About 3,000 years ago, an ingenious form of agriculture was devised on the high plains of the Peruvian Andes. It employed platforms of soil surrounded by ditches filled with water. For centuries this method flourished because it produced bumper crops in the face of floods, droughts, and the killing frosts of those 3,800-m altitudes.

Now, in a dramatic resurrection, modern-day Peruvians working with archeologists have reconstructed some of the ancient arms, and the results have been amazing. They have found, for instance, that this method can triple the yield of potatoes. In at least one experiment, potato yields outstripped those from nearby fields that were chemically fertilized.

In 1983, the water in restored canals helped irrigate crops during a severe drought that damaged conventional fields in the area. Three years later, the elevated fields survived heavy flooding that inundated neighboring flatlands.

In Cutini Capilla, an Aymara community on the western shore of Lake Titicaca about halfway between Puno and the ruins of the ancient Tiwanaku capital, 53-year-old Luis Tulco said the raised fields his village built five years ago are doing well.

``Before, this area always flooded, but now we have waru warus and this land is useful,'' he said in heavily accented Spanish as he stood at the edge of an elevated field of purplish quinoa under an enormous blue sky.

Cesar Mamani, the 45-year-old president of the 65-family community, agreed.

``Old techniques remind us of our ancestors and our ancestors had good ideas,'' he said.

Waru waru has been used in many countries like China.