Cultivation of Trees and Crops for Sustainable Use of Sloping Lands
Planting Trees
Various species of the tree of crocodile fern are planted along contour lines near the tops of hills. If the land is fairly fertile, the following kinds of tree might be selected because of their economic value: anise, cinnamon, chitagong, chick-rassay(Chukrasia tabularis), and champac (Michelia medicris). Bamboo may also be a high-value crop. If the land is low in fertility, the following kinds of tree might be selected which will produce timber and improve the soil: various species of Acacia (Acacia auriculiformis, A. mangium) and kassod tree (Senna siamea). Alternate planting of deciduous trees (kassod tree etc.) and conifers (pine trees etc.) is also possible. Some kind of agro-forestry is recommended while the trees are still small and the canopy of the trees is still open. Domestic animals such as goats and cows may be raised under the canopy. The trees will supply families with fuel and other agricultural products. They will offer good grazing for cattle. But most important, they will conserve water resources and protect land from degradation.
Band Cultivation of Trees and Crops
Band cultivation of trees and crops (greening band) protects land from erosion, increases the fertility of soil, and provides green manure and fodder (Fig. 1).
Leguminous trees or crops are recommended, such as white tephrasia (Tephrosia candida), leucaena (Leucaena leucocephala), and pigeon pea (Cajanus cajan). The optimum distance between bands is from 5 to10 m, depending on the gradient of the slope. The width of each band is usually about 1m. Before planting, soil in the band should be well ploughed for better seed germination and better growth of plants.
Crop Cultivation in between Greening Bands
The space between greening bands above mentioned can be used for crops. Any kind of annual or perennial crop can be planted. Annual crops may include upland rice, maize, sorghum, millet, cassava, peanut and sesame. Examples of perennial crops include tea and cocoa.
In the case of annual crops, it is recommended to rotate crops each year so as to prevent the build-up of pests specific to each crop. Rotation will also help maintain soil fertility.
In the dry season, cut branches of trees planted in the greening band can be used for mulching the adjacent fields. Mulching will sustain soil moisture, enrich the soil, and prevent erosion.
Cultivation of Fruit Trees
Fruit trees are usually grown at the foot of hills. This is because fruit trees need a lot of care, and fairly fertile soil. Grafted fruit trees are recommended rather than layered trees. This is because grafted trees are generally more vigorous in rooting than layered ones. The applica-tion of fertilizer, and the control of pests and diseases, are recommended for better yield. The kinds of fruit trees should be chosen carefully, according to the local environmental conditions and market demand.
Index of Images
Figure 1 Diagram of <I>Greening Bands</I> Planted along Contours, with Crops between the Bands
Figure 2 Double Hedgerow of Leguminous Shrubs (<I>Desmodium Rensonii</I> and <I> Calliandra Callothyrus</I>)
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