Outflowing microplastics ○○ used for rice cultivation goes to the sea and rivers May 18 at 20:20

What kind of image do you think of when you hear "microplastics"?

Many people may think of PET bottles and shopping bags launched on the beach, but this time, we are paying attention to the microplastics from "rice farming."

It has become clear that something unexpected is involved.

(Economics Department Reporter Yosuke Ikegawa)

What is the "unexpected thing" found on the beach?

"There is something I would like you to see about microplastic problems."

I heard from Professor Ken Chiba of Yokkaichi University, who is familiar with environmental issues such as the sea, and I headed for 30 minutes by car from the city center. Yoshizaki coast.

It is the only beach in Yokkaichi that has sandy beaches.

Mr. Chiba and his students have been conducting a fixed-point survey of microplastics contained in beach wreckage once every two months from two years ago.

He showed me a small grain of plastic, which was the most common in the February survey.

The size is about 2 to 4 mm.

It looks like a frog egg, but it can be transparent or light in color.

What on earth is it?

"This is'the empty shell of fertilizer used in rice cultivation'," he

said.

Until now, I have had many opportunities to cover rice cultivation in rice fields such as Akita, Miyagi, and Yamagata, but I did not know that plastic was used as fertilizer.

And it may be flowing into rivers and the sea.

It was said that many plastic shells were found during the farming period from spring to autumn.

Professor Chiba

"I want farmers to manage and use fertilizer shells so that they do not go out of the paddy fields, considering the impact on the environment."

In a microplastic survey conducted at 120 locations nationwide last year by the general incorporated association "Pirika", which conducts environmental surveys, the second largest amount of plastic shells was found after artificial turf.

It started in the 70's

According to the Japan Fertilizer and Ammonia Association, which is made by fertilizer manufacturers, plastics have been used as fertilizers since the 1970s.

Japan Fertilizer and Ammonia Association

"In Japanese rice cultivation, fertilizer is given multiple times during rice planting and summer to promote rice growth. However, farmers need to carry heavy tanks and machines containing fertilizer on their backs and walk around the rice fields. It was a heavy burden due to the change of rice and the scale of farmland. Also, giving more fertilizer than necessary was a burden on the water environment and was a problem. "

The idea was to cover the surface of the fertilizer with plastic.

The fertilizer is covered with a thin plastic, and when a certain amount of water permeates, the shell breaks and the contents dissolve.

The shell is said to decompose when exposed to ultraviolet rays for a long time.

When used with other fertilizers, it has different effects depending on the time difference even if it is sprinkled once, and it is widely used after its release because it reduces the labor of farmers and the burden on the water environment.

It is called "covered fertilizer" or "one-shot fertilizer" and is now used in about 60% of paddy fields in Japan.

Issues that farmers do not even know

However, the fact that plastic is used as fertilizer is not well known among rice farmers.

Masahiro Matsuura (34), a full-time farmer in Miyagi prefecture known for rice, has been cultivating rice for 10 years.

He grows rice with his friends on a large farmland of about 35 hectares.

Mr. Matsuura has used "covered fertilizer" because the work load is light and stable production is possible.

However, until recently, he didn't know that the material was made of plastic and that part of it was leaked into rivers without being decomposed.

Mr. Matsuura

"I thought that fertilizer shells would be decomposed by water, so I was very surprised to hear that plastic remained. I thought about putting a net on the drain, but it would be clogged with garbage. A very difficult problem. It is. "

Local governments and fertilizer manufacturers distribute leaflets and write cautionary notes on fertilizer bags to prevent them from leaking out, but it is difficult to say that they are well known.

Only recently has the country confirmed that plastic shells are leaking out of the paddy fields.

The country will consider measures in the future.

Solution Proposed by high school students

Meanwhile, the private sector is also beginning to seek solutions.

The protagonists are the young people who will lead the next generation of agriculture.

The Miyagi Prefectural Agricultural High School began to think about solutions to this problem, with the students playing a central role when many plastic shells for fertilizer were found in the beach cleanup activities.

Now I'm working with fertilizer makers to research fertilizers that don't use plastic.

We use "Ureaholm", a fertilizer used for gardening.

The feature is that it gradually dissolves in water and the effect appears slowly.

Last year, when we cultivated a test using this, we could confirm the effect of the time difference as well as the plastic shell.

In high school, he is experimenting with fertilizer rice cultivation that does not use any plastic.

We would like to continue research for practical use, including issues such as cost.

Teacher Yamane

"The biggest problem is that the plastic shells used in fertilizer are too small to pick up, so when they flow out, they become microplastic. Many people know this problem through the activities of high school students. I want you to"

In addition, instead of using plastic shells by agricultural corporations in Ishikawa Prefecture, fertilizer is processed into a paste and injected into the soil at different depths so that it will be effective as the rice grows. Cultivation has begun.

There is no doubt that fertilizers made from plastic have supported rice cultivation in Japan, and rice made from it has supported our dining table.

But is it okay to keep it as it is in the future?

I felt that it was an urgent task to consider measures to make Japanese agriculture sustainable.

Reporter of the Ministry of Economic Affairs

Yosuke Ikegawa

Joined the

station in

2002

After working at the Sendai station and Yamagata station, he is currently affiliated.