Sloping Agricultural Land Technology (SALT-1): A guide on how to farm your hilly land without losing your soil
Asia makes up less that one third (or 30%) of the total world land area and yet carries over half (56%) of the world's population. Moreover, the average population density of Asia becomes a significant long term problem when food production is considered. Some countries in Asia have up to 8 people per hectare in terms of population density. In addition, the Food and Agriculture Organization (FAO) of the United Nations predicts that the world have to double its food production by the year 2030 to feed its exploding population. However, Asia, when compared to the rest of the world, has very little land which is suitable for cultivation that has not already been exploited.
To compound the problem, much of the lands now under cultivation in Asia have been classified as degraded lands or lands that have already undergone moderate to severe erosion. According to FAG, many Asian countries now have 20% or more of their lands considered as "degraded" lands with some countries approaching 50% land degredation (sic).
One problem of the region is the rapid deplection (sic) of its forest cover. Mass deforestation for economic reasons is carried out in a reckless way. Shifting cultivators, due to population pressures, move into newly opened areas and begin to practice swidden (slash and burn) agriculture. Then the forest areas, which are generally fragile, sloping soils, are subjected to intensive agriculture practices which rapidly degrade the land.
The Philippine Experience
An example of what has happened in terms of deforestation and land degredation (sic) is what has taken place during one generation in the Philippines. The Philippines, one Asian country, has almost 30 million hectares. In the 1950's almost half of that (about 16 m ha) was classified as natural forest. Today, less than one million hectares of natural forest remains. In the same time period population has almost doubled and the marginal or "fragile" lands have increased from 2 million hectares to 12 million.
The greatest problem man will encounter when forest trees are cut extensively without replanting and improper farming of fragile, sloping lands is soil erosion. The erosion of the topsoil -that thin upper crust on the earth's surface on which man plants his food crops -is an extremely serious problem in Asia.
Importance of topsoil
Soil is the result of the gradual weathering of plants, rocks, and minerals. Soil formation is a very slow process that in some estimates takes place at the rate of 2.5 centimeters per century. Topsoil is rich and fertile because of its organic matter content. Plants and animals die, decay, disintegrate, and are incorporated in the soil, making the soil fertile and capable of supporting the growth of food crops.
Function of Topsoil
Topsoil stores plant nutrients, air, and moisture. It is a virtual factory of intense biological activity; innumerable fungi and bacteria in topsoil break down organic matter and make the soil richer. Topsoil, therefore, is essential to productive agriculture. The nutrients in topsoil are crucial to crop production. They are the food of plants. So if the topsoil is lost, you cannot get a good harvest from your land unless you use expensive commercial fertilizer. One best thing you can do, therefore, is to protect your hilly land from soil erosion. Bear in mind that poor soil makes a farmer poor and the land poor.
There are several traditional ways of controlling soil erosion, such as reforestation, terracing, multiple cropping, contouring, and cover cropping. The Asian Rural Life Development Foundation (ARLDF) in Kinuskusan, Bansalan, Davao del Sur, Philippines, promotes an erosion control technique that is both easier and less expensive to implement than the traditional methods. This technology is known as SALT or Sloping Agricultural Land Technology.
The SALT System
SALT is a package technology on soil conservation and food production, integrating different soil conservation measures in just one setting. Basically, SALT is a method of growing field and permanent crops in 3-meter to 5-meter-wide bands between contoured rows of nitrogen fixing trees. The nitrogen fixing trees are thickly planted in double rows to make hedgerows. When a hedge is 1.5 to 2 meters tall, it is cut down to about 75 centimeters and the cuttings (tops) are placed in alley-ways to serve as organic fertilizers.
SALT: An Agroforestry Scheme
SALT is a diversified farming system which can be considered agroforestry since rows of permanent shrubs like coffee, cacao, citrus and other fruit trees are dispersed throughout the farm plot. The strips not occupied by permanent crops, however, are planted alternately to cereals (corn, upland rice, sorghum, etc.) or other crops (sweet potato, melon, pineapple, castor bean, etc.) and legumes (soybean, mung bean, peanut, etc.). This cyclical cropping provides the farmer some harvest throughout the year. SALT also includes planting of trees for timber and firewood on surrounding boundaries. Examples of tree species for "boundary forestry" in SALT are mahoganies, casuarinas, sesbanias, cashew nuts, pili nuts, etc.
