Inga FAQ

Our current answers to the most common Inga alley cropping questions.

This FAQ is the public version of what we tell implementing farmers on our sites.

It's based on the best practice guidelines we have been able to aquire from grassroots practitioners, published literature, and personal communications among experts. We do not claim to be the definitive sources and instead refer to references section, Hands, et. al. 2021, and practical training schools.

In a hedgerow of Inga edulis, what is the planting distance between trees?

50 cm. This produces more leaf litter on the soil and suppresses weed growth.

How many meters wide should the alley be?

4 m. This is the spacing between hedgerows, allowing enough light for crops while maintaining permanent mulch cover from the Inga canopy.

How many seeds or seedlings fit in a one-hectare plot?

5,000 Inga edulis seeds or seedlings per hectare. Note: Savimbo caps per hectare payments at $250 trees. (See Dimensions section, under Density)

What plants can be sown alongside Inga edulis?

Both short-cycle crops (maize, beans, vegetables) and long-cycle crops (fruit trees, pepper grown on Gliricidia sepium living stakes, turmeric, tropical hardwoods) can be planted with Inga edulis but configurations differ (alleys vs . (See Dimensions section)

When should Inga edulis be pruned?

The first pruning is done when the tree has reached approximately one year of age. If the tree is growing very rapidly, it can be pruned earlier. The stake is cut at approximately waist height of the person pruning (meaning ~1.5m). (See Pruning section)

During the growth of Inga edulis, should site visits be conducted, and how often?

Yes. Savimbo conducts 5 site visits during the growth period although only two are required for payments (6- and 12-month visits. (See Validation section)

• First visit: 6 weeks after planting
• Second visit: 3 months after planting
• Third visit: 6 months after planting (independent validation for payments)
• Fourth visit: 9 months after planting
• Fifth visit: 12 months after planting (independent validation for payments)

How should weed control be carried out on the Inga edulis plot?

From the time the Inga edulis seedlings are planted, weeding is done manually, using tools such as a machete or araña (hand-rake), without the use of chemicals. But weeding is only needed during the first ~2 years, establishment phase. Once the Inga canopy closes and the recalcitrant mulch is in place, weed growth drops to near zero. (See Weeding section)

When Inga edulis is pruned, what is done with the leaf litter and the wood?

The leaf litter is spread directly onto the soil of the plot, where it serves as an excellent organic fertilizer (providing nitrogen, and more importantly, phosphorus). On our sites, wood is used to make biochar (charcoal) which is not the recommended use on the Inga Foundation sites who prefer it for firewood or cookfires. (See Pruning section)

When Inga edulis is planted on a plot, should fertilizers be used?

We're in agreement with the Inga Foundation that chemical fertilizers (synthetic ammonium nitrate, urea, or triple superphosphate) are not used, and not necessary, since Inga edulis itself serves as the organic fertilizer the soil requires. However Hands is adamant that mineral supplements are essential in degraded tropical soils at planting to prevent failure, preferring rock phosphate (slow-release, sorbed onto the mulch layer) and dolomite/K-Mag as mineral amendments. (See Fertilizer section)

How should Inga edulis be sown — by direct seeding or not?

We've tried both; there are pros and cons to each. Previously, planting was done as follows: first, seeds were collected, then germinated, then bagged in a nursery, and finally transplanted to the field. Recently, we conducted a direct seeding experiment — that is, the seed is sown directly into the ground at the planting site. It was easier, but we'll see if it turns out as high of quality. (See Seeding section)