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Volume 14, Issue 1, January - March 2025
CONTENT
Chair's Foreword
Indigenous Soil Management Practices
Earth Science Events
References and selected reading
Chair's Foreword*
In the current issue we revisit the topic of indigenous soil management practices.
Africans have been managing and conserving their soil and water and soil fertility for millenia. However, the recent history of the continent including its colonisation and neo-colonialism, has seen an adverse effect on African soil and soil fertility. Consequently, much of Africa’s landmass has suffered long term depletion of nutrients, moisture and soil material.
Western modes of agricultural land use in Africa such as intensive monocrop production repeatedly employed on the same land without fallow periods (as indigenous modes of agriculture employ[1] ) has mainly contributed to this degeneration of soils along with the environmental irresponsibility of some extractive industries that actually pollute the land - which is another matter. The degradation of the land we concern ourselves with here takes the form of the loss of soil due to erosion, loss of vegetation as well as soil nutrients leached out by rainfall and carried away by overland flow.
In the current day we know that a key solution to fixing our degraded lands lies in employing African indigenous technology.
This has been well established in the three decades since the output of the valuable 1992 report by the International Fund for Agricultural Development (IFAD) [2] by ongoing follow up work in the Sahel countries [3] where large areas of land were rehabilitated and hundred of thousands of tons of additional amounts of food were produced as a result of applying these simply enhanced indigenous techniques.
Indigenous Soil Management Practices in Africa
The purpose of this newsletter's focus on indigenous soil management practices is for the Society to
a) Encourage African use of indigenous technology, enhanced and improved as needed
b) Disseminate the Knowledge of indigenous technology and its applications within Africa and the African Diaspora.
We focus on the most well known and documented practices, still being employed on the continent today.
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| Acacia albida tree |
1) Planting Acacia trees
Planting the acacia albida tree fixes nitrogen in the soil via symbiotic bacteria. The tree sheds leaves during the rainy season which lead to more organic matter in the soil. This is known to improve soil moisture retention.
The trees also reduce wind erosion due to the resistance provided by their canopies. These canopies also provide a cover to prevent soil loss by direct rainfall.
The picture also shows a termite mound, which we recall from last newsletter, is also incorporated as part of a system of indigenous soil management practices[2a].
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| Applying mulch |
2) Mulching
This is the traditional technique of protecting the soil through covering it with organic material to protect it from direct rainfall and sunshine. It is effective in combating weeds. It is widely known to improve crop resilience in West Africa [4].
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| Stone Bunds |
3) Stone Bunds
Stone bunds are a line of stones arranged along the contours of the land in order to slow the flow of the water and trap sediment and organic material. In the long term, this enriches the soil. The bunds have the effect of reducing the amount of runoff and mitigating against the nutrient-rich top soil loss. The increased infiltration brought about will lead to more rapid groundwater recharge.
In the northern Ethiopian highlands large scale stone bunds building programmes were implemented to curb soil erosion. The study of the programmes concluded that crop yields increased by 7% compared to yields when there were no stone bunds[5].
4) Trash Lines
These are obstructions/barriers arranged to slow down overland flow or runoff draining from the catchment and hence reduce erosion. They consist of crop and plant residues and debris. They serve to eventually increase infiltration of water and hence assist in the groundwater recharge. They accumulate organic matter.
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| Terracing - Rwanda |
5) Terracing
This practice refers to the stepped platforms on slopes constructed across terrain in order to manage erosion and facilitate farming on steep slopes. The stepped constructions serve to greatly reduce the energy of the runoff and slow its velocity. The flattened terrain allows for greater water infiltration and hence more water retention and speedier recharge of groundwater. It also assists in retaining soil nutrients that would have been washed away without stepped slopes.
A study on the effect of terracing during the Ethiopian drought of 2015 provided evidence that terraces have potential to help farmers deal with current climate risks[6]. A meta analysis by Wei et al., 2016 [7] found that terracing was on average 11.5 times more efficient at controlling erosion than non- terraced plots.
By reducing plot steepness terraces affect soil composition, hydrology and hence plant growth. Since, as already mentioned, terraces improve groundwater recharge rates, as well as reducing runoff and enhancing the soil nutrients content.
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| Check dam - Ethiopia |
6) Check Dams
These are small barriers built across gullies (channels in the landscape created by erosive overland flow) using stones, logs, or earth to slow the flow of runoff. The dam serves to trap sediment and hence conserve soil as well as moisture. The effect is to recharge the groundwater and increase the level of the water table. The sediment also contains organic material which improves the organic material content of the soil, further improving its capacity to retain moisture.