History of SALT
SALT was developed on a marginal site in Kinuskusan, Bansalan, Davao del Sur by the Mindanao Baptist Rural Life Center (MBRLC). In 1971, MBRLC started to employ contour terraces in its sloping areas. Dialogues with local upland farmers acquainted the Center with farm problems and needs which gave the Center the impetus to work out a relevant and appropriate upland farming system.
From testing different intercropping schemes and observing ipil-ipil-based farming systems in Hawaii and at the Center, the SALT was finally verified and completed in 1978. While it was still in the developing stage, the following guidelines were considered essential. The system must:
- adequately control soil erosion,
- help restore soil structure and fertility,
- be efficient in food crop production,
- be applicable to at least 50 percent of hillside farms,
- be easily duplicated by upland farmers with the use of local resources and preferably without making loans,
- be culturally acceptable,
- have the small farmer as the focus and food production as the top priority,
- be workable in a relatively short time,
- require minimal labor, and
- be economically feasible.
In 1978 a hectare of land was selected as a test site at the Mindanao Baptist Rural Life Center. It was typical of the surrounding farms: slope steeper than 15 degrees, had been farmed for five years or more, and had soils similar to those of most farms in the area. Contour lines were established carefully with the aid of an A-frame and planting of hedgerows and permanent crops was begun.
Advantages of SALT
The advantages of SALT are that it is a simple, applicable, low-cost, and timely method of farming uplands. It is a technology developed for Asian farmers with few tools, little capital, and little learning in agriculture. Contour lines are run by using an A-frame transit that any farmer can learn to make and use. A farmer can grow varieties of crops he is familiar with and old farming patterns can be utilized in the SALT system.
If farmers leave the SALT farm, like some tribal groups do, the nitrogen fixing trees and shrubs (NFTS) will continue to grow and overshadow the crop area. By the time the land is reverted to cultivation, the soil has been enriched already by the large amount of NFTS leaves and there is no erosion to contend with. In addition, the trees may be harvested for firewood or charcoal.
Various Forms of SALT
There are several forms of SALT, and a farmer may wish to use the SALT system in several variations. Simple Agro-Livestock Land Technology (SALT 2), Sustainable Agroforest Land Technology (SALT 3) and Small Agrofruit Livelihood Technology (SALT 4) are three variations of SALT that have been developed at the Mindanao Baptist Rural Life Center.
SALT 2 (Simple Agro-Livestock Land Technology) is a small livestock-based agroforestry preferably dairy goats with a land use of 40% for agriculture, 20% for forestry and 40% for livestock. As in a conventional SALT project, hedgerows of different nitrogen fixing trees and shrubs are established on the contour lines. The manure from the animals is utilized as fertilizer both for agricultural crops and the forage crops.
SALT 3 (Sustainable Agroforest Land Technology) is a cropping system in which a farmer can incorporate food production, fruit production, and forest trees that can be marketed. The farmer first develops a conventional SALT project to produce food for his family and possibly food for livestock. On another area of land he can plant fruit trees such as rambutan, durian, and lanzones between the contour lines. The plants in the hedgerows will be cut and piled around the fruit trees for fertilizer and soil conservation purposes. A small forest of about one hectare will be developed in which trees of different species may be grown for firewood and charcoal for short-range production. Other species that would produce wood and building materials may be grown for medium and long-range production. Other species that would produce wood and building materials may be grown for medium and long-range production. In some areas where the soil is too steep for row crops, contour lines may be established two or three meters apart and planted with flemingia or some other hedgerow species, and in between the hedgerows coffee, cacao, calamansi or other permanent crops could be planted.
SALT 4 (Small Agrofruit Livelihood Technology) is based on half-a-hectare of sloping land with 2/3 devoted to fruit trees and 1/3 intended for food crops. Hedgerows of different nitrogen-fixing trees and shrubs (Flemingia macrophylla, Desmodium rensonii, and Gliricidia sepium, etc.) are planted along the contours of the farm.
THE TEN STEPS OF SLOPING AGRICULTURAL LAND TECHNOLOGY (SALT 1)
Step 1: MAKE AN A-FRAME
Making the A-frame
In SALT, the first step you need to do is to make an instrument to locate the contour lines of your field. The ARLDF recommends using an A-frame. This is a simple yet effective tool which looks like the letter A, thus its name.
The A-frame is so simple that you make your own using materials generally found in your farm. To make the A-frame, three sturdy wooden or bamboo poles, a saw or bol, an ordinary carpenter's level, and string or rope are needed. Cut two pieces of wood at least one meter long to serve as the legs of the A-frame. Cut the third piece at least one-half meter long to be used as the crossbar of the frame.
