What is Slash and Burn?
Slash and burn is a subsistence farming method used by millions of families in the tropics in which families cut down and burn an patch of forest in order to create an area of fertile soil on which they can grow their food. However, and here’s the catch, the soil fertility doesn’t last. Once cleared of trees and exposed to the strong tropical climate, the bare soil is rapidly stripped of nutrients. The first year lash and burn generally gives a good crop, the next year less good and, by the 3rd year, crops often fail completely. This forces families who depend on slash and burn to keep clearing new, fresh areas of rainforest every few years, just to survive.
Inga Alley Cropping: What is it and how does it work?
Inga alley cropping is the revolutionary alternative to slash and burn invented by Inga Foundation Director, Mike Hands, based on the insights gained through over a decade of research into slash and burn in partnership with Cambridge University. Of the different potential alternatives investigated by Mike Hands, the only truly sustainable system to emerge from years of scientific research was alley cropping using nitrogen-fixing tree species from the genus Inga. Inga alley cropping is capable of maintaining soil fertility and good harvests year after year, thereby breaking the cycle of slash and burn and allowing families to gain long term food security on one piece of land.
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, Inga 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.
A year in Inga alley cropping:
Once the Inga alleys have developed, the Inga trees are pruned. The prunings are used as mulch, thus protecting the soil and preventing further weed growth. Larger branches are used as firewood, allowing families to obtain all the wood they need for cooking from the Inga plots and thereby tackling another important cause of deforestation. The crop is then planted through the mulch within the pruned alleys. As it grows the Inga also recovers and regrows, providing the crop with some shade and protection from the sun. Once fully matured the crop is harvested. The Inga is then left to grow until the next planting season arrives, by which time they have fully recovered and the whole cycle is ready to be repeated, starting with pruning the Inga alleys once more.
This system delivers huge benefits through ensuring a reliable harvest year after year from the same plot of land with minimal labour required. By recreating the conditions naturally found on the forest floor, Inga out competes the aggressive invasive grasses which normally dominate the farmers’ plots. This biological weed control is hugely important as without it securing a harvest can require a huge amount of labour in terms of weeding per ha per year. In fact, it is often the combination of this takeover by weeds, as well as the loss of fertility, that forces farmers to abandon their plots and clear new areas of forest.
To learn just how much difference these changes make, check out our blog or newsfeed. Or alternatively, watch the 5 short films that chart the invention of Inga alley cropping and document the benefits it is now bringing to subsistence farming families.