Providing an Alternative to Slash and Burn Agriculture
“Making serious change is a very time consuming and costly business.”
– Mike Hands, founder of the Inga Foundation.
The village of Gaviotas, situated in the llanos region of Colombia, is cited as one of the premier examples of the development and implementation of place-based, appropriate technology. The term appropriate technology is often used to describe technological innovation or devices that are affordable enough to be considered for widespread use in the developing world. What we often forget when discussing such advances is that technology doesn’t always mean gadgets, especially when talking about ways to improve the bottom line of life in the most impoverished places on the planet. Agriculture is one of the oldest sciences in the human experience, and technological advances in this field are one of the major influences that have allowed us to build, grow, and thrive in all other aspects of life over the last 10,000 years .
Some estimates show that upwards of 300 million farmers practice slash and burn agriculture in the world today. This occurs primarily in the equatorial regions that harbor the rainforests and has been taking place just as long as humans have been farming. Steif asserts, “When used properly, slash and burn agriculture provides communities with a source of food and income. Slash and burn allows for people to farm in places where it usually is not possible because of dense vegetation, soil infertility, low soil nutrient content, uncontrollable pests, or other reasons.” However, this mentality doesn’t take into account the world’s rapidly declining natural resources alongside of our rapidly increasing world population. The results of continuing on this path of slash and burn are massive deforestation, erosion, decreased biodiversity, nutrient loss, and possibly most significant is the huge net increase in global carbon emissions that result from slash and burn practices.
Estimates show that, depending on location, between 4800 and 6200 square miles of rainforest are cut down and burned every year to make way for agriculture in each region where slash and burn is practiced. A different study states that, “The loss of forests has a great effect on the global carbon cycle. From 1850 to 1990, deforestation worldwide released 122 billion metric tons of carbon into the atmosphere, with the current rate being between 1.6 billion metric tons per year (Skole et al. 1998). In comparison, all of the fossil fuels (coal, oil, and gas) burnt during a year release about 6 billion tons per year.”
Mike Hands, of The Inga Foundation, has committed decades of his life to researching and implementing a viable alternative to slash and burn agriculture. His approach doesn’t only combat the ecological ills of slash and burn.. The techniques developed during more than 15 years of scientific study can also contribute to both the short and long term prosperity of the human communities that implement Inga Alley Cropping. These innovations, pioneered by The Inga Foundation and the Cambridge University Alley Cropping Project, represent one of the greatest examples of agricultural appropriate technology in the world today .
What is Inga Alley Cropping?
According to Mike Hands, “The only truly sustainable system to emerge from our years of scientific research into slash and burn is alley cropping using nitrogen-fixing tree species from the genus Inga. In essence this system has the ability to recreate a version of the conditions found on the rainforest floor, or, in other words, the conditions supporting plant growth in one of the world’s most productive natural systems. In this system, the trees are planted as seedlings in a series of hedgerows forming alleys which run along the contours of the terrain. The Inga leaves quickly create a thick layer of tough mulch on the soil surface. Initially the Inga is allowed to completely dominate the site in order to recapture it by shading out the weeds and grasses – a process usually requiring 1½ to 2 years. Over this time the Inga also restores and rebuilds the soil, fixing nitrogen and recycling phosphorus.”
Once these alleyways of nitrogen fixing trees have had the opportunity to establish, they can be intensively pruned on a yearly basis. The trimmings and leaves are then used as mulch for the annual crops planted between the rows of Inga. Also during pruning, firewood can be obtained from the larger branches of the Inga trees. Families can obtain all the firewood they need from the Inga plots, possibly eliminating another cause of deforestation in these regions. Then, as the annual crop matures between the rows, the Inga itself is recovering from pruning, providing some shade to the cash crop as it grows in this region of intense sunlight. After harvest of the annual crop the Inga is left to grow until the next planting season arrives, by which time the trees have fully recovered and the whole cycle is ready to be repeated. This system allows for a consistent harvest from the same land year after year by recreating the conditions found on the floor of the rainforest. An additional benefit of mimicking the patterns of the rainforest is that the Inga helps to out-compete the quickly growing grasses that will establish in these regions in lieu of a mature forested system. This biological weed control is important because without it, as Mike stated, “Securing a harvest can require a huge amount of labor in terms of weeding per hectare per year. In fact, it is often the combination of this takeover by grasses, as well as the loss of fertility, that forces farmers to abandon their plots after a few years and clear new areas of forest.”
