The rice was not grown in traditional rice paddy, where fields are filled with fresh water, but on a salty beach on the Yellow Sea coast in Qingdao, Shandong.

China has one million square kilometres of waste land, an area the size of Ethiopia, where plants struggle to grow because of high salinity or alkalinity levels in the soil.

Agricultural scientist Yuan Longping, known as China’s “father of hybrid rice”, told mainland media that if a tenth of such areas were planted with rice species resistant to salt, they could boost China’s rice production by nearly 20 per cent.

They could produce 50 million tonnes of food, enough to feed 200 million people, he said.

A research team led by Yuan, 87, recently doubled the output of seawater rice, which in the past was too low for large-scale production.

In the mid-1970s, worrying about how to feed the world’s largest, and rapidly growing, population, the Chinese government started looking for rice species that could grow in salt-soaked fields.

A major discovery was made by Guangdong-based researcher Chen Risheng, who stumbled on a species of red wild rice near a mangrove forest in Suixi county, Zhanjiang. After decades of trait selection, cross-breeding and genetic screening, researchers across the country came up with at least eight candidate species, but their productivity remained low, at two tonnes a hectare, just a third that of ordinary rice and insufficient for large-scale planting.

Last month, at the nation’s largest seawater rice farm, in Qingdao, the output of Yuan’s seawater rice exceeded 4.5 tonnes a hectare, according to state media reports.

Yuan Ce Biological Technology, a Qingdao-based start-up and business partner of Yuan’s team, said it set up an online shop in August, branding the rice “Yuan Mi” in honour of the project’s chief scientist.

The rice now being sold was harvested last year. This year’s crop will enter barns next month.

Each kilogram of “Yuan Mi” costs 50 yuan (US$7.50), or eight times as much as ordinary rice. It is sold in packs weighing 1kg, 2kg, 5kg and 10kg.

Nearly 1,000 people placed an order last month, and six tonnes of the rice had been sold since August, a Yuan Ce sales manager said.

“Our sales revenue target is 10 million yuan by the end of this year,” he said.

The seawater rice was grown on virgin land where no crops had been planted before.

The rice grains have a unique texture and pleasant flavour, according to the company. Consumers pay a high premium not just for the pleasurable eating experience, but also for some potential health and safety benefits.

Professor Huang Shiwen, the leader of the rice disease research team at the China National Rice Research Institute in Hangzhou, Zhejiang, said salt was a disinfectant that could reduce or cut off the transmission of some diseases caused by bacteria.

“To survive in the harsh environment, these species must have some ‘diehard’ genes which may enable them to better resist the attack of certain diseases or bugs, especially those happening at the root or lower stalk,” he said.

This could reduce the use of pesticides and lower the risk of exposure to harmful chemicals in the food chain, he said.

The seawater rice developed by Yuan and other research teams is not irrigated by pure seawater, but mixes it with fresh water to reduce the salt content to 6 grams per litre. The average litre of seawater contains five times as much salt.

Researchers said it would take years more research to develop a rice species that could grow in pure seawater.

Professor Zhu Xiyue, an economics and policy expert at the national rice institute, said the seawater rice project would help secure China’s food supply by turning “waste land to green fields”.

“The output may be low and price high, but they can increase China’s total area of arable land, which can be used and save many lives in hard times,” Zhou said.

China is already the biggest of importer of some major agricultural commodities, according to a report by the Stockholm International Peace Research Institute last year.

Zhou said the land area of some coastal provinces was increasing, as big rivers such as the Yangtze and Yellow River dumped enormous amounts of sediment into the sea.

“The seawater rice can be the first settler on this new land mass,” he added.

But the project also has its critics.

Liu Guangfei, a wasteland treatment expert at Beijing-based Eagle Green Technology Development, said Yuan’s rice could not be planted in inland provinces such as Heilongjiang and Xinjiang, which had more than 90 per cent of the saline and alkaline soils in China.

The chemical composition of inland soil varied significantly from that on the coast, he said. Yuan’s rice was mainly resistant to sodium chloride, but waste land in inland areas had high levels of sodium sulphate, which could be detrimental to the rice.

He also doubted whether planting rice would be of long-term benefit in treating waste land.

“Planting this rice will keep the land salty forever,” he said. “It cannot be used to grow other crops.”

Liu said there were other commercial plants that could survive in such soils, such as jujube and wolfberry, that could significantly reduce salt water levels in fields after a few year’s of fresh water irrigation.

But the biggest challenge to the seawater rice project was that China now had a surplus of rice.

“China is not in food shortage any more,” he said.