For further information contact: Reinhardt Howeler

[Vetiver-grass Contour Hedgerows] [Paspalum atratum hedgerows] [Tephrosia Candida Hedgerows] [Hedgerows of either Gliricidia sepium or Leucaena leucocephala] [Intercropping] [Balanced Fertilizer Applications]

Vetiver-grass Contour Hedgerows

Farmers start by setting out contour lines in their field, using either an A-frame (made with locally available materials), a line level (adapted from a cheap carpenter’s level, so it will hang on a string), or a hand-held level (available at about US$40), useful for extension agents or groups of farmers working in larger fields. Using a hoe or similar tool, farmers make a shallow ditch along the contour line. Vetiver-grass plantlets are then planted in the ditch at about 10 cm between plants. The ditch is filled in around the roots and the soil pressed down to provide good contact between roots and surrounding soil. Adequate rainfall or initial watering is essential for adequate establishment.

Once well established, vetiver grass is highly drought tolerant and requires minimum maintenance. To enhance tillering and provide mulch to spread on the surrounding soil (a very effective erosion control practice in itself), the grass should be cut back regularly at about 30 cm above the ground. The grass will withstand burning and is not damaged by hungry buffaloes. Vetiver grass can be propagated by separating the tillers of a mature mother plant, cutting back the tops and roots to about 10-15 cm each, and planting them either directly in the field or in small plastic bags filled with soil and kept for several weeks in the nursery. Most vetiver-grass ecotypes do not produce viable seed and the grass will not spread either by seed or stolons to become a weed. Thai cassava farmers tend to prefer this method of erosion control.

Paspalum atratum hedgerows

This grass is similar to vetiver grass in that it has an erect plant type and is nearly as effective as vetiver grass in reducing erosion when planted along contour lines. The grass thrives best under humid conditions, but will survive the dry season reasonably well. The main advantages of Paspalum atratum are its capacity to reproduce vegetatively (tillers) or by seed. The latter method substantially reduces establishment costs. The small seed is dribbled into very shallow (2-3 mm deep) contour lines and lightly covered with soil. Good soil moisture is essential for germination. The second advantage is that this grass is highly palatable and is a good cut-and-carry grass for feeding cattle, buffalos, fish, and even pigs. The grass’s major disadvantage, however, is that hungry buffaloes can damage the hedgerows during the dry season. South Vietnamese cassava farmers mostly prefer this method of erosion control, as they usually also raise cattle.

Tephrosia Candida Hedgerows

This leguminous shrub is well adapted to subtropical climates with cold winters and to very acid, low-fertility soils. It also tolerates long droughts. It is easily planted by dropping seed into shallow contour lines and covering with soil. The plants are usually cut back to about 40 cm above the ground when cassava is planted. The cut stems and leaves are incorporated into the surrounding soil or spread as mulch. North Vietnamese farmers like this method because the leaves add organic matter and N to the soil, the hedgerows are easily and cheaply established from seed, and, after 3-4 years, the stems of old plants can be used as firewood. At that stage, the hedgerows will need to be replanted or the terrace risers that have formed left with native weeds. Although T. candida seeds prolifically during winter, for good seed production the plants must be sprayed for protection against pod-boring insects.

Hedgerows of either Gliricidia sepium or Leucaena leucocephala

These medium-height, leguminous shrubs produce leaves high in crude protein that can be used as feed for farm animals during the dry season or as green manure when spread out on or incorporated into the soil. Gliricidia can be planted either from stem cuttings or from seed; the latter being preferred when used as a contour hedgerow for erosion control. Leucaena is a prolific seeder and is always planted from seed. This latter species prefers high Ca soils and is not well adapted to very acid soils. Farmers of East Java, Indonesia, prefer these species as they can use the leaves as animal feed during the dry season. These hedgerows are not as effective as the grass hedgerows in reducing erosion, but they do contribute to natural terrace formation, which is itself an erosion control measure.

Intercropping

In Vietnam, many small farmers intercrop cassava, mainly with peanut.  Peanut is planted either 2-3 weeks before cassava, especially in areas with a cold spring, or at the same time as cassava. Usually one or two rows of peanut are planted between rows of cassava, which are spaced at 0.8-1 m. The peanut is harvested 3½-4 months after planting and before they compete too much with cassava. The peanut protects the soil from rainfall splash and erosion, and this crop’s residues, when incorporated, contribute organic matter and N to the soil. This system usually increases the farmer’s total income, as compared to planting cassava as a monocrop.

Balanced Fertilizer Applications

Balanced applications of fertilizers will markedly increase early plant growth and thus provide a more rapid and more effective canopy to protect the soil from rainfall splash and erosion. Fertilizer application is thus a highly effective way of reducing erosion while increasing yields. What constitutes balanced fertilizer application depends on the native soil fertility and the availability and cost of alternative nutrient sources. Ideally, it consists of a combination of animal manure and chemical fertilizers high in N and K, as described under Fertility Maintenance.