Check dams are used all over the globe for control of torrential flows. Through experience and numerous case studies, people have realised their advantages in land development, environmental improvement, agricultural production, erosion gully stability and the mitigation of intensive flooding[8].
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| Zai planting pits |
7) Zai Planting Pits
In Burkina Faso, the traditional form of agricultural planting pit was enhanced. The Zai planting pits are larger. Zai planting pits are 30-40cm in diameter and 10-20 cm deep. The bottom of the planting pit is lined with manure, which retains moisture in the planting pit as well as providing fertiliser for the crops planted in the pit.
As emphasized by further studies in Nigeria [9], it is accepted that Zai along with other indigenous techniques are an effective way of improving degraded land and reducing vegetation loss and increasing bio-diversity. Progress was seen in Niger and Burkina Faso where people rehabilitated many hectares, and increased the food yield many fold. In the report by Reij et al [10] various methods applied in Burkina Faso including Zai rehabilitated 200,000 - 300,000 ha and resulted in additional yield of 80,000 tons of food. In Niger, an even greater land area was rehabilitated: 5 million ha and there was an additional yield of 500,000 tons of food.
Earth Science Events
20 May 2025
International Conference on Environmental and Life Sciences
VENUE: Kenema, Sierra Leone
21-22 May 2025
Environment Social and Governance (ESG) Climate Africa Summit
VENUE: Nairobi, Kenya
2 June 2025
International Conference on Environmental Science & Engineering
VENUE: Gulu, Uganda
18–21 August 2025
VISION: We are excited to announce the TC/ESG25 Conference, a collaboration between the Transformations Community, the Earth System Governance Project (ESG), and Wits University.
VENUE: Johann & Krugee National Park, South Africa
1 September 2025
International Conference on Environmental Science & Engineering
VENUE: Kisumu, Kenya
5 September 2025
International Conference on EEnvironmental Meteorology & Climatology
VENUE: Bamako, Mali
References
[1] Bado, V., Savadogo, P., et al., Technical Report. Restoration of Degraded Lands in West Africa Sahel: Review of Experiences in Burkina Faso and Niger, International Fund for Agricultural Development (IFAD).
[2] Soil and Water Conservation in Sub-saharan Africa, International Fund for Agricultural Development (IFAD), Rome 1992.
[2a] Newsletter #53 - Society of African Earth Scientists.
[3] Reij, C., Smale, M., and G. Gray, Re-Greening the Sahel: Farmer-led Innovation in Burkina Faso and Niger, in Miliions fed: Proven success in agricultural developments, International Food Policy Research Institute, Washington 2009, p.53-58.
[4] Lamers, J., Bruentrap, M., and Buerkert, A., The Profitability of Traditional and Innovative Mulching Techniques Using Millet Crop Residues in the West African Sahel, Agricultural Ecosystems and Environment, Vol. 67, Issue 1, January 1998, pages 23-35.
[5] Vancampout, K., Nyssen, J., Gebremichael, D., et al., Stone bunds for soil conservation in the northern Ethiopian highlands: Impacts on Soil Fertility and Crop Yield, Soil and Tillage Research, Vol. 90, Issues 1-2, November 2006, pages 1-15.
[6] Kosmowski, F., Soil Water Management Practices (terraces) helped to mitigate the 2015 drought in Ethiopia, Agricultural Water and Management, Vol. 204, 31 May 2018, pages 11-16. https://doi.org/1016/j.agwat.2018.02.25
[7] WeiWei et al., Global synthesis of the classifications, distributions, benefits and issues of terracing, Science Direct, Elsevier, 2016. https://www.sciencedirect.com/science/article/pii/S0012825216301313
[8] Abbasi, N.A., et al, The use of check dams in watershed management projects: Examples from around the world, Sci. Total Environ. 2019.
[9] Danjuma, M.N., and Mohammed, S., Zai Pits System: A Catalyst for Restoration in the Dry Lands, Journal of Agriculture & Veterinary Sci., Vol. 8, Issue 2, Ver. 1 (2015).
[10] Reij, C., Smale, M., et al. Ibid.
*Board of the Society of African Earth Scientists: Dr Enas Ahmed (Egypt), Osmin Callis (Secretary - Guyana/Nigeria), Mathada Humphrey (South Africa), Damola Nadi (Nigeria), Dr Chukwunyere Kamalu (Chair - Nigeria).
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