Assembling the A-frame
Tie together the upper ends of the longer poles. Let the lower ends of the legs stand on level ground. Spread the legs about one meter apart to form a perfect angle. Brace horizontally teh shorter pole to become a crossbar between the two legs. Tie the carpenter's level on top of the crossbar.
Use of A-frame
Use the A-frame to find the contour lines of the land. Soil erosion can be prevented by plowing and planting following the contour lines. The contour line is a level line from one end of the field to the other and is found around the hill or mountain.
Other instruments for finding contour lines
Many other instruments can be used to find the contour lines of your field. One is the variation of the A-frame mentioned earlier which uses a string and a rock as a plumb-bob instead of the carpenters level. When done right, this is possibly the most simplest, economic and accurate method of locating contour lines.
Other farmers ahve chosen to use "O-rings", water levels, homemade transits and even professional transits themselves to locate the contour lines. Your method of locating the contour lines should be one that is acceptable to your local area.
Step 2: LOCATE THE CONTOUR LINES
Finding the Contour Lines
The next step is to use your instrument of choice to locate the contour lines in your field. Cut tall grasses or remove any obstructions so that you can move easily and mark lines. When using the A-frame, two people will make the work much easier and faster. One will operate the A-frame while the other marks the located contour lines with stakes.
Make a study of the area for which contour lines are to be determined. Begin marking contour lines near the highest point. Let the A-frame stand on the ground. Without moving the rear leg, lift the front leg. Then put the from leg down onthe ground that is on the same level with the rear leg.
The two legs of the A-frame are on the same level when the air space in the carpenter's level stops in the middle. When this happens, it means that you have found the contour line which is a level line between the two legs of the A-frame. Mark with a stake the spot where the rear leg stands.
Length of Contour Lines
Move the A-frame forward by placing the rear leg on the spot where the front leg stood before. Adjust the front leg again until it levels with the rear leg. For every two to three meters of contour line you find mark it with a stake. Follow this procedure until you reach the entire length of the contour line which is the other side of the mountain or hill.
Distance of Contour Lines
Try to locate as many contour lines as possible. Remember, the closer the contour lines to each other, the more potential erosion control occurs. Also, more nutrient rich biomass is produced and made available to the crops growing in the alley.
There are two criteria for determining the distance between contour lines: vertical drop and surface distance. Generally, no more than a one meter vertical drop is desirable for effective erosion control. Therefore, the steeper the slope, the closer the contour hedgerows. Conversely, the flatter the slope, the wider the spacing of hedges. However on the flatter slopes, it is recommended that contour hedgerows be spaced no further apart than 5 meters in order to maximize the benefits of the nitrogen fixing trees/shrubs on soil fertility management.
In determining a one meter vertical drop, the "eye-hand" method is a simple procedure to use. If using a transit or home-made transit, the 1 meter vertical drop can be obtained very quickly.
Step 3: PREPARE THE CONTOUR LINES
After you have found and marked the contour lines, prepare them by plowing and harrowing until ready for planting. The width of each area to be prepared should be one meter. The stakes will serve as your guide during plowing.
Step 4: PLANT SEEDS OF NITROGEN FIXING TREES AND SHRUBS
Planting Nitrogen Fixing Species
On each prepared contour line make two (2) furrows at a distance of one-half meter apart. Sow the seeds in each furrow to allow for a good, thick stand of seedling. Cover the seeds lightly and firmly with soil.
Importance of Leguminous Hedgerows
The ability of nitrogen fixing trees to grow on poor soils and in areas with long dry seasons makes them good plants for restoring forest cover to watersheds, slopes and other lands that have been denuded of trees. Through natural leaf drop they enrich and fertilize the soil. In addition, they compete vigorously with coarse grasses, a common feature of many degraded areas that have been deforested or depleted by excessive agriculture.
Examples of Nitrogen Fixing Trees and Shrubs (NFTS)
Flemingia macrophylla, Desmodium rensonii, Gliricidia sepium, and Calliandra calothyrsus are the best examples of nitrogen fixing trees for hedgerows on the SALT farm. Other examples of nitrogen fixing trees and shrubs (NFTS) which may be suitable for SALT hedgerows are Indigofera tyesmane, Calliandra tetragona, Leucaena luecocephala, and Leucaena diversifolia. The members of the Cassia genus such as spectabilis and siamea are not mentioned here because of their doubtful fixing on nitrogen. Remember, you must select the species that grows best in your climate and particular soils.
