The findings suggest that desertification, a longtime scapegoat for frequent sandstorms in north China, is not solely to blame.

"The dry and vulnerable topsoil in north China's spring farmland can be easily picked up by gales," said Jin Heling, expert with the Institute of Environment and Engineering in Cold and Arid Regions under the Chinese Academy of Sciences (CAS).

About 53 percent of China's land, mainly in the north, is in drought and semi-drought areas.

"Sandstorms are usually triggered by sudden temperature changes in springtime, poor vegetation cover and aridity, but exposed farmland where abundant soil can be blown away is also a major cause," said Kang Ling, Vice Director of the Observatory of the Inner Mongolia Autonomous Region in north China.

The intensive land cultivation of furrowing and harrow - plowing the land before planting crops - is seen as one of ancient China's breakthroughs and greatly boosted agricultural output.

Environmentalists, however, point out that large quantities of topsoil in plowed farmlands are blown across North China every spring, the time for annual plowing.

Researchers with the Division of Earth Science of the CAS based their study on the diameter of the granules in the recent sandstorms and insist that dust in sandstorms was mainly from farmlands.

The CAS research is backed up by Gao Huanwen, professor with the China Agricultural University, whose study shows that sandstorms in Beijing mainly originate from cultivated lands, dry river basins and degraded sandy pastures around Beijing, which is less than 250 kilometers from an encroaching desert.

"Generally speaking, desert sands are hard to 'take off' because the granules are relatively big, but tiny and light soil granules in plowed farmland can be easily 'gone with the wind,"' Jin said.

The most serious sandstorms of the year are usually witnessed in March and April - north China's spring plowing period. As shown in the past two months, at least 10 major sandstorms hit north China including Beijing, making it "the worst sandstorm weather in the spring season for the past decade."