Cocoa farming is a vital source of income for millions of families in tropical regions like Cameroon, Ghana, and Côte d’Ivoire. However, soil degradation and climate change are threatening the future of this critical industry.
A 2025 study published in Environmental Challenges offers groundbreaking insights into how sustainable cocoa farming practices can combat these challenges.
By analyzing the interactions between cocoa farm age, slope gradient, and shade levels, researchers have uncovered strategies to improve soil fertility and ensure long-term productivity.
The Importance of Soil Health in Cocoa Farming
Cocoa farming contributes significantly to the economies of tropical nations. For example, it accounts for 3% of Cameroon’s GDP and 14% of Côte d’Ivoire’s GDP. However, decades of intensive farming have led to severe soil degradation.
In West Africa, aging cocoa farms have reported 30% yield losses due to nutrient depletion.
Traditional monoculture systems, where cocoa is grown without shade trees, worsen the problem by accelerating soil erosion and biodiversity loss.
In contrast, agroforestry systems—which integrate cocoa with shade trees like Gliricidia or Leucaena—offer a sustainable alternative. These systems improve soil health by recycling nutrients through fallen leaves, reducing erosion, and storing carbon.
Despite these benefits, many farmers lack clear guidelines on how to balance shade, slope, and farm age for optimal soil fertility. This study fills that gap, providing actionable insights for sustainable cocoa farming.
How the Study Was Conducted
The research focused on two distinct regions in Cameroon: Ntui, a forest-savanna transition zone with sandy soils, and Ebolowa, a tropical rainforest with clay-rich soils.
Over 108 farms were analyzed, with 54 plots in each region. Each plot measured 2,500 square meters, and soil samples were collected from a depth of 0–30 cm. Scientists evaluated three key factors:
- Shade Levels: Measured using the Gap Light Analysis Mobile App (GLAMA), which calculates canopy cover. Farms with over 60% shade were classified as high-shade, while those below 40% were low-shade.
- Slope Gradient: Categorized as gentle (0–5°), moderate (5–15°), or steep (>15°).
- Farm Age: Divided into young (0–10 years), mature (10–30 years), and old (>30 years).
Soil samples were tested for organic matter, nitrogen, phosphorus, and micronutrients like zinc and copper. The cation exchange capacity (CEC)—a measure of the soil’s ability to retain nutrients—was also analyzed.
Based on these parameters, soils were classified into four fertility levels: high, medium, low, and very low.
Key Findings on Shade, Slope, and Farm Age
1. The Role of Shade Trees in Boosting Soil Fertility: Shade trees emerged as a cornerstone of sustainable cocoa farming. Farms with high shade (>60% canopy cover) had 2.8% organic matter, compared to 1.9% in low-shade farms.
Organic matter improves soil structure, water retention, and microbial activity, creating a healthier environment for cocoa roots. Additionally, shaded soils retained 0.15% nitrogen, nearly double the amount found in unshaded plots.
Nitrogen is essential for leaf growth and chlorophyll production, directly impacting cocoa yields. Phosphorus levels also benefited from shade.
High-shade farms maintained 18–22 mg/kg of phosphorus, a nutrient critical for root development and energy storage. In contrast, low-shade farms saw phosphorus drop to 8–12 mg/kg due to erosion and nutrient leaching.
These results highlight the importance of shade trees in protecting soil health, especially on slopes prone to water runoff.
2. The Impact of Slope Steepness on Nutrient Loss: Slope gradient played a significant role in soil fertility.
Steep slopes (>15°) lost 30–40% of magnesium, a nutrient vital for photosynthesis, compared to gentle slopes. Magnesium deficiency can lead to yellowing leaves and reduced pod formation.
Furthermore, the cation exchange capacity (CEC)—a measure of the soil’s ability to hold nutrients—dropped from 12 cmol/kg on gentle slopes to 7 cmol/kg on steep slopes.
Erosion was a major issue on steep terrain. Rainwater washed away topsoil and nutrients, a process known as oblique drainage.
For example, phosphorus levels fell by 25% on slopes steeper than 15°, even in mature farms. To combat this, researchers recommend planting cover crops like Pueraria phaseoloides or building terraces to slow water flow and retain soil.
3. How Farm Age Influences Soil Health: Soil fertility followed a clear pattern based on farm age. Young farms (0–10 years) had low organic matter (1.5%) and phosphorus (6–8 mg/kg) due to recent deforestation and limited organic inputs.
As farms matured (10–30 years), fertility peaked, with organic matter reaching 3.2% and phosphorus rising to 15–18 mg/kg. This improvement was linked to the growth of shade trees and the accumulation of leaf litter.
However, old farms (>30 years) faced severe nutrient depletion. Phosphorus levels dropped to 4–6 mg/kg, and CEC declined by 35%, making it harder for the soil to retain nutrients.
These findings emphasize the need for targeted fertilization in older farms, particularly with magnesium and phosphorus supplements.
4. Regional Differences Between Ntui and Ebolowa: The study revealed stark contrasts between the two regions. In Ntui’s forest-savanna transition zone, 35% of soils were high fertility, primarily under mature cocoa farms with high shade.
However, 39% of soils were very low fertility, often linked to old farms on gentle slopes with inadequate shade. In Ebolowa’s tropical rainforest, the situation was more dire.
