Inga Edulis

Inga edulis and Its Relationship with Soil and the Environment: Experience from Sierra Leone.

Posted on the 12th of January 2026

Introduction:

Inga edulis, commonly known as Ice-cream bean, is a fast-growing, nitrogen-fixing leguminous tree native to Central and South America. It is widely recognized for its role in sustainable agriculture, soil restoration, agroforestry systems, and climate resilience.

In November 2018, Inga edulis was introduced to Sierra Leone through a partnership between Rory’s Well Charity (United Kingdom) and People’s Agenda for Development Sierra Leone (PAD-SL). This introduction was made possible through the technical and logistical support of Antony D. Evans and Gaston Bitto from Cameroon. Since its arrival, PAD-SL and partners have conducted practical field experiments to evaluate the performance of various food and cash crops under Inga edulis alley-cropping systems.

 Botanical and Ecological Characteristics of Inga edulis

Inga edulis belongs to the Fabaceae (legume) family, which gives it a unique ecological advantage:

•   Rapid growth with a dense canopy

•   Deep root system that stabilizes soil

•   Ability to fix atmospheric nitrogen through root nodules

•   Production of large quantities of organic biomass (leaves and pruning)

These characteristics make Inga edulis highly suitable for tropical environments, including the forest–savanna transition zones of Sierra Leone.

 Relationship between Inga edulis and Soil

Nitrogen Fixation and Soil Fertility

As a leguminous tree, Inga edulis forms a symbiotic relationship with nitrogen-fixing bacteria (Rhizobium). This process converts atmospheric nitrogen into forms usable by plants, resulting in:

•   Improved soil nitrogen content

•   Reduced need for chemical fertilizers

•   Enhanced crop productivity over time

This is particularly important in Sierra Leone, where many agricultural soils are nutrient depleted due to shifting cultivation and continuous cropping.

Organic Matter and Soil Structure

The regular pruning of Inga edulis produces large amounts of green mulch, which:

•   Increases soil organic matter

•   Improves soil structure and aeration

•   Enhances microbial activity

•   Improves water infiltration and retention

As the mulch decomposes, it releases nutrients gradually, supporting sustained crop growth.

Soil Conservation and Erosion Control

The tree’s root system binds soil particles together, while its canopy reduces the direct impact of rainfall. This leads to:

•   Reduced soil erosion

•   Protection of topsoil

•   Stabilization of sloping farmlands

These benefits are critical in areas prone to heavy rainfall and land degradation.

 Relationship Between Inga edulis and the Environment

Climate Regulation and Carbon Sequestration

Inga edulis contributes to climate change mitigation by:

•   Absorbing and storing atmospheric carbon

•   Reducing surface soil temperatures

•   Creating a favorable microclimate for understory crops

Its dense canopy helps reduce heat stress on crops and soil organisms.

Biodiversity Enhancement

The tree provides:

•   Habitat for beneficial insects and birds

•   Shade that supports diverse plant species

•   Improved ecological balance within farming systems

This aligns well with environmentally sustainable and conservation-based agriculture.

4.3 Reduced Dependence on Slash-and-Burn

One of the most important environmental benefits of Inga edulis is its role as an alternative to slash-and-burn agriculture. By restoring soil fertility naturally, farmers can reuse the same land continuously without destroying forests.

 Experimental Trials with Food and Cash Crops in Sierra Leone

Since its introduction in 2019, PAD-SL and partners have carried out field experiments to assess the performance of various crops under Inga edulis alley systems.

Crops Tested

The following crops have been tested:

1.  Maize

2.  Rice

3.  Groundnut

4.  Cassava (still under trial)

5.  Cocoa (still under trial)

Observed Results

•   Maize has shown excellent performance, growing vigorously within Inga edulis alleys due to improved soil fertility, moisture retention, and reduced weed pressure.

•   Rice, especially upland or “Wise Rice”, has also performed well under the alley-cropping system, benefiting from mulch cover and nutrient availability.

•   Groundnut has shown promising early results, particularly in improved soil conditions.

•   Cassava and Cocoa are still under long-term observation, as they require more time to assess yield response, shade tolerance, and root interactions.

These trials demonstrate that Inga edulis is highly compatible with mixed cropping and agroforestry systems in Sierra Leone.

 Significance for Sustainable Agriculture in Sierra Leone

The successful establishment of Inga edulis represents a major opportunity for:

•   Sustainable food production

•   Soil restoration and conservation

•   Climate-smart agriculture

•   Reduced farmer input costs

•   Improved rural livelihoods

The collaboration between Rory’s Well Charity (UK) and PAD-SL stands as a strong example of how international partnerships and local innovation can promote environmentally sound agricultural solutions.

Conclusion

Inga edulis has proven to be more than just a tree; it is a soil healing, climate friendly, and farmer supporting species. Since its introduction to Sierra Leone in November 2018 through Rory’s Well Charity and PAD-SL, and with the contributions of Antony D. Evans and Gaston Bitto, the tree has demonstrated strong potential to transform degraded farmland into productive agricultural systems.

The ongoing crop trials, especially with maize and rice, confirm that Inga edulis alley-cropping can play a critical role in sustainable agriculture, food security, and environmental conservation in Sierra Leone.