Farming the hillsides
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CTA. 1994. Farming the hillsides. Spore 51. CTA, Wageningen, The Netherlands.
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No one cultivates sloping land out of choice: hillsides are difficult to cultivate, especially with animals or tractors, and they are notoriously prone to water and soil erosion. To reduce or prevent erosion on steep slopes, where simply cultivating...
No one cultivates sloping land out of choice: hillsides are difficult to cultivate, especially with animals or tractors, and they are notoriously prone to water and soil erosion. To reduce or prevent erosion on steep slopes, where simply cultivating along the contour is not sufficient, construction of terraces has been a necessity. Not surprisingly farmers have often avoided, or tried to circumvent, the very considerable labour requirement of terrace construction and erosion has been the inevitable consequence. The alternative of a biological terrace-building system offers a minimum labour option to farmers on steep sloping land. The biological system of making terraces on steep land has been developed in Asia (Philippines, Nepal and Sri Lanka) and is applicable wherever there is adequate seasonal rainfall to support shrubby tree species such as acacia, leucaena, gliricidia and caliandra. Known as SALT - Sloping Agricultural Land Technology, it offers a promising minimum labour cost option for erosion control and land stabilization in moister areas of ACP countries where population pressure has forced cultivators to clear and crop hillsides. The objectives of SALT are threefold: to control erosion, to help restore soil structure and fertility, and to produce food efficiently. Other mechanical soil conservation measures not only require considerable labour and/or mechanization inputs for their construction but also for their maintenance. Moreover, while they control erosion they do not contribute to restoration of soil structure and fertility, and stone terraces and lock and spill drains usually require some land to be taken out of production. SALT is essentially a hedgerow agroforestry system, where leguminous fast-growing species are planted along the contour to trap soil washed downhill. Two rows of trees are plated one meter apart and the space between may be filled with stones. As the trees grow they provide a natural barrier to soil movement. The double row hedges are planted four to six metres apart and the intervening land is stabilized for cropping. Between the hedgerows the recommendation is to plant a combination of permanent, semi-permanent and annual crops. Crop combinations will vary according to local conditions and preferences but they should be chosen to enhance soil fertility, maximize yields, and allow farmers to have an efficient work schedule throughout the year. Two out of three 'alleys' (inter-hedgerow spaces) may be planted to annual crops and the third to permanent cash crops such as cocoa, coffee, tea, banana, citrus, other fruit or spices. In the annual crop alleys normal weeding and pest control should be done as normally practiced but in the permanent crop alleys weeding should be confined to spot treatment around the young plants until the hedgerow trees themselves have grown large enough to hold the soil in place. This permanent cropping across a further one third of the hillside acts as an additional barrier to soil movement. One refinement is that a fast growing grass species, which has a strong root system, may be planted in a narrow strip immediately below each hedgerow. The grass provides additional soil stabilization, especially in the early stages of hedgerow establishment. Also, the grass may be cut regularly for livestock fodder and to provide mulch and organic matter for the annual crop land. Hedgerows are also cut to provide livestock feed and for mulching bare soil and their foliage contributes nutrients to the soil. The ideal height for pruning is when the hedgerows are two metres high; they should be cut back to 50 cm to encourage vigorous coppice re-growth. In recent years the 'Fanya ju' terracing system developed in Kenya has received considerable publicity and there is occasionally confusion between the Fanya ju and SALT systems. The two systems are, however, quite distinct and have been contrasted for Spore by Dr M R Rao of the International Centre for Agroforesty, (ICRAF), Nairobi. 'Fanya ju and SALT are different. 'Fanya ju' is a mechanically established system where a ditch is dug along a contour and the soil is thrown to the up-slope side so as to form a bank (bund). 'Fanya ju' has been used mostly in Kenya. It might appear in other East African countries but not, to my knowledge, in the Caribbean or elsewhere. 'Fanya chin)' is its counterpart because the soil dug from the ditch is thrown to the down-slope. 'Fanya ju' can be turned into an agroforestry system by planting trees on the bund or in the ditch. Usually grasses are allowed to grow on the bund stabilizing it. Fruit trees are often planted in the ditch because the soil is damper there than on the rest of the terrace and fertility is enhanced by litter and other debris. 'Fanya ju' is a labour intensive system to construct and takes quite a bit of land out of production. Some of these areas can be recouped if trees and appropriate shrubs are planted on the bunds or in the ditches. Conversely, all SALT techniques employ agroforestry methods right from the start. They rely greatly upon biological means to conserve the soil and improve its fertility with minimal labour input. The amount of land wasted, as compared with 'Fanya ju', is also reduced.' Futher information on the SALT system may be obtained from: Mindano Baptist Rural Center PO Box 94, Davao City 8000 THE PHILIPPINES.
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