A staggering 87% of soils were classified as very low fertility, especially under old cocoa plantations on gentle or moderate slopes.
Only 9% of soils had medium fertility, found in young farms on steep slopes with high shade. These regional differences underscore the need for location-specific farming strategies.
Practical Strategies for Farmers and Policymakers
For Farmers: (Tailored Approaches Based on Farm Conditions) Young farms require organic mulches like cocoa husks or compost to kickstart soil fertility. Mature farms benefit from balanced NPK fertilizers to sustain nutrient levels, while old farms need targeted supplements to address deficiencies in magnesium and phosphorus.
On steep slopes, terracing or planting cover crops can reduce erosion. Maintaining 40–60% shade is ideal—enough to protect soil without blocking sunlight.
Farmers are encouraged to plant nitrogen-fixing trees like Gliricidia sepium, which enrich the soil naturally.
For Policymakers: (Supporting Sustainable Transitions) Governments can promote sustainable cocoa farming by subsidizing soil testing kits and agroforestry training programs. Certifications like Rainforest Alliance or Fairtrade should be incentivized to reward eco-friendly practices.
Additionally, land-use policies should restrict cocoa farming on steep slopes unless erosion control measures are in place.
For Chocolate Companies: (Investing in Sustainability) Chocolate companies play a crucial role by sourcing beans from farms that use shade trees and organic fertilizers. Initiatives like carbon credits for agroforestry systems can offset environmental costs while supporting farmers.
Challenges and Future Research
While this study provides valuable insights, its findings are specific to Cameroon. Replicating the research in other cocoa-growing regions like Ghana or Indonesia could reveal new patterns. Long-term monitoring over 50+ years is also needed to understand how climate change impacts soil health.
Smallholder farmers often lack resources to implement shade trees or soil tests. Addressing these socioeconomic barriers requires collaboration between governments, NGOs, and the private sector.
Conclusion: Building a Sustainable Future for Cocoa
This study highlights that sustainable cocoa farming requires tailored approaches based on farm age, slope, and shade. Mature farms on gentle slopes with high shade offer ideal conditions for sustainable yields.
However, urgent action is needed in areas like Ebolowa, where 87% of soils are degraded. By implementing agroforestry, precision fertilization, and policy support, we can protect livelihoods and ecosystems.
Choosing ethically sourced chocolate promotes the message that sustainability and productivity can coexist.
Power Terms
1. Agroforestry: A farming system where trees and crops (or livestock) are grown together on the same land. This helps improve soil fertility, biodiversity, and farmer income. For example, cocoa trees grown under shade trees like banana or timber species.
2. Soil Fertility: The ability of soil to provide essential nutrients to plants for growth. High fertility means the soil has enough nitrogen, phosphorus, and other nutrients. Poor fertility leads to low crop yields.
3. Shade Rate: The amount of sunlight blocked by trees in a cocoa farm. High shade (>60%) means more tree cover, which keeps soil moist and cool. Low shade (<40%) means more sunlight reaches cocoa plants, which can increase yields but harm soil over time.
4. Slope Gradient: How steep the land is. Measured in degrees, slopes affect water flow and soil erosion. Steep slopes (>15°) lose more soil nutrients due to rainwater washing them away.
5. Cation Exchange Capacity (CEC): A measure of how well soil can hold and supply nutrients like calcium and magnesium to plants. High CEC means fertile soil. Formula: Measured in cmol/kg (centimoles per kilogram of soil).
6. Organic Matter (OM): Decayed plant and animal material in soil. Improves water retention and nutrient supply. Example: Fallen leaves that decompose into humus.
7. pH: A scale (0-14) showing how acidic or alkaline soil is. Cocoa grows best in slightly acidic soil (pH 5.5–7). Too acidic or alkaline soils harm nutrient uptake.
8. Nutrient Depletion: When soil loses nutrients faster than they are replaced. Common in old cocoa farms where harvested beans remove nutrients without fertilizer use.
9. Carbon Sequestration: Storing carbon in soil or plants to reduce climate change. Shade trees in cocoa farms capture CO₂ from the air.
10. Litter Cycling: Fallen leaves and branches decomposing to recycle nutrients back into the soil. Important for maintaining fertility without chemical fertilizers.
11. Bulk Density: How compacted the soil is. High bulk density means poor root growth and water movement. Measured in grams per cubic centimeter (g/cm³).
12. Effective Cation Exchange Capacity (ECEC): Similar to CEC but adjusted for soil acidity. Shows how well acidic soils can still hold nutrients.
13. Nitrogen (N): A key nutrient for plant growth. Cocoa needs nitrogen for healthy leaves. Lack of nitrogen causes yellowing leaves.
14. Phosphorus (P): Vital for root and fruit development. Low phosphorus leads to small cocoa pods. Measured in mg/kg (milligrams per kilogram of soil).
15. Potassium (K): Helps cocoa plants resist diseases and drought. Found in banana peels, often used as natural fertilizer.
16. Mehlich III Solution: A chemical mix used to test soil for nutrients like phosphorus and potassium in labs.
17. Structural Stability Index (ISS): Measures how well soil resists erosion. Formula:
ISS=1.724×Organic Carbon(Silt+Clay)×100
Higher ISS means stronger soil.
