Green Intelligencer: The straw that broke the earth’s back: The world’s first “weight loss” secret for agricultural land

Farmers over-fertilize, a large amount of nitrogen fertilizer residue soil, derived from environmental pollution problems.

There is a saying in rural areas “crops a flower, all depend on fertilizer home”, nitrogen fertilizer is the largest amount of fertilizer used in agricultural production, to improve crop yields, but also “planted” environmental ecological pollution.

“This is the beauty and sorrow of nitrogen fertilizer.” Taiwan Academia Sinica Institute of Molecular Biology special researcher Yifang Cai slowly open the box, “some people say, spend a dollar to buy fertilizer, to spend four dollars to deal with environmental problems.” Nitrogen fertilizer test the earth’s tolerance, there is as pivotal as the straw.

Taiwanese botanist joins the American Academy of Sciences

Cai Yifang is an internationally acclaimed botanist and has just been elected to the National Academy of Sciences. (Courtesy of Taiwan Central Research)

She is the first scientist in the world to find the key gene for nitrogen fertilizer absorption in plants. With her short hair and wheat-colored skin, she is very different from researchers who are locked in the laboratory. The National Academy of Sciences (NAS) announced on April 26 the latest list of selected members, foreign members of only two Asian scientists, one of which is Yifang Tsai, she is also the first female scientist in Taiwan was elected as a member of the U.S. Academy of Sciences.

It was midnight in Taiwan when the list was announced. Yifang Tsai opened her computer to receive a letter the next day and was told to attend an online meeting to welcome the new Fellows, “Am I going to celebrate someone else’s election, or am I being elected?” Questions popped up in her head, and later when she opened the letter with the elected list again, “It was like I was looking at a college list and found my name.” She still couldn’t believe it when she walked out and told her labmates, “I think I’ve been elected to the American Academy of Sciences.”

When Yifang Tsai returned from her studies in the U.S., she made a promise to herself that she would “base herself in Taiwan and become internationally famous. Nitrogen fertilization is harmful to the environment.

Over-fertilization is killing the lifeblood of the planet

Nitrogen fertilizer pollution has led to severe eutrophication along China’s coast, with oily green algae covering the sea and a steady stream of voices for weight loss on agricultural land.

“The introduction of nitrogen fertilizer was an important part of the green revolution, with nitrogen fertilizer, crops increased, and just after the green revolution, the global population also increased dramatically, with sufficient food to feed humanity.” Cai Yifang talked about the beautiful beginning, however, sorrow followed the surface, “after the application of nitrogen fertilizer, crops may really absorb less than half, or even one-third, excess nitrogen fertilizer in the soil and can not stay, because nitrogen fertilizer will soon be converted into nitrate, nitrate is negative electricity, soil particles are also negative electricity, negative and negative repulsion, with the rain washed into the river, and finally into the The ocean.”

Nitrogen fertilizer pollution is raging, Cai Yifang pointed out that nitrogen fertilizer will cause coastal waters eutrophication, that is, increased nutrients, algae proliferation, once the algae proliferation, the next area will gradually lack of oxygen, fish and shrimp and other marine life is difficult to survive, the formation of the “dead zone” (dead zone).

Global agriculture consumes more than 100 million tons of nitrogen fertilizer each year, only 50 million tons are estimated to be absorbed by plants, and since 1950, the global area of the dead zone along the offshore has increased significantly by 10 times. “This is closely related to nitrogen fertilizer pollution.” Cai Yifang explained, “After 1950, the massive use of nitrogen fertilizer, the death domain problem has also come to be more serious, first appeared in the United States along the coast of Seattle, however, with the local reduction of nitrogen fertilizer use, now the death domain has disappeared, the most serious overuse of fertilizer is now in Asia.”

China is the world’s largest consumer of nitrogen fertilizer, with an average annual agricultural nitrogen fertilizer application of about 22.8 million tons from 2010 to 2019, according to China’s National Bureau of Statistics. Cai Yifang analyzed that the amount of nitrogen fertilizer used per unit area in China is three times that of the United States and Japan, but the yield is at best the same, or even only 70%, which means that nitrogen fertilizer is applied more and wasted, and the yield is not increased, but instead causes environmental problems.

“The dreamy blue tear scene is the result of eutrophication.” Cai Yifang took the tourist spectacle that has become popular in recent years as an example, from the Pingtan sea in China’s Fujian province to the coast of Matsu in Taiwan, there is a proliferation of whirlpool flagellate algae called “blue tears”. In recent years, China’s coast every year there is a large outbreak of algae, the Yellow Sea was once covered with nearly 30,000 square kilometers of seaweed, the death of the domain crisis surfaced, these and nitrogen fertilizer are not unrelated.

What is sad is not only the eutrophication of the waters, but also the nitrogen fertilizer is a killer of global warming. Cai Yifang explained that the nitrate and nitrogen fertilizer left in the soil will be converted to nitrous oxide (N2O), which is a greenhouse gas, 300 times stronger than the effect of carbon dioxide (CO2). Scientists from the National Oceanic and Atmospheric Administration (NOAA) have published a study in the international journal Science, pointing out that nitrous oxide has become the new major ozone-destroying substance, and agriculture is one of the important sources of nitrous oxide emissions.

