Using a sustainable alley-cropping agroforestry solution for local needs in the Amazon
We recently took ownership of a large piece of land (approx. 1 hectare) that 6 months earlier had been cleared of all its forest vegetation leaving a short piece of re-growth that was mainly sandy sub-soil which had been washed out of its topsoil. We decided this would be an ideal site to put into practice our knowledge of land regeneration on a grand scale, demonstrating how to get many of our food needs met whilst improving soils and yields over the years. Eventually to use this piece of land as a training site to show how anyone can replicate this model of regenerating the rainforest and to meet their needs for food, fuel, and fibre.
Typically in this region, people clear large tracts of rainforest like this to produce 1 or 2 rotations of annual crops until all the soil is washed out, they then move onto another piece to do the same. With the increase in population in this area there is no longer enough land for everyone to do this, this is one reason why 9 million hectares of rainforest have lost there original tree cover in Peru, of which 5.5 million is considered degraded/abandoned and 261000 more hectares gets added every year (See page 21 of Rehabilitación de áreas degradadas en la Amazonia peruana). By sharing the agroforestry techniques discussed here that allow the same piece of land to be sustainably harvested from continuously, we can help alleviate pressures on the rainforest.
First we analysed the situation; observing and interacting so that we could fully appreciate all the energy coming in and out of the land. This land had been cleared just prior to the dry season (June-September) and so we quickly decided to plant a recovery crop to protect and build soils. Resilient beans, yucca and corn were chosen and quickly planted. Luckily, in the forest above we found two springs that continued to give water throughout the dry weather and so we used these to water the recovery crop when needed.
For the rest of the year in our location, situated within the humid tropics of the Amazon rainforest basin, we frequently receive very heavy downpours of rain and so we needed any system designed to manage this heavy flow of water. As you can see from this picture, the landscape is relatively sloped surrounded by 10-15 year re-growth forest, containing two small valleys that form into one towards the bottom of the clearing. This gave us opportunities to redirect and spread this water flow throughout the landscape.
We did this by placing 6 dams in suitable places and then connecting these with swale systems. To make these swales, which are dug ditches and mounds on contour, we used the excess woody material from the cleared forest to give them a base structure and then layered soil and organic matter to build a healthy bed. We then planted these beds with more beans to protect and build the soil. In this system the ditch will be used as the main access pathway to the land.
On the downslope of the swales we planted a mix of nitrogen fixing trees, such as ice cream bean, leucaena and sesbania, to be used in an alley cropping format by being continuously chopped and dropped back to mulch the soils, eventually breaking down into healthy soil. On the upslope of the swales we planted vetiver, this bushy clump grass with its deep roots will heed erosion whilst accessing nutrients locked deep in the sub-soils, which can then be added to the top soil by chopping and mulching its grass stems.
The beauty of this system is that it will moderate the flow of water in the landscape just like the forest would; in a heavy downpour it slows and spreads the flow across the contour of the swale allowing it to percolate deeply into the soil causing little to no erosion. In a dry period the flow of water will continue within the soils so that the vegetation can always access water until the next rain comes to fill up the water stored in the soil. This animated video gives you a good idea of this process and the function of a swale in the landscape. Therefore, it will soon grow into the poly-culture system designed with many layers of vegetation all interacting to benefit each other and so produce a huge amount of diverse yield whilst building soil.
With the designed landscape now moderating the water flow we could now think about how to best plant the site. The upper most part of this land is heavily sloped and so we decided to plant a mix of cacao, macambo and ice cream bean trees so that we could get nutritious food without disturbing the soils here, this would also drop down nutrients into our more intensive systems below. In the rest of the land once the rotation of our cover crop is over and the rains return we will plant a highly diverse mix of mainly perennial crops with some annuals rotating with the wet and dry seasons. The main goal being to always produce healthy soil, as well fresh nutritious food.
In the dam systems we also saw opportunities to add aquatic plants for food and green mulches for the land. We are experimenting with 5 local varieties of rice in these areas and will soon see how they can be fully incorporated in the system, but more on that and the next rotation of crops in the next blog on this land.
Here’s some more before (27/07/2013) and after (20/09/2013) shots of the landscape showing how you can turn a degrading landscape into a productive one in under two months by replicating nature.
By Nick Boyce