Saltby Ross Mittleman

As the global population continues to explode at an exponential rate the encroaching pressures upon agricultural lands and those who work them are being felt in an increasingly intense manner. Those pressures have been highlighted ever since the emergence of the Green Revolution sought to usher in a new era of intensive farming designed to bring about a surplus supply that could keep pace with a rapidly burgeoning demand. Currently, every type of effort is made to increase yield on a given parcel. Additionally, traditional definitions of what constitutes arable land are being abandoned for a new type of criteria that includes even the most marginalized terrain as a potential site for cultivation.  From small urban plots to irrigated farms of the arid southwestern U.S. far from the source of that water, previous lands deemed inhospitable to agricultural production are undergoing reevaluation with a new and more urgent perspective. Those of us who inhabit the United States envision most farmland gently rolling along a flat vast expanse of earth. However, in many other parts of the world farmers look at a hillside and envision crops clinging to a steep gradient because that is the only choice they have.  The challenges associated with mountain farming are numerous and become exacerbated by climatic conditions, particularly tropical ones. Enter SALT, Sloping Agricultural Land Technology, a strategy pioneered in the Davao region of the Philippines that has gained notoriety and accrued devout practitioners in areas with mountainous terrain throughout the world.

As the name indicates, SALT offers approaches and techniques for those working lands with varied topographic relief. The objectives are both agricultural and environmental as the technology aims to increase production over the long term while eliminating erosion and land degradation. A man named Harold Watson pioneered the idea while working in the Davao del Sur province of the Philippines during the early 1970’s.  A Baptist missionary from Mississippi, Watson began to recognize the need for a more sustainable form of farming in the region after several years of observation and hands on experience working with the locals. The dominant trend at the time was a type of slash and burn, or swidden, agriculture still practiced throughout much of the developing world where native vegetation is first cut to the ground and later burned when dry. This practice gives soils a one-time injection of nutrients from the ashes that can be readily taken up by crops planted the following season, usually corn or soy. By denuding the land of native vegetation in place of annual crops the potential for rapid degradation and erosion increases exponentially. Without proper crop rotation whatever soil remaining is rendered unproductive and generally abandoned within three to four years. In tropical areas like the Philippines, heavy monsoon rains falling on hillsides cause massive amounts of erosion, loss of nutrient-rich topsoil, and even landslides with disastrous results. These abandoned plots are the most susceptible to extreme environmental factors that trigger chain reactions felt from the top of a valley to the rivers below that become over-run with sediment.

Forestry and Agriculture ComponetsThrough observation, experimentation, and innovation, Watson and his companions at Mindanao Baptist Rural Life Center set about finding more sustainable solutions. They identified a number of nitrogen fixing trees that when planted stabilized areas prone to erosion, enhanced the quality of the soil, and when pruned the cuttings can be used for mulch and livestock fodder. (further reducing exposed earth) These trees, such as gliricidia sepium or leucana (commonly referred to by the natives as ipil ipil) were first planted along a contour of the sloping area in three to five meter wide bands. The contour was determined through a basic wooden A-frame tool with a rock tied to a string that hung in the middle. By working this contraption across a hillside, and using the laws of triangulation, a line level at a specific elevation could be marked out and planting could commence. Once the trees were established, famers planted rows of perennial crops such as coffee, banana or cacao. Yet another category of annual crops such as beans, cucumbers, eggplant, peanut, or tobacco are sown between the established hedgerows up and down the slope. If crops were rotated appropriately throughout the seasons erosion was drastically reduced while soil fertility was greatly enhanced, resulting in increased yields.

This system rapidly gained favor and went from a small-scale regional experiment to a widely accepted method. Others have championed the cause throughout the world including Ray Wijewardene, a British agricultural engineer (as well as an accomplished aviator, businessman, inventor, and gold-medal winning sailor) who is credited with bringing the technology to other parts of Asia and Africa and customizing the systems to each individual climate and culture. Ray further advanced SALT by heavily stressing the need for all soil within the system to be cloaked by vegetative matter, in the form of living plants or mulch. He further expanded upon Watson’s original ideas by stressing the importance of incorporating  a perennial polyculture. The result was a new type of agroforestry combining the benefits of seasonal crop production with sustained harvest of natural materials in the form of firewood and livestock fodder. The emphasis on agroforestry accomplished two other functions in regards to weed control, a major challenge in tropical agriculture. One, as mentioned above, was the introduction of leaf litter that suppresses weed growth. The second factor had to do with a limited canopy that allowed some shading for crops that do not require constant direct sunlight, and further limited weed germination rates.

Wijewardene was highly instrumental in promoting SALT throughout other regions of Asia beyond the Philippines, but the Mindanao Baptist Rural Life Center (in cooperation with its sister partner the Asian Rural Life Center) are the ones truly credited with developing and spreading its message to this day. What stands out about these organizations is a full-fledged commitment to communities in which they are designed to serve. SALTWhere as many NGO’s this day in age struggle to connect with the people they hope to help, the MBRLC and the ARLC work lock-step with locals in the region. Harold Watson had the foresight and patience during the initial development of SALT to listen to the problems facing farmers and offered a calculated comprehensive response tailored to their specific needs. He built a consensus at the ground level and began attracting participants in a deliberate manner. He used religion as a tool to strengthen and unify the community.  It was also a philosophy based on education that continues to anchor the foundation of the current incarnation of the MBRLC. People come from the tropical highlands of Guatemala, the Hindu-Kush Himalayas, and West Africa to learn these innovative techniques and bring them home. Adaptations of SALT have sprung up world wide, including the advent of keyline contouring practiced throughout much of Australia, which utilizes contour topography to trap rain water and lessen run-off. With SALT, the grass-roots movement has gained traction within the government as several bills have recently gone before congress to set up national standards and financing. The bottom up approach has proven highly effective in attracting even the most skeptical farmers as they begin to see positive results for those adopting the methods. The movement inspires a second look at the sheer variety and adaptability of agriculture to take shape and form where least expected, and raises the question…where else?



Sources for material and information used in this article:

A good resource for farmers looking to employ SALT principles: