SUNLIGHT in the Pearl River Delta glistens off the patchwork of fish ponds like a golden tribute to the ken of Cantonese peasants. Generations of farmers here have created some of the world's richest and most efficient farmland - and a model for third-world agriculture.
The peasants have turned waterlogged soil into series of fish ponds and verdant dikes - a cyclical system in which the waste or residue from one crop or animal becomes the nutrient or food for another.
The dike-pond system conforms with nature more than do most farms in developed countries. It uses only organic materials, requires no costly fertilizers or equipment, and does not pollute the environment or erode the soil.
It is a vital achievement for a developing country struggling to grow more food for a burgeoning population.
To try to duplicate what peasants have fashioned here over four centuries, the United Nations has helped fund a $31 million project to plow 81,500 acres of Guangdong Province marsh this year into a gridwork of dikes and ponds. West Germany is supporting a similar project in the African nation of Malawi.
Encompassing more water than soil, the delta is a place of warm mud, skimming punts, and black nets slung on railings to dry. Water is never farther away than the length of a bamboo pole. Li Niu is one of thousands of dike-pond farmers who keeps a menagerie of fish, livestock, insects, plants, plankton, and bacteria on just two acres of land for perhaps the highest per acre agricultural profits in China.
Mr. Li grows mulberry trees on dikes next to his pond, feeds the leaves to silkworms, and sells the cocoons to neighboring filatures. He dumps the excrement from the silkworms into the ponds to feed the five types of fish he breeds to earn the bulk of his income.
Next to the pond Li raises 20 pigs a year, pitching the waste of what Chinese call ``walking fertilizer factories'' into the pond to nourish plankton, the food for bighead carp and silver carp. He also feeds the fish elephant grass that he grows next to his mulberry trees and gathers water hyacinth, duckweed, and water lettuce from neighboring canals for the grass carp and pigs.
``If fish are coming up to the surface for air in the morning, then I know I've put too much in the pond,'' Li says. He waits a day or two before adding more materials, allowing the oxygen level in the water to rise.
On the shore Li also cultivates taro and sweet potato, while many of his neighbors keep ducks. Completing the cycle of the dike-pond system, three times a year he spreads the rich mud from the bottom of his pond onto the roots of his mulberry trees.
From this hodgepodge harvest Li earns $6,200 a year for his family of six, an astronomical sum compared with the $125 annual income of the average Chinese peasant. With funding, developing countries could turn wetlands into bountiful dike-pond farms, says George Lai Chan, an engineer at the Canton Institute of Geography.
Yet environmental specialists agree that other areas in China and elsewhere may not match the cultural, geographical, or historical circumstances that have made this delta ideal for the dike-pond system: The Pearl River provides fecund silt; the cities of Canton and Hong Kong, a profitable market for the region's cash crops.
Delta farmers have also faced less state meddling than their counterparts in other areas of China. Guangdong Province has always been at the end of Peking's reach, particularly since the last imperial dynasty closed all ports but Canton to foreign trade in the 18th century.
Moreover, Confucian traditions have helped make the family the most common and productive farming unit in China. Such a small, close-knit group is ideal for running the compact and complicated dike pond.
``Everyone from Granny to the kids has a role in the dike-pond system, each helps out according to their abilities - from gathering greens for the pond to feeding the fish,'' says Kenneth Ruddle, who did out a three-year study of the system for the UN University in Tokyo.
Although Africa doesn't match the ideal conditions here, West Germany has funded a four-year dike-pond project in Domasi, Malawi, since 1986. Malawi is helping farmers raise banana or maize on dikes and tilapia in ponds over a total area of 12 acres, says Dr. Ruddle.
``The Chinese dike-pond system is not completely transferable. It's too complex and too tightly administered, and you can never move such projects from one culture to another without some changes; but the basic idea of the dike-pond integrated farm is fantastically sound for many subtropical and tropical areas.... We'd like to spread such farms throughout much of the continent,'' he says.