The Path Towards Something Great
Growing up in Gloucestershire, England, Mike Hands spent his childhood immersed in the beauty of the natural world – constantly playing in the woods and streams. The love Mike has for the outdoors is a part of him, and he attests that being brought up in this environment is what has driven his interests in ecology organic gardening. Always an adventurous spirit, he spent many years in Africa and Central America working as a cartographer and then later with various development projects in these regions. It was during his work and travels in the tropics that Mike was exposed first hand to slash and burn agriculture. “Particularly when I was in some parts of Africa, walking through miles and miles of burnt Guinea savannah forests, it was just devastating seeing the effects.” He would never forget the scale of deforestation that he’d witnessed, and it would later provide inspiration for a major change in his life.
It came to a time when Mike Hands began to feel a little restless. He refers to it as a mid-life crisis that he sensed before it hit him. “So, I went back to school, Cambridge, where I enrolled in a two year masters specifically to get my teeth into this.” Fully immersed in the science of slash and burn agriculture, he tried to read everything that had previously been published on the subject. What came of this was the discovery that the information available on the ecology of slash and burn was incomplete and sometimes contradictory. This is when he realized that he would have to do things differently than they’d been done before. “I began to focus on the availability of nutrients being the major factor in slash and burn. It’s the reason that the systems fail that was the real question to me.” It is when the land becomes unfertile that the farmers turn towards slashing and burning new land. Mike knew that if he was able to figure out how to keep the nutrients in the system he would be well on his way to creating a new technique that would provide an alternative to continuous slash and burn agriculture.
What is different about the Inga approach that sets it apart?
During years of dedicated research looking at soil samples, crop productivity, and overall system health, Mike and his colleagues came across many important findings that would lead to the development of the Inga Alley Cropping system. He makes clear that they initially started looking at alley cropping as a viable alternative to slash and burn because others were already making claims that alley cropping was the sustainable solution to the problem. “It was the reason these (agricultural) systems fail that was the real question to me,” said Mike. The original prevailing mentality in creating alley cropping systems was to use small leaved, perennial legumes to establish the alleys. The small leaves take little time to decompose allowing them to breakdown in time for the nutrients to become available to the food crops growing in the alleys. In theory this is sensible, but many factors are involved that precede, and go beyond nutrient availability, to promote a healthy and successful alley cropping system.
Mike’s team discovered, early on, that the species suggested for intercropping in these tropical regions – Gliricidia sepium and Erythrina fusca – weren’t providing adequate weed suppression, enough food for the soil food web, or enough cover on the soil to prevent evaporation. When setting up the field trials, there was an idea to try some varieties of Inga, a perennial legume tree species that grows in the tropics. Although it came against the advice of some regional advocates, Mike decided to include Inga along with the other trial species. Unlike the plots containing Gliricidia and Erythrina, the alley cropping experiments in involving Inga had some very impressive results. Inga was already being used as a shade tree on coffee plantations in the region, but it’s effectiveness in annual cropping systems was initially surprising. In addition to finding a suitable perennial plant species for use in the alleyways, one other aspect of the experiment proved to be the link to understanding why the Inga was so much more effective than its counterparts in experimentation. Different nutrients were the other variable (beyond different legume species) that was experimented with in these trials. The second discovery about growing crops on this land, that had just been slashed and burnt, came in the crop’s overwhelming positive response to phosphorus compared to other nutrients. While speaking with Mike it was clear that one element was key to establishing and maintaining the productivity of these agricultural systems – phosphorus.
