"In Dingxi, the scanty rainfalls concentrate in early autumn, which is enough to guarantee a good harvest of potatoes," said Wang Yihang, a leading potato expert in the province.

With an annual output of 5 million tons, Dingxi now grows more potatoes than any other city in China. One-third of the city's arable lands are devoted to potatoes.

Also, local officials credit potatoes with helping to solve the food problem just as the new millennium began. And as the city grew richer, incomes widened thanks to the potatoes

"Potato-processing has become our pillar industry. Over 20 local plants process the extra potatoes into starch and popular snacks," said Yang Zixing, party secretary of Dingxi. According to Yang, the factories are now the source for one-quarter of farmer incomes.

But local officials say the edible tubers are not the only driving force behind the rise of Dingxi, as the city has also succeeded in cultivating other economic crops.

Longxi, a mountainous county of Dingxi, has become a national base for Chinese angelica, astragalus, and other medicinal herbs whose roots are used as popular tonics in traditional Chinese medicine (TCM).

Like potatoes, the edible parts of the herbs are buried underground and can therefore survive droughts and catastrophic hailstorms, local officials explained.

In recent years, a new technology has also allowed local farmers to grow corn, which would normally have withered away on Dingxi's barren lands.

After the autumn rain replenishes the soil with water, corn farmers cover the entire field with plastic membranes to prevent evaporation, storing enough water to grow corn.

With the help of the membranes, one hectare of corn field can yield 7.5-15 tons of corn and at leaast 45 tons of straw for animal feed every year, said Yang Qifeng, vice head of the provincial department of agriculture and animal husbandry.

The evolution of Dingxi from a land of famine to agricultural exporter shows the untapped agricultural potential of China's vast but impoverished west.