TOKYO — Toshiharu Ota, a rice farmer in Miyagi Prefecture, in northeastern Japan, survived the earthquake, tsunami and nuclear disaster last year. But his fields were devastated by the salt deposits left behind when the tsunami’s floodwaters receded. Now, to help farmers like Mr. Ota, a research team is working to develop a new salt-tolerant variety of rice.
The tsunami’s waves, up to 40 meters, or 130 feet, high engulfed the coastline around Ishinomaki City, where Mr. Ota lives, devastating hundreds of thousands of lives and washing away whole sections of towns, neighborhoods and farmland.
Miyagi Prefecture has estimated the cost of damage to agricultural land and facilities at ¥381 billion, or $4.6 billion, making it one of the prefectures hardest hit in economic terms by the disaster.
Rice has traditionally been a leading crop in northeastern Japan. Miyagi Prefecture’s 2010 harvest fetched $818 million. But last year the harvested rice acreage fell short of target by 4,600 hectares, or 11,400 acres, according to the agriculture ministry. In total, 11 percent of the prefecture’s farmland was damaged.
More than a year after the disaster, many farmers like Mr. Ota are still struggling to cope with the economic consequences. Even leaving aside the widespread fallout of radioactive elements released from the Fukushima Daiichi Nuclear Power Plant, the tsunami left the soil of coastal farmlands damaged by sodium chloride from the sea water.
Mr. Ota, who farmed 11 hectares of rice paddies, said nearly half were flooded. Local workers have labored hard to remove salt from the soil in the past year. Still, nothing has been the same since.
“Even with desalination, the yield has dropped,” Mr. Ota, 56, a sun-tanned, fifth generation farmer with graying hair, said during a recent interview.
Once dissolved into the soil, salt is hard to remove. It tends to stick to other elements and comes out only when plant roots emit an acid that breaks away minerals, including sodium chloride, to be absorbed by the plant, he said.
“When I test the soil for sodium, the reading comes out clean, but when I actually grew rice, the crop did not do well,” Mr. Ota said.
To help farmers like him, a team of scientists has been working to speed up development of a new salt-tolerant rice variety, with the aim of making it commercially available in a few years. The project involves heavy ion beam technology developed by the prestigious independent research organization Riken.
Working on the project with Riken are researchers at Miyagi Prefecture’s Furukawa Agricultural Experiment Station in Osaki City and Tohoku University in Sendai, the chief city in the prefecture.
“We’ve had success in developing one variety of salt-resistant rice, although this variety doesn’t taste that great,” said Tomoko Abe, research group director of accelerator applications at Riken’s Nishina Center in Wako city, north of Tokyo, last month.
Salt damage can cut the yield of a rice crop in half. “With the rice variety we’re developing we should see the yield only drop by 20 percent,” Ms. Abe said. “We should also see less fragmented rice.”
Mainly used in nuclear physics and also in medical applications like cancer treatment, heavy ion beam technology was first applied by Riken to speed up mutations in plants in 1989. Ms. Abe helped to develop the world’s first salt-tolerant rice variety, based on the Nipponbare rice strain, in 2006.
Compared to more traditional types of plant mutation techniques, using x-rays or gamma rays, plants need to be exposed to only a low dosage of powerful heavy ion beams for a short time — seconds and minutes instead of hours, days or weeks — for a high likelihood of mutation to occur. The survival rate of the exposed plants is high, moreover, because the highly focused beam does less damage to their overall DNA.
“It takes 10 years to develop a new breed using traditional methods, but Riken’s method shortens the cycle considerably,” said Takashi Endo, a researcher at Miyagi Prefecture.
In the year since the tsunami about 5,250 hectares of farmland in the prefecture have been desalinated, including rice paddies. The prefecture aims to clean up an additional 4,100 hectares this year and a final 3,650 hectares in 2013.
“We’ll be seeing more regions restarting farming this year, but some areas will still be unable to farm,” Mr. Endo said.
The introduction of salt-tolerant rice varieties could also help the region cope with another problem — land subsidence. Miyagi and surrounding coastal farmlands now face a higher risk of saltwater damage, experts say, because the earthquake’s seismic shift caused large parts of northeastern Japan to sink.
In Mr. Ota’s case, his farmland has sunk by about 80 centimeters, or 2.6 feet. Closer to the epicenter, the subsidence is greater. Oshika Peninsula, just a short drive away, was the closest place to the epicenter of the offshore quake. Land there sunk by 1.2 meters and slid horizontally eastward by 5.3 meters, according to the Geospatial Information Authority of Japan.
“We’ve been in a terrible situation,” Mr. Ota said. “We’re not dealing with just seawater but also flooding from storms. We have a sharp increase in drainage water that lingers on our farmland.”
Discharged storm water used to recede in a day: Now it takes up to a week to drain away. “It’s been overwhelming,” he said.
Having the option to grow a sodium-tolerant variety of rice may determine whether some farmers can continue to stay in agriculture, said Kazuhisa Matsunaga, who works for Zen-noh Miyagi, an agricultural cooperative.
Some coastal farmlands have dropped almost to sea level. “Those areas would need to raise their land considerably to continue to use the existing variety of rice,” Mr. Matsunaga said. “It would make a difference for them to be able to continue farming using a variety that would be forgiving to soil that has some sodium left.”
Mr. Endo said it could take two years to develop a salt-resistant variety and another two years to grow enough of the seeds to bring it to commercial scale.
Faced with the long-term worry that cesium will be detected in their crops and consumer anxiety over radioactivity in anything grown, raised or caught near Fukushima, Miyagi Prefecture’s farmers will have to overcome daunting challenges if they are to stay in business.
“We hope that our research results will be a bright spot for farmers affected by the disaster,” Mr. Endo said.
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