The approach developed at this point was based on years of soil tests combined with physical successes witnessed in the years of field trials. All of the initial soil testing revealed a massive deficit and loss of phosphorus over time in these soils following the initial slashing and burning. It is often assumed that the soils supporting a rainforest are the most productive in the world. This is true to a certain extent, but only when the forest is a fully operating ecosystem. When the vegetation is removed and the ground exposed to the vast amounts of rain and sun that occur in the tropics, the area is quickly reduced to an acidified, lifeless parent material. All that once supported an incredible biodiversity is soon gone, including the massive amount of nutrients that were packed into the vegetative material that was recently incinerated. As Mike mentioned, figuring out why the systems fail was of most interest, and this is because it’s allowed him to critique the positive results in a way that has led to the establishment of his valuable technique – Inga Alley Cropping. The Inga has leaves that are a lot more substantial than those of the Gliricidia or Erythrina. They can take a several months as opposed to weeks to decompose, but at the same time it is a very vigorously growing plant that can handle the heavy yearly pruning, thus adding more organic material to the forest floor. This large quantity of leaves and small branches are the fuel that feeds the vast colonies of microbes that live just below the soil surface. As was previously mentioned, this thick mulch controls difficult weeds and protects the soil from heavy evaporation, but the most important factor is the increase in soil microbial activity.
The hypothesis behind establishing Inga Alley Cropping is that the phosphorus in this system, required for long term crop productivity, is maintained by the healthy, thriving diversity in the soil microbial population. The soils themselves won’t readily hold phosphorus in a manner that is available to crops. In turn, the soil microbes have adapted to become the primary vehicles for phosphorus cycling in these tropical ecosystems. It is important to note that Inga may not be a prevalent species in all tropical regions, but the tenants of establishing alley cropping using a hardy perennial legume (with similar growth characteristics to Inga) to recreate the conditions of the rainforest floor remain the same throughout congruent regions in the rest of the world. Without the soil microbes, which require rainforest floor-like conditions to thrive, the self-reinforcing cycle of slash and burn annual agriculture will continue unbroken.
The Inga Foundation has been able to set up pilot projects and Inga nurseries in a few of the countries where slash and burn is most prevalent, and adaptation of these techniques is slowly coming. While it is understandably difficult to convince rural people, often in subsistence farming situations, to adopt a new experimental approach as their food production system, with time the value and application of Inga Alley Cropping will potentially be realized by thousands, if not millions of farmers worldwide. Envisioning the vast impact that this technique could have on our planet, both socially and environmentally, is staggering yet empowering to consider .
Check out the Inga Foundation website – ingafoundation.org
Also, click here to read our full conversation with Mike Hands.
Hands, M. R. 1998. Invited chapter: The uses of Inga in the acid soils of the Rainforest zone: Alley-cropping Sustainability and Soil-regeneration. In: Pennington, T.D. and Fernandes, E.C.M. (eds.) The Genus Inga: Utilization. The Royal Botanic Gardens, Kew. England.
Hands, M. R., Harrison, A.F. and Bayliss-Smith, T. P. 1995. Invited chapter: Phosphorus Dynamics in Slash-and-Burn and Alley-cropping Systems of the Humid Tropics. In: Tiessen, H. (ed) Phosphorus in the Global Environment. SCOPE; UNEP sp. Publication. John Wiley.
Skole, D. L., W. A. Salas, and C. Silapathong. 1998. Interannual variation in the terrestrial carbon cycle: significance of Asian tropical forest conversion to imbalances in the global carbon budget. Pp. 162-186 in J. N. Galloway and J. M. Melillo (Eds) Asian Change in the Context of Global Change. Cambridge: Cambridge University Press
Steif, Colin. “Slash and Burn Agriculture.” About.com – Geography. About.com, 2013. Web. 29 May 2013.
Weisman, Alan. Gaviotas: A Village to Reinvent the World. White River Junction, VT: Chelsea Green, 1998. Print. “Deforestation of Tropical Rain Forests.” The Rain Forest Report Card. Tropical Rain Forest Information Center, 19 Nov. 1998. Web. 29 May 2013.
“The History of Agriculture.” Wikipedia. Wikipedia Foundation, 22 May 2013. Web. 29 May 2013.
The Inga Foundation. The Innocent Foundation, 2010. Web. 29 May 2013.
U.S. And World Population Clock. United States Census Bureau, 29 May 2013. Web. 29 May 2013.
What do you think? Leave a comment below.
Sign up for regular Resilience bulletins direct to your email.
This is a community site and the discussion is moderated. The rules in brief: no personal abuse and no climate denial. Complete Guidelines.