Step 5: CULTIVATE ALTERNATE STRIPS
The space of land between the thick rows of nitrogen fixing trees where the crops are planted is called a strip. Others names for the strip are alleyways or avenues.
Cultivating Alternate Strips
If you wish to prepare the soil for planting before the NFTS are fully grown, do it alternately, on strips 2, 4, 6, 8 and so on. Alternate cultivation will prevent erosion because the unplowed strips will hold the soil in place. When the NFTS are fully grown, you can proceed with cultivation on every strip.
Step 6: PLANT PERMANENT CROPS
Plant permanent crops in every third strips. They may be planted at the same time the seeds of nitrogen fixing trees are sown. Only the spots for planting are cleared and dug; later, only ring weeding is employed until the NFTS are large enough to hold the soil so full cultivation can begin.
Examples of Permanent Crops
Durian, lanzones, rambutan, 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 while the short ones are planted at the top. Shade-tolerant permanent crops can be intercropped with the tall crops.
Step 7: PLANT SHORT-AND-MEDIUM TERM CROPS
You can plant short and medium-term income producing crops between stripc of and among permanent crops. They are your sources of food and regular income while waiting for the permanent crops to bear fruits.
Examples of Short-term Crops
Suggested short and medium-term crops are pineapple, ginger, gabi, castor bean, camote, peanut, mung bean, sorghum, corn, upland rice, etc. To avoid shading, short plants are planted away from tall ones.
Step 8: TRIM REGULARLY NITROGEN FIXING TREES/SHRUBS
About once a month, the continuously NFTS are cut down to a height of one to one half meters from the ground. Cut leaves and twigs are always piled at the base of the crops. They serve as a soil cover to minmize the impact of the raindrop on the bare soil. They also act as an excellent organic fertilizer for both the permanent and short-term crops. In this way only, a minimal amount of commercial fertilizer (about 1/4 of the total fertilizer requirements) is necessary.
Step 9: PRACTICE CROP ROTATION
Rotating Non-Permanent Crops
A good way of rotating is to plant grains (corn, upland rice, sorghum, etc.), tubers (camote, cassava, gabi, etc.) andothe rcrops (pineapple, casto bean, etc.) on strips where legumes (mung bean, bush sitao, peanut, etc.) were planted previously and vice versa. This practice will help maintain the fertility and good condition of your soil. Other management practices in crop growing like weeding and pest and insect control should done regularly.
Step 10: BUILD GREEN TERRACES
Maintain Green Terraces
Apart from providing you with adequate food and sufficient income, another even more important benefit of using SALT is the control of soil erosion. This is done by the double thick rows of nitrogen fixing trees and ht natural terraces being formed along the contour lines. As you go on farming the sloping land, keep gathering and piliing up straw, stalks, twigs, branches, leaves, rocks, and stones at he base ofhte rows of nitrogen fixing trees. By doing this regualrly and as the years go by, you can build strong,sustainable, naturally green and beautiful terraces which will reliable anchor your precious soil in its right place.
Advantages of SALT Farming
As a proven system of upland farming, SALT has certain good qualities over both the tradtional techniques of slash-and-burn and conventional terrace farming.
- The SALT system protects the soil from erosion.
- SALT helps restore soil fertility and structure.
- SALT is efficeint in food crop production.
- SLAT is applicable to at least 50 per cent of hillside farms.
- SALT can be duplicated readily by hillside farmers.
- SALT is culturally acceptable becaused the farming production as the top priority. Fruit trees, forest and other crops are secondary priority.
- SALT is workable in a relatively short time.
- SALT is economically feasible.
- SALT is ecologically sound.
- The SALT farm can easily revert back to forest land if left unfarmed.
- In the Philippines SALT fits into the framework of the government's rainfed resoiurces development strategy for the uplands.
The Asian Rural Life Development Foundation recognizes that SALT is not a perfect farming system. There is not and never will be one system for all farmers. SALT is not a miracle nor a panacea. To establish a one-hectare SALT farm requires much hard work and discipline. There is no easy way. It takes three to ten years to deplete the soil of nutrients and to lose the topsoil; no system can bring depleted, eroded soil back into production in a few short years. Soil loss leads to low yields and poverty, but land can be restored to a reasonable level of productivity by using SALT.
Source: Asian Rural Life Development Foundation Editorial Staff, 1997. How to Series (1), Kinuskusan, Bansalan, Davao del Sur, 20p.