria sense iron
New research reveals how nitrogen-fixing bacteria sense iron - an essential but deadly micronutrient.
Corals take control of nitrogen recycling
Corals use sugar from their symbiotic algal partners to control them by recycling nitrogen from their own ammonium waste.
Foraging for nitrogen
As sessile organisms, plants rely on their ability to adapt the development and growth of their roots in response to changing nutrient conditions.
Inert nitrogen forced to react with itself
Direct coupling of two molecules of nitrogen: chemists from Würzburg and Frankfurt have achieved what was thought to be impossible.
Researchers discover new nitrogen source in Arctic
Scientists have revealed that the partnership between an alga and bacteria is making the essential element nitrogen newly available in the Arctic Ocean.
Scientists reveal impacts of anthropogenic nitrogen discharge on nitrogen transport in global rivers
Scientists found that riverine dissolved inorganic nitrogen in the USA has increased primarily due to the use of nitrogen fertilizers.
Nitrogen gets in the fast lane for chemical synthesis
A new one-step method discovered by synthetic organic chemists at Rice University allows nitrogen atoms to be added to precursor compounds used in the design and manufacture of drugs, pesticides, fertilizers and other products.
Nitrogen fixation in ambient conditions
EPFL scientists have developed a uranium-based complex that allows nitrogen fixation reactions to take place in ambient conditions.
New regulators of nitrogen use in plants identified
Researchers have identified a set of gene regulators in plants that could help plants utilize nitrogen better, which would prevent ecological damage from excess nitrogen in the soil.
More Nitrogen News and Nitrogen Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab