together—the vetiver in the front blocking soil loss down-slope and the leucaena behind benefiting from the accumulated moisture and soil.
In some locations leucaena seems to have matched vetiver's soil-stopping abilities, but the shrubs had to be constantly cut back and maintained in the form of a thick, dense, contiguous hedge. In one trial in India where both were left almost untouched, soil losses through thick leucaena hedges were 15–16 tons per hectare, whereas the loss through (young) vetiver hedges was only 6 tons per hectare.
A decade ago, Thean Soo Tee began cultivating asparagus in the Mt. Kinabalu area of Sabah in his native Malaysia. He planted this Eurasian "shrub" some 1,200 m above sea level in hedges along the contours. The asparagus grew well and quickly on this irrigated land, maturing nine months after sowing. The plant's enormous root system held back the soil and saved the sloping fields from erosion.
Tee initiated this pioneering work years before the World Bank resuscitated the then moribund vetiver idea. His concern was to protect vegetable farms from erosion. With cabbage, peas, carrots, and other crops, the earth must be turned over after each harvest, exposing it to wind and water. Sabah's vegetable areas were turning into stone-strewn wastelands.
Tee recognized that because asparagus fetches a high price in the marketplace its cultivation would boost the income of local farmers. For his originality and endeavor, he earned a Rolex Award for Enterprise in 1984.17
This rugged, dense, leguminous shrub (Caragana arborenscens) is used in low shelterbelts and for erosion control in some of the coldest, driest, and most desolate areas of the American Great Plains. A nitrogen-fixing species from Siberia, it grows almost anywhere, but is best adapted to sandy soils. It can be successfully grown where annual precipitation is no more than 350 mm and where winter temperatures plunge to -40°C.