Organic farming produces food that is priced two or three times higher than food without organic certification, but it is popular with consumers who see it as healthier.

This new - but essentially very traditional - agricultural technique excludes or strictly limits the use of manufactured fertilizers, pesticides, plant growth regulators and genetically modified organisms.

It relies instead on techniques such as crop rotation, biological pest control and "green manure" - a crop of, say, legumes and grass that is dug in to return nutrients to the soil or is cut and left on the surface as mulch. Organic foods are not processed using irradiation, industrial solvents or chemical additives.

Jiang Gaoming, a researcher at the Institute of Botany, Chinese Academy of Sciences, and his team have been learning organic farming on experimental plots in Pinghu county, Shandong province, since 2007. They used wheat straw as feed for stock and used the animal waste to fertilize vegetables. Trapping lamps were put out for insects, and farmers killed weeds by hand.

The researchers are trying to ascertain the costs and earnings from farming without chemicals, but Jiang said they don't yet have the details they need to issue a report.

He said widespread expansion of organic farms will require increased technical training, higher initial investment and, of course, more farmers willing to make the switch. But he remains optimistic.

"Less than one in a million people eats organic food regularly in China, which shows that there is great potential in the market," he said.