Soil conservation in China's Loess Plateau

Excerpt

SOILS in the Loess Plateau of northwestern China are perhaps the most seriously eroded soils in the world. The reasons for this are threefold: First, the loess surface soils, while fertile, are soft and loose. Second, intense rainfall is concentrated during the short summer season, July through September. Third, the original cover of grass and trees was long ago destroyed by fanning activities, which the region's inhabitants have carried on for several thousand years.

The magnitude of soil loss

Annual soil loss in the 1.1-billion-acre region ranges from 5 to 112 tons per acre. But on some of the 33 million acres of farmland, annual soil loss exceeds 135 tons per acre. Areas with a comparatively flat, smooth loess surface, of course, suffer the least erosion. The tops of loess hills, which are narrow and small, are somewhat more erodible.

The most serious erosion occurs in gullies as a result of down-cutting erosion, head-ward erosion, and riverbed expansion. Headward erosion in some areas is particularly serious. For instance, the head of the Black-wood Gully in Luo Chuan County of Shaanxi Province, has expanded nearly 1,150 feet in the past 200 years …