September is the season for harvesting maize in central China's agricultural province of Henan. But Wu Zhenhua is already setting his goals for the next year.

Pointing at vast green farmlands outside Guaiziyang village in Shangcai County in southern Henan, Wu says he will soon seed the field with winter wheat, hoping for bigger output in the summer.

"We had serious drought in the spring, but I managed to raise the wheat output to a record 550 kilograms per mu (8,250 kg a hectare) this year," says the 47-year-old farmer. "I must not rest though. I must prepare for the next season."

Year by year, the hard work of hundreds of millions of crop growers such as Wu during the past 60 years has helped China find solutions to probably one of the biggest challenges on the planet -- feeding almost one fifth of the people on Earth, with only nine percent of the world's farmlands.

Achieving self sufficiency in food supply is often cited as a major success of the People's Republic of China since it was founded in October 1, 1949, following decades of wars and famines. In 2008 China's total grain output hit a record 528.5 billion kg, compared with 113 billion kg in the early 1950s and 400 billion kg in 1984, enough to allay "who-will-feed-China?" worries.

But when China, now one of the world's major economies, celebrates its achievements, the challenge remains: how can it continue to feed its still-growing population in the course of its industrialization and rapid transition to urbanization?

Yin Chengjie, vice chairman of the Agriculture and Rural Affairs Committee of the National People's Congress (NPC), the national legislature, is among many calling for unremitting efforts to secure China's self-sufficiency in grain production.

"China is facing many new food security challenges as a result of rapid urbanization and industrialization," Yin says, The loss of arable land, fewer water resources, and the migration of young rural laborers to cities were major concerns.

The proportion of urban dwellers among total Chinese population has increased to 47 percent from 14 percent in the early 1950s, with more city buildings, roads and factories putting a squeeze on limited land resources.

"This is why the central government has repeatedly vowed to maintain at least 120 million hectares of arable land for grain production. There won't be a basis for food security without enough land," says Han Jun, a rural economist with the Development Research Center of the State Council, a top Chinese think-tank.

Lack of water or access to irrigation facilities is another challenge. Studies show drought leads to about 60 percent of disaster-related losses in grain production each year in China, Yin says.

Population growth in China, estimated to reach 1.5 billion by 2033, means increasing demand for grain, meat, eggs and milk. As millions of young farmers leave their land to seek better pay and opportunities in cities, they turn into grain consumers, further straining food supply, Yin said.

No place is more apt than south China's Guangdong Province to illustrate the challenges.

After the reform and opening up drive of the early 1980s transformed the coastal province into a global manufacturing center and an economic hub, people from all over China flocked here to work at factories.

The province estimates that 30 million of its 100 million residents are temporary or long-term migrants. Meanwhile, the province is now a net grain importer from being a self-reliant producer in the early 1980s.

Yin Chengjie says the Guangdong situation does not necessarily reflect China's whole picture, because the country has managed self-reliance in 95 percent of food for domestic consumption in the past decade.

"But China still needs to pay great attention to food security in the long run because grain is not only a commodity, but also a strategic material for a country of 1.3 billion people," he says.

Part of the answer to food security may be growing in the laboratory of Yuan Longping, renowned for three decades of research and development of high-yield hybrid rice, a staple food of the Chinese.

Based in Changsha, capital of central China's Hunan Province, the 79-year-old scientist is better known as "father of hybrid rice" in China. Since his success in cultivating its first generation in 1974, the high-yield strains have been grown in nearly 60 percent of paddy fields across China. Average output is 20 percent higher than normal rice.

At an international hybrid rice conference last week in Changsha, Yuan said the output of a new super hybrid rice could ultimately reach 1,000 kilograms a mu (or 15,000 kg a hectare) in the next 10 years, three times that of normal rice.

"The newly increasing yield could feed more than 70 million people every year," he said.