On this page we share answers to your questions and practical lessons we have learned. These lessons are relevant to all aspects of Inga alley cropping, it’s implementation and how best to promote the Inga system to farmers.
Do Inga Trees grow at different rates in different countries?
The Inga trees seem to grow faster in Cameroon and Ecuador than in Honduras. This is our impression rather than accurate measurement. This could be due to Cameroon and Ecuador being closer to the equator.
What do I do if the Inga grows too fast?
Fast growth can cause the Inga to overgrow a crop which is still growing. This may lead to a reduced (or even no) harvest. The remedy is to prune the Inga again while the crop is growing.
If the trees are growing fast then you may want to consider leaving a shorter internal of 4 weeks between pruning and sowing instead of the usual 6 weeks. Do not do this for the very first set of crops on a new Inga plot as it might not allow enough time for the first mulch to be formed on the ground.
We recommend making sure new farmers are aware of the potential for overgrowth as it does happen particularly at times of year that are optimal for the Inga.
The Inga have grown too fast and are badly shading the struggling maize.
What crops can I plant?
We have had success with many different crops, including: maize, cassava, pineapples, cocoyams, beans, peppers, ground nuts, and many more.
Can I plant crops while the Inga are still very young?
We have seen some farmers have a tendency to plant maize in the alleys while the Inga is still young and has not yet been pruned. This does not work well. At a minimum you must avoid planting a tall crop that will shade the Inga.
Should we plant the seeds in bags or directly into the ground?
Normal practice is to plant the trees in poly bags.
These are filled with forest soil that also contain the necessary microorganisms (nitrogen fixing bacteria and mycorrhizal fungi that take up the phosphorus). For more details on ensuring these microorganisms are present see Seed Collection and Planting out on this page.
Bags containing seedlings should be kept moist prior to planting and be planted out within a few days. Seedlings are generally more robust than planting out seeds, though both can be used.
The disadvantage is that the bags cost money and create waste. For that reason we have been experimenting with planting directly into the ground.
Planting directly in the ground (bareroot method) has been found to be successful in some of the planting done in our Ecuador project, and the local project manager claims that these trees grew better than those first grown in bags and then planted out.
We have done some experimentation with planting bareroot in a nursery but do not at present have results to report.
Inga has also been successfully propagated by cuttings. This has the disadvantage that there will then be no genetic variability.
Comments from one of our Cameroon partners, Atanga Wilson:
You have now planted Inga seeds in three ways: polybags, bareroot and direct into the ground. Which method do you think is the best?
Polybags or bareroots.
The choice depends on how far the nursery is to the farm where the Inga is to be planted. It also depends on the regularity of rain fall. But Inga seedlings raised with biodegradable poly bags are usually the best option.
You say some of the bareroot seedlings died after they were transplanted. Why do you think they died?
This happened when they were transported by walking long distances on foot from the nursery to the farm in the hot sun in the middle of the day.
How did the compare with the ones you first grew and planted in poly bags?
The poly bag ones do better if they are planted and there is no rainfall for 3 days after transplanting. But there is no difference from those with the poly bags planted in the morning and evening in the hours when the rain falls.
How does planting the seeds directly into the ground compare with these other methods?
Seeds planted directly grow very slowly because they don’t get the same care on the farm as they would have in the nursery. They face more of a shock when there is a dry spell or absence of rain for a week or two.
In summary, I recommend biodegradable poly bags for Inga nurseries. If no biodegradable poly bags are available then go for bareroots Inga nurseries and trek for very short distances to plant the bareroot seedlings.
How high up the mountain can we do Inga alley cropping?
We have Inga plots at 800m altitude on the edge of La Bonita forest in Ecuador that have grown well. We also planted Inga higher at 1800m and demonstrated conclusively that it will not grow at that height – the seeds germinated but hardly grew. 1600m is probably the maximum altitude.
These results are from Ecuador. Ecuador is right on the equator, so it is likely that for countries further away the Inga would not thrive as high as it would in Ecuador.
Do we need to add rock phosphate?
Rock phosphate is recommended by the original researcher for the Inga alley method. However we have had good results in both Cameroon and Ecuador without using it. We therefore do not recommend it, at least to begin with. It might potentially be necessary in some very poor soils.
What is the maximum width for the alleys?
We normally plant alleys with a width of 4m. However if growing conditions are good it may be possible to plant 5m or even 6m wide alleys.
Can you use Inga outside the alley system?
We have seen what when farmers put their Inga into cocoa farms rather than for alley cropping, this can boost their cocoa production significantly. It also provides a good source of Inga seeds, which could be used later to create an alley structure.
Are there any times of year to avoid planting Inga?
The Inga mulch is good at maintaining moisture so that crops can thrive even in some drought. But crops should nonetheless be sown when there is some rain. We have had crops fail because they were planted too late in the planting season. The Inga mulch cannot hold moisture when there is none to begin with.
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