The reason is not hard to find: According to the Intergovernmental Panel on Climate Change

According to the International Patent Cooperation Council (IPCC), between 16% and 27% of human-caused climate change emissions are related to agriculture.

However, most of these emissions are not the familiar carbon dioxide that is the culprit for global warming.

It’s another gas entirely: nitrous oxide (N2O).

N2O is what we know as "laughing gas," said NYU nutrient pollution researcher and International Nitrogen Initiative

(International Nitrogen Initiative, a group focused on nitrogen pollution research and policy making

David Kanter, vice president of the International Monetary Fund, believes that it is not getting the attention it deserves. He said:

“This greenhouse gas is often forgotten.” However, on a molecular basis, N2O plays a significant role in warming the atmosphere.

It is approximately 300 times more potent than carbon dioxide.

Like carbon dioxide, it has a long lifespan, remaining in the air for an average of 114 years before breaking down.

It also depletes the ozone layer. In short, the impact of nitrous oxide on the climate cannot be underestimated. IPCC scientists estimate that

N2O accounts for about 6% of greenhouse gas emissions, and about three-quarters of these N2O emissions come from agriculture.

Despite its important contribution to climate change, policymakers have yet to directly address N2O emissions.

N2O is still accumulating. A 2020 review of N2O sources and sinks found that over the past 40 years, N2O

Emissions increased by 30%, nearly exceeding the IPCC's highest possible emissions scenario. The culprit is agricultural land.

soils – especially because of the massive global use of synthetic nitrogen fertilizers.

Today, scientists are trying various methods of treating the soil or adjusting farming practices to reduce N2O production.

Mike, an agricultural ecologist and soil scientist at Iowa State University

“Anything that can improve fertilizer efficiency is going to be very important,” said Michael Castellano, an expert on fertilizer use.

It will be of great help.”

An imbalanced nitrogen cycle

The Earth’s nitrogen cycle has been thrown out of balance by human activity. Before the rise of modern agriculture, farms

Most of the nitrogen available to plants comes from compost, manure, and nitrogen-fixing microorganisms, which absorb nitrogen gas (N2) and convert it into 

It is converted into ammonium, a soluble nutrient that can be absorbed by plant roots.

This changed with the advent of the Haber-Bosch Process.

This makes it possible to produce ammonia fertilizer in large quantities on an industrial scale.

The widespread use of synthetic fertilizers has increased crop yields and fed the world's population. But excess nitrates and ammonium have also

Ammonia fertilizer production accounts for about 1% of global energy use and carbon dioxide emissions.

1.4% (the process requires heating the nitrogen and subjecting it to pressures of up to 400 atmospheres, so it is very energy-intensive).

More importantly, fertilizers can lead to increased N2O emissions because farmers often apply fertilizers in large quantities several times a year.

Nitrogen fertilizer is applied but cannot be fully absorbed by crops.

If these fertilizers cannot be fully absorbed by plant roots, some of them will run off into fields and pollute waterways.

The rest is taken up by a range of soil microorganisms, which convert the ammonia into nitrite and then nitric acid.

Salt is then converted into nitrogen. During this process, several steps can produce N2O as a byproduct.

Excessive fertilizers can cause pollution, including the formation of N2O. Fertilizers can be composed of ammonium or nitrate groups.

When roots do not absorb all the nutrients, the remaining fertilizer undergoes a series of microbial-mediated transformations.

Most of the nitrogen is in the form of nitrogen gas (N2), and a small amount is in the form of N2O (a potent greenhouse gas).

Return to the atmosphere.

To reduce N2O emissions, one can carefully allocate fertilizers according to crop needs, or find ways to maintain yields and save fertilizer.

To this end, scientists are trying various methods. One current research strategy is to use precision

Agricultural technology that uses remote sensing to determine when and where to add nitrogen to fields, and how much to add.

Another approach is to use nitrification inhibitors - substances that inhibit the reaction by which microorganisms convert ammonia nitrogen into nitrate nitrogen.

Chemicals that block the production of N2O and keep nitrogen in the soil for plants to grow for a longer period of time

use.

According to the International Institute for Applied Systems Analysis (IIASA),

In 2018, researchers at the Institute of Systems Analysis estimated that by 2030, if these two technologies were widely adopted,

This approach would reduce N2O emissions by about 26% compared to current practices. But researchers say that to help

These are not enough to achieve the greenhouse gas targets set out in the Paris Climate Agreement.

Exploring other strategies.

One possible approach is to harness the potential of certain microorganisms to supply nitrogen directly to plants, as nitrogen-fixing bacteria do with soybeans.

"There is a real gold mine in the soil," said Isai Sa

Isai Salas-González, the 2020 editor of the Annals of Microbiology, said:

One of the authors of an article on plant microbiomes in the Journal of Microbiology and a recent

Just at the University of North Carolina at Chapel Hill

A computational biologist who completed his Ph.D.

Following this line of thought, since 2019, Pivot Bio has launched a product called Pivot Bio

Proven's microbial product is said to work by pouring the inoculant into the furrow where corn seeds are planted.

It forms a symbiotic relationship with the roots of crops. (For sorghum, wheat, barley and rice, the company also plans to

Microorganisms “feed” plants a little nitrogen each time in exchange for sugars exuded by the plants.

This will reduce the need for synthetic fertilizers, said Karsten Temme, CEO of Pivot Bio.

Said.

Taimi said the company's scientists discovered this by isolating a Kosakonia strain whose genome already had the ability to fix nitrogen.

sacchari strains to make the inoculant. Even though these genes were not originally active under field conditions,

But using gene editing, scientists were able to reactivate a set of 18 genes so that

Even in the presence of synthetic fertilizers, nitrogenase can be synthesized.

They start synthesizing this enzyme," Tammy said.

Steven Hall, a biogeochemist at Iowa State University, is currently using large

The product was tested in small, trash-bin-sized containers. Corn was planted in the containers and the researchers placed the inoculant in the containers.

The soil was then treated with different doses of synthetic fertilizers and the corn yield, N2O production, and the

Although the test results are not yet available, Hall said that for "microbial

The hypothesis that biomass reduces the need for fertilizers and thus reduces N2O emissions has been

Preliminary results support this.”

A researcher at Iowa State University at work. To measure the release of N2O, scientists use

A closed box is used to collect soil emissions from which samples are then taken

But some soil scientists and microbiologists are skeptical of this quick fix involving microbes.

Tulum Ma, a graduate student in environmental microbiology at the University of Guelph, Canada

Tolu Mafa-Attoye says "biofertilizers" like this one have had mixed success.

rate, which depends on the soil and environment in which it is applied.

For example, in a wheat field study, inoculation with beneficial microorganisms increased plant growth but produced

There are still many unknowns - as Marfa-Atoyeh's Guelph colleagues wrote in February

In Frontiers in Sustainable Food Systems

For example, whether microorganisms will have a negative impact on soil ecology, or whether they will be replaced by indigenous microorganisms.

beat.

Caroline Orr, a microbiologist at Teesside University in the UK, said:

Orr, a professor of biotechnology at the University of Wisconsin-Madison, says that rather than adding new microbes, it is better to encourage the growth of the desired microbes that are already in the soil.

It was found that reduced pesticide use led to more diverse microbial communities and more natural nitrogen fixation.

In addition, N2O production is influenced by carbon, oxygen and nitrogen – all of which are affected by fertilizer use, irrigation and tillage.