The Practical Application of Inga Alley Cropping
Where is it Appropriate to use this Farming Method?
Inga alley cropping was developed as an effective, sustainable alternative to slash and burn agriculture in the rainforests and former rainforest lands. Here the soils are frequently degraded and acidic and Inga has good tolerance for such soils. Not all the Inga species are suitable. Caution needs to be exercised in parts of the world where the Inga tree is not native, but it has now been used widely in many countries without serious problems.
A Mega-cassava from an Inga alley! Photo by José, Ecuador
It typically takes between 8 months and two years to get Inga alleys established. The exact length of time will depend on how much sun and rainfall there is, the soil, and the care the farmer takes of the young trees. However, the yields are good. Compared to reusing previously cultivated plots, harvests can be as much as 15 times higher with Inga than without it. Costs are minimal. And of course the same plot can be used over and over. We know of plots that are now over a decade old and still providing yields as high or higher than at the start, as mulch builds up. Some farmers have noted that the harvest is better than even the first year they get on a fresh plot after burning primary rainforest. (We are in the process of gathering more quantitative data on this.)
How Well has it been Tried and Tested?
There have been over two decades of meticulous research followed by field trials1,2. The farmers who have taken it up have been able to stay on the same plot for many years and are very happy with it. At the end of the first field trials the plots had lasted six years with just one initial application of rock phosphate. They have continued since. The Inga recycles what the crops do not use. It also has mycorrhizae (fungi) in its roots which supply phosphorus. Even if, as the original researcher thought, some further rock phosphate would eventually be needed, it is expected that this would ensure a long fertile period and be very affordable for the farmers.
Since then however we have had many successful plots, particularly in Ecuador and Cameroon, some of which are over 10 years old, with no rock phosphate needed in either country. We therefore recommend that the system be tried without any such addition, and the rock phosphate be used only when if becomes apparent that it is really necessary.
Do the Farmers like it?
Yes, very much. The strongest proof of that is that after trying it on a small scale they typically want to expand their Inga plantings.
What is harder is to convince farmers to start it for the first time. They usually need to see it in operation in a demonstration plot. However, after a field worker from Guatemala had visited the Inga demo facility at CURLA and described and illustrated his visit with photographs of the Inga alleys, he reported that over 5,000 families in the Maya heartland wished to try it. Nonetheless we have seen the most success by showing farmers demo farms.
Victor Coronado, one of the first Honduran farmers to try Inga alley cropping, Now demonstrating it to other farmers. Photo by Antony Melville 2007
Moreover Inga is not a quick fix. It typically takes between 8 months and two years, from sowing the Inga seed to pruning and sowing the first crop. If the conditions are very poor, for example if the soil is particularly poor or initial weeding isn’t done, it can even take three years. During that time the farmers need support. This includes reassurance that it will work, technical advice, and financial help such as some form of micro credit until they get the benefits of the first crop. They also need seed and bags to grow the seed in, and may need fencing to protect the field. Sometimes the seeds have been planted successfully in the ground straight away, or nurseries using a bare root method have been used. These two methods save on costs. While the Inga is small low crops can be grown in the alley, but it is necessary to avoid crops that would shade the young trees and slow their growth.
The system has appealed particularly to farmers who have had to farm in the most difficult conditions, like on acid soil or on steep slopes. Inga alley cropping has been effective in preventing or reducing soil erosion on hillsides, even in very adverse weather conditions. This is clearly of great benefit to such marginalised farmers. It has also been very useful in reclaiming previously degraded barren land.
What does it cost the farmer in both time and money?
They need seed and bags to grow the seed in, fencing to protect the field, rock phosphate to start off the system and tools for planting and pruning. The research suggested some rock phosphate to start the system, however we are not using rock phosphate in Ecuador or Cameroon, and seeds sown directly into the ground have also grown well.
One challenge with adopting this system is the time it takes before the Inga plot becomes fully productive – anywhere between 8 months and 2 years. It may be possible to some carefully selected crops earlier, e.g. beans if the soil and climate are favourable. Valuable firewood is also typically obtained long before the first proper harvest.
Initially getting the system under way takes hard work, but once the Inga is well established the farmer saves time and energy. In the first year, to establish the system, the farmer has to pre-slash the site to keep down the weeds, then plant the Inga, and then slash the weeds again round the young trees till they are fully established. There needs to be a clear area of about a metre round the base of each tree. This might come to over 100 man-days effort per hectare. However many farmers want to start much smaller than that, for example with a tenth of a hectare, and this makes the initial work more manageable. More land can be put under Inga alley cropping in subsequent years.
From the second year on the alley cropping system requires very much less work than slash and burn (about half the man hours), as there is very little weeding to be done. Moreover for slash and burn additional time is often used to walk to the most recently cleared plot. This can be as much as 2 or 3 hours per day – a very long commute. The alleys can be permanently sited next the farmer’s home and do not move, thus saving this time.
Inga alleys right next the farmer’s house. Cameroon
The trees are pruned before they flower. If there is a need to harvest seed to expand the Inga to a new area, a tree needs to be left unpruned. This can be done at the end of one row. Funders might stipulate that in return for seed, the next farmer grows one such tree to supply their neighbours with seeds later (when they have seen how well the system works).
Sone with the other great product from his Inga alley: firewood. Photo by Atanga Wilson, Cameroon.
Is Inga alley cropping worth it? Just look at this Mega-cassava. Photo by José, Ecuador.
- Hands, M.R. 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. The Genus Inga: Utilization The Royal Botanic Gardens, Kew 1998
- Final Report to COMMISSION OF THE EUROPEAN COMMUNITIES DIRECTORATE GENERAL Project HND / B7-6201 / IB / 97 / 0533 (0 June 2002