March 9, 2023
BEIJING – Crops help produce more arable land for nation
The importance of food security was emphasized in autumn by Xi Jinping, general secretary of the Communist Party of China Central Committee.
In his report to the Party’s 20th National Congress, he said, “We will ensure that China’s food supply remains firmly in its own hands.”
China’s northeastern provinces, where the winter permafrost is more than 1 meter deep, are home to about 10 million hectares of saline land
Xi also underlined the Party’s determination to ensure that China’s total area of farmland does not fall below 120 million hectares.
Agricultural experts stressed the importance of guarding this bottom line firmly and also advised turning another 100 million hectares of saline-alkali soil, also known as saline soil, into arable land. This soil contains so much salt that barely any crops can be grown on it.
Liu Jiayin, director of the Qingdao Saline-Alkali Tolerant Rice Research and Development Center, said: “Most crops die if the salt content in water is more than 0.2 percent. The amount of salt in saline soil ranges from place to place in China, but it is above that level, thus making it hard to support the growth of crops.”
Data from the center show there are 950 million hectares of saline land globally. Some 22 percent of this land is in East Asia, and China has 100 million hectares of saline soil and 128 million hectares of arable land.
Some 6.67 million hectares of saline land is located in coastal areas around Bohai Bay and near the southeast coast. This land, the result of coastal erosion, will retain its salt content for a long time.
The nation’s northeastern provinces, where the winter permafrost is more than 1 meter deep, are home to about 10 million hectares of saline land. In spring, water on the surface evaporates, but deeper down it remains frozen and cannot escape. As a result, salt accumulates and the soil becomes saline.
A further 66.67 million hectares of such land is located in the northwest, where there is so little rainfall that salt on the surface is seldom washed away.
Wei Ke, an associate researcher at the Chinese Academy of Sciences’ Institute of Atmospheric Physics, said annual rainfall of 400 millimeters divides “wet” and “dry” regions, while 200 mm of rainfall a year determines “dry” and “very dry” areas.
“Most of the saline land in the northwest is located in dry or very dry regions,” he said.
Wang Qingxue, 60, a farmer in Dongying city, Shandong province, said: “The saline soil on my family’s arable land is near the Yellow River, while that of my cousin is near Bohai Bay. Both areas can be exploited, as they are close to wetlands, so this soil is not such a big problem.”
Dry areas of the country are the biggest problem. For example, in Lankao county, Henan province, saline soil accounts for 36 percent of the total agricultural land. Combined with wind and sand, this situation has posed major challenges to local agriculture.
A vicious circle formed. Dry weather turned the soil saline, which meant it could not support plant or crop growth. As a result, there was no natural barrier against the wind, while sand that accumulated worsened the condition of the soil, so it was unable to retain water.
Even good arable land was affected, as evidenced by Shen Tianmin, a wheat breeding expert from Kaifeng city, Henan, who said in 1962 that wheat production in Lankao was only 12 kilograms per 0.67 hectares.
Two years later, Jiao Yulu, 42, the Lankao Party chief, who led locals in transforming 6,000 hectares of saline soil into arable land, died from liver cancer. In 2017, Lankao eradicated poverty after transforming a high percentage of saline soil into arable land to support crop growth.
Salt-tolerant rice can grow in saline soil with water containing 0.6 percent salt, which covers a relatively high percentage of China’s saline soil, thus increasing the nation’s rice production.
In the past four years, the Qingdao center has planted seawater rice on 6.67 million hectares of land nationwide, yielding a record-high 698.4 kg per 0.67 hectares last year
Zhang Guodong, vice-director of the Qingdao research center, said, “Quite a high proportion of saline soil in China has a salt content of more than 0.6 percent, but by watering the rice plants, we keep the salt content in water surrounding their roots at around that level, thus helping them grow well.”
In 1930, it was discovered in Ceylon — now Sri Lanka — that wild rice could grow in saline soil, marking the start of research in this field.
In comparison, such research in China did not begin until the 1980s, when Chen Risheng, an agricultural scientist in Zhanjiang city, Guangdong province, found that some rice plants could grow on the coast in this area.
Chen collected more than 500 seeds and grew them on an area of local wetland. After five years, he harvested 3.8 kg of seeds that had grown steadily — naming the crop Sea Rice 86 to mark the year in which he made the discovery.
After decades of research, China took the lead globally in seawater rice research thanks to the late academician Yuan Longping, known as the “father of hybrid rice”, and his team.
