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 worlds 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.
A year in 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 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.
To learn just how much difference these changes make, check out our blog, visit our Pinterest page, or read our Inga in Action page to hear the stories of some local families who have taken up Inga alley cropping.