In the early twentieth century, German scientist Fritz Haber and engineer Carl Bosch invented synthetic nitrogen fertilizer by mixing nitrogen and hydrogen at high temperatures and pressures in what is known as the Haber-Bosch process. “The nitrogen bonding in the air is quite strong, and this is imitating the bomb principle to make nitrogen fertilizer, which consumes quite a lot of energy.” Yifang Cai further explained, “Two percent of global energy is spent on the manufacture of nitrogen fertilizer.”

Deciphering the mechanism of nitrogen fertilizer uptake by plants

China is the world’s largest consumer of nitrogen fertilizer, using three times more nitrogen per unit area than the United States and Japan. (Reprinted from Our World in Data)

Farmers have been applying excessive nitrogen fertilizers for a long time, pursuing high yields while ignoring the futility and environmental costs of applying more. Yifang Cai kept studying how plants suck nitrogen fertilizer in from the soil, taking Arabidopsis thaliana as the research object, and found the nitrate transporter protein CHL1 on plant cell membranes, cracking the enigmatic molecular biological mechanism one after another, and also proposing a heavy scientific basis for agricultural land to lose weight and reduce pollution.

“These transporter proteins are responsible for transporting nitrate from the outside of the cell to the inside, and are also responsible for detecting the amount of nitrate in the soil, which is very smart and arithmetic, and makes different responses according to the nitrate concentration, so the plant is very precise in regulating how much to absorb and how much to metabolize.” Yifang Cai explained the transport and conduction mechanism of the plant body, “It is the gatekeeper, at the same time it is the porter, it is also the transmission center.”

“Obviously, it is going to be saturated, and over-fertilization is useless because the plant will shut its mouth and stop eating.” Yifang Cai summarized the research findings in popular science language, “We also found a brand new mechanism to understand how plants know how much nutrients are available, and other nutrient sensing can be done through this model to see if there is the same mechanism.”

The big national problem of agricultural land weight loss

Agricultural policy plays an important role in the killing of the earth by the misuse of fertilizers.

Looking around the world, China’s crop nitrogen use efficiency has always been respectful. According to a study by Xin Zhang, an assistant professor at the University of Maryland, China’s nitrogen use efficiency is only 25 percent, far below the global average of 42 percent, and for global nitrogen use efficiency to increase from 42 percent to 70 percent, China would have to return to the 60 percent level of the early 1960s to ensure that the earth’s carrying capacity is in a safe range.

Ironically, while terrestrial food production capacity is built on a large amount of chemical fertilizers, the production of marine granaries is instead declining. Cai Yifang believes that the low efficiency of nitrogen utilization is not only a waste of money, while intensifying environmental risks, this side of the application, flow over there, and ultimately into the sea, is the same as fertilization of the sea, fish and shrimp habitat is destroyed, Taiwan’s nearby sea catch is getting smaller and smaller, may also have a correlation with nitrogen fertilizer.

In the end, how can nitrogen fertilizer in agriculture and the environment to achieve a balance point? Cai Yifang suggested that the rationalization of fertilization, a small amount of food is the best practice, many crops over-fertilization will also inhibit growth, each plant has different characteristics, the environment, weather and other factors will also affect the nitrogen utilization rate, so depending on the different conditions to fertilize, the mask to the line.

In addition, the key to losing weight on agricultural land also involves policy guidance, and China’s subsidies for fertilizers are often criticized. Cai Yifang said, if the price of fertilizer is set high, no one is willing to over-fertilize, but some agricultural policies are instead to suppress the price of nitrogen fertilizer, which is an undesirable policy.

To find a win-win solution for agriculture and the environment, international scholars have been applying Cai Yifang’s findings to explore the nitrate transporter proteins and genomes of different crops. Researcher Chengcai Chu of the Chinese Academy of Sciences found that indica rice has better nitrogen utilization efficiency than japonica rice and is more able to grow in poorly ridged soils, and later found that the nitrate transporter proteins of indica and japonica rice have a different amino acid sequence, causing a significant difference in nitrogen utilization efficiency between the two.

Scientists are simultaneously working to improve the nitrogen uptake rate of plants, and Yifang Cai’s research team has also invested in related experiments. She pointed out that “plants will send the nitrate stored in older leaves to younger leaves to maintain the growth of younger leaves, and we try to strengthen this redistribution mechanism through genetic engineering modifications to increase the nitrogen utilization efficiency of plants, and experiments have shown that Arabidopsis can increase production by 20 percent, and rice by about 8 or 9 percent.”

“My very scientific decision to go into botanical research in the first place was a very romantic beginning, because I grew up loving plants and my family thought I was a freak with eyes for plants.” Yifang Cai talks easily about the inspiration given to her by plants, “In the face of difficulties, the first idea of animals is to run away from difficulties and survive if they run fast, but plants can’t run, they have to face it and solve any difficulties, I am exploring the secrets of plants and know what strategies it actually uses to fight various adversities.”

The current abuse of fertilizers triggered the environmental pollution crisis, humans should perhaps learn from plants, bravely face the problem and turn the Earth’s plight.