Zhang said, “Seawater rice breeding is part of hybrid rice breeding, in which China has long been the undisputed champion of the world.” In 2012, Yuan and Chen set up a team to research seawater rice. By 2016, Yuan had coordinated national resources and founded the Qingdao Saline-Alkali Tolerant Seawater Rice Research and Development Center.
Yuan set three goals for the pair: Seawater rice must be able to withstand water with a salt content of 0.6 percent or more, thus saving water resources; to be economically sustainable; the yield must reach 300 kg per 0.67 hectares; and the total plantation area should be more than 6.67 million hectares for planting seawater rice to be a sustainable industry in China.
The Qingdao center turned to a range of innovations to work toward these goals, including gene sequencing to locate genes that enable the rice plant to tolerate salt and alkali, and hybrid breeding to accumulate as many salt-tolerant genes of a single rice plant as possible to reproduce such plants.
The center also signed contracts with China Aerospace Science and Technology Corp for seawater rice seeds to be transported into space.
The measures adopted enhanced the efficiency of breeding seawater rice. On Dec 5, the first batch of rice seeds grown in space returned to Earth with three astronauts on the Shenzhou XIV spaceship after spending 120 days on China’s space station.
The first two goals set by Yuan have been met as a result of the measures taken.
In 2017, the Qingdao center developed seeds that yielded 620 kg of rice per 0.67 hectares in water containing 0.6 percent salt. In the past four years, the center has planted seawater rice on 6.67 million hectares of land nationwide, yielding a record-high 698.4 kg per 0.67 hectares last year.
In addition, Chinese teams have received invitations from nations with large areas of saline soil to share their technologies with them.
In July 2018, Khaleej Times, which is based in Dubai, United Arab Emirates, reported that a team of Chinese scientists had started harvesting rice in diluted seawater, aiming to cover about 10 percent of the UAE with paddy fields to increase grain output on the sand-covered land.
Chinese teams are now cooperating with local officials on seawater rice projects in many other countries.
There are challenges to seawater rice research, including the belief among some that it is not worth investing in such endeavors, as the flavor of the rice is not that good.
Liu Hongzhi said seawater rice is one of several types of salt-tolerant plants that can be used to transform saline soil into arable land, with salt-tolerant grass and beans also fulfilling this function
Despite this, seawater rice is being sold on domestic e-commerce platforms, with many customers saying it tastes delicious.
One netizen said, “The name led me to think that the rice might be salty, but when I tasted it, I realized this was far from the case.” Another netizen commented, “It tastes exceptionally well.”
Liu, from the Qingdao research center, said: “The roots of seawater rice plants can draw nitrogen, phosphorus and potassium, making saline soil more fertile. The roots also make this soil porous, while the microbes that grow in them improve bacteria groups,” she said.
It is necessary to see the “big picture” regarding seawater rice, which is important not only for producing hundreds of kilos of food, but also for turning soil previously unfit for cultivation into arable land, Liu said.
“That is the most significant point of seawater rice — it can help increase the amount of arable land without diminishing the nation’s forests or grasslands,” she said.
Liu Hongzhi, senior researcher and vice-secretary-general at the Chinese Society for Environmental Studies, said seawater rice is one of several types of salt-tolerant plants that can be used to transform saline soil into arable land, with salt-tolerant grass and beans also fulfilling this function.
She said such plants will perform better if land is divided into small square areas to conserve water. “We need to gain more experience to further popularize seawater rice,” Liu Hongzhi added.
Wei, from the Chinese Academy of Sciences, said ways need to be found to transform saline soil in the northwest of the country into arable land. “Seawater rice teams have done a good job, but they could face a long road ahead,” he said.
Seawater rice has further development potential, and its water-saving benefits should not just be compared with other types of rice, but with plants such as potatoes, Wei said. Only when they can save the same amount of water as potato plants will seawater rice plants become more popular in the northwest, he added.
With vast areas of saline soil being turned into arable land in the future, the efforts made today to make this possible will mark a significant breakthrough.
Zhang said seawater rice could be used to increase the amount of arable land in China by some 6 or 7 percent.
More important, this land could be used without it encroaching on forests or grasslands. By greening previously grassless land, seawater rice helps improve the environment for everyone, Zhang added.
Yuan, the “father of hybrid rice”, once said: “Of the 1.5 billion mu (one mu equates to 0.67 hectares) of saline land in China, seawater rice can be grown on 200 million mu. If every mu produces 300 kilograms of rice, we will have 50 billion more kilograms of rice, enough to feed another 200 million people.”
The dream of the late scientist, as well as that of China’s 1.4 billion people, is set to be realized.