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You are here: Home Magazines Global edition Mountain agriculture SALT: Sloping Agricultural Land Technology

SALT: Sloping Agricultural Land Technology

Written by Henry lito D. Tacio last modified Jun 15, 2011 02:30 PM

Chemical fertilizers, very popular because they 'miraculously' increase crop yields may yet prove to be man's undoing. Agricultural scientists have shown that continued use of only chemical fertilizers causes soil organisms to die. Without soil organisms, chemically saturated land will eventually lose its capacity to nourish healthy and fruitful crops, until finally the soil 'dies' a natural death. With 'dead' soil, how can man grow his food to feed himself?

ILEIA Newsletter • 4 nº 1 • March 1988

Alley cropping along the contourlines. Photo: SALT.‘We are facing not merely a vexing problem’, says a noted agriculturist. ‘We are facing certain destruction and even death if we continue to destroy the natural resources that support life on earth.’ In the Philippines, sixty percent of the total land area of 30 million hectares is upland with a population of 1.5 million (Serrano, 1984). It is a common knowledge among Filipino people that these uplands are now bald, ugly and almost useless. ‘Poor soil makes a farmer poor’, says the Rev. Harold R. Watson, the director of the Mindanao Baptist Rural Life Centre, in Kinuskusan, Bansalan, Davao del Sur. ‘And poor farmers make a country poor.’

How to help the uplanders?

Poverty is indeed spreading wildly in the uplands of the Philippines. But can something be done to help improve the life of the uplanders? This is the question that worries the Rev. Harold Watson, an American agriculturist-missionary from the state of Mississippi, several years back. His biggest problem is how to stop soil erosion and restore -if already eroded- the fertility of the soil. ‘Soil erosion is an enemy to any nation - far worse than any outside enemy coming into a country and conquering it because it is an enemy you cannot see vividly’, the Rev. H. Watson remarks. ‘It's a slow, creeping enemy that soon possesses the land’. In the beginning, the Rev. H. Watson and his associates at the Centre tried many ways to stop the erosion and restore soil fertility. ‘None of our ideas really worked’, recalls the Rev. H. Watson. ‘We built terraces and these washed out. Information gathered from different agricultural universities and colleges did not work either’.


Fig. 1: Finding the Contour lines

The Leucaena tree, a discovery

In 1973, the Rev. Harold Watson, on furlough, went to Hawaii and there met Dr. James L. Brewbaker, who gave him a very small package of seeds of Leucaena leucocephala, collected by Dr. Brewbaker himself and his colleagues in Central America. The Rev. Mr Watson planted the Leucaena seeds at several locations on the Centre’s 19 hectares. As the Rev. Mr Watson and his associates struggled to hold up their terraces, it became evident that this could best be done with living trees and that the Leucaena as a nitrogen-fixing legume was a natural on all except the most acid soil sites. ‘We kept on experimenting’, the Rev. Mr I Watson recalls. ‘At first we planted one row of Leucaena. (But) if several trees did not grow so well, you had a hole in the dike for soil to wash through. We finally settled on planting two dense rows with seeds of Leucaena that had been soaked in water. The seeds are just dribbled in, maybe an inch apart, in two rows just half a meter apart. Two dense rows make a reliable hedge and the soil that washes off the slope can build up against the hedge to make the terrace’.


In 1978, the Rev. Harold Watson and his associates finally verified and completed the scheme and called it Sloping Agricultural Land Technology or SALT. SALT is a way of farming that can turn a sloping parcel of land into a highly productive upland farm. As a proven system of upland farming, SALT bas certain advantages over both the traditional techniques of slash-and-burn (swidden agriculture) and conventional terrace farming. SALT enables farmers to stabilize and enrich the soil and to grow food crops economically. There is also a reduced need for expensive inputs like chemical fertilizers.

In like manner, the SALT scheme is tailored for small family farms and for raising both annual food crops and permanent crops. Also, it is culturally acceptable because the farming techniques are in harmony with the beliefs and traditional practices of Filipino people. Furthermore, it has proven applicable to most of the regions throughout the Philippines. In addition, SALT also conserves soil moisture and reduces pests and diseases. Moreover, it replaces an ugly eroded hillside with a terraced and green landscape. But most important of all, to a financially harried farmer, the technology can increase his annual income to almost threefold after only a period of five years.

How to use SALT

SALT is a simple, applicable, low-cost but effective way of farming hilly lands without losing top soil to erosion. It consists of ten basic steps as discussed briefly below:

  1. Making the A-frame. The A-frame is a simple device for laying out contour lines across the slope. It is made of a spirit level and a three wooden or bamboo poles (two should be about one meter long each and one about one-half meter long) nailed or tied together in the shape of a capital letter A with a base of about 90 centimetres. The spirit level is mounted on the crossbar.
  2. Finding the contour lines. One leg of the A-frame is planted on the ground, then the other leg is swung until the spirit level shows that both legs are touching the ground on the same level. A helper drives a stake beside the frame's rear (first) leg. The same level finding process is repeated with stakes every 5- meter distance along the way until one complete contour line is laid out, and until the whole slope is covered. Each contour line is spaced from 4 to 6 meters apart for a steep hill, and 7 to 10 meters apart for a more gradual one.
  3. Cultivating the contour lines. One-meter strips along contour lines are ploughed and harrowed until ready for planting. The stakes serve as guide during ploughing.
  4. Plant nitrogen-fixing trees. On each prepared contour line, make two furrows one-half meter apart. Plant the seeds of leguminous trees like Leucaena leucocephala, Flemingia congesta, Leucaena diversifolia, Calliandra callothyrsus, or Sesbania grandiflora. Branches of Gliricidia sepium can also be used. One furrow can be planted with say, L. leucocephala, and other furrow with F. congesta. Always use a combination of various tree species to minimize the risks of pest attacks like e.g. by psyllids. The seeds are firmly covered with soil. Where time is of no importance, the trees can be left to grow until they are four to five meters high, which by then should form a shade that will kill the grasses and eliminate the need for cutting grasses.
  5. Planting the permanent crops. The space of the land between the thick double rows of nitrogen-fixing trees is called a strip, where the crops are planted. Permanent crops may be planted at the same time the seeds of leguminous trees are sown. Only the strips for planting are cleared and dug; and later, only ring weeding is employed until the nitrogen fixing trees are large enough to hold the soil for full cultivation to commence. Permanent crops are planted in one strip out of every four. This refers to strips 1, 4, 7, 10 and so on. Coffee, banana, citrus, cacao, and others of the same height are good examples of permanent crops. Tall crops are planted at the bottom of the hill and the shorter ones are planted at the top.
  6. Cultivating alternate strips. The soil can be cultivated even before the nitrogen-fixing trees are fully grown. Cultivation is done on alternate strips, on strips 2, 5, 8 and so on. The uncultivated strips collect the soil that erodes from higher cultivated strips. When the nitrogen-fixing trees are fully grown, every strip can be cultivated.
  7. Planting the short-term crops. Short- and medium-term income producing crops are planted between strips of permanent crops as source of food and regular income, while waiting for the permanent crops to bear fruit. Suggested crops are pineapple, ginger, sweet potato, peanuts, sorghum, corn, melons, squash, and up land rice, etc.
  8. Trimming the nitrogen-fixing trees. Once a month, the continuously growing nitrogen-fixing trees are cut down at a height of one meter from the ground. Cut nitrogen-fixing leaves and twigs are always piled at the base of the crops. They serve as an excellent organic fertilizer for the plants. In this way, only minimal amounts of commercial fertiliser, if any, are necessary.
  9. Management. The non-permanent crops are always rotated to maintain productivity, fertility and good soil formation. A good way of doing this is to plant grains (sorghum, corn, upland rice, etc.), tubers (sweet potato, cassava, etc.) and other crops (pineapple, squash, melons, etc.) in strips where legumes (beans, peanuts, pulses, etc.) were planted previously and vice versa. Other crop management practices such as weeding, insect and weed control, are also done regularly.
  10. Building green terraces. To enrich the soil and effectively control erosion, straws, stalks, twigs, branches, leaves, rocks and stones are piled at the base of the thick rows of nitrogen-fixing trees. As the years go by, strong, permanent and naturally green terraces will be formed which hold the soil in place.

National and international interest

A number of agricultural colleges and universities in the Philippines are putting up their own SALT farms under the Agricultural Education Outreach Project (AEOP) which is receiving financial support from the United States Agency for International Development (USAID). Upland development researchers and scientists from Indonesia, India, Sri Lanka, Korea, Bangladesh, New Guinea, Kenya, Liberia, the Solomon Islands, Taiwan, Ghana, Thailand, Australia and Japan, among many others, have visited the hillside demonstration farm in Bansalan, Davao del Sur, for possible adoption of the technology in their countries. To satisfy the mounting interest of the public in SALT, the Mindanao Baptist Rural Life Centre has designed an extensive training and extension program for the technology. An illustrated manual and flip chart have been produced showing the detailed steps in the establishment and maintenance of a SALT farm. Readers who wish to know more about the upland technology may writ to the Rev. Harold R. Watson at Mindanao Baptist Rural Life Centre, P.O. Box 94, Davao City, Philippines.

Henry D. Tacio is a contributing editor of AGRISCOPE Magazine / Philippines, and is presently working as Staff Writer of Mindanao Baptist Rural Life Centre in Kinuskusan, Bansalan, Davao del Sur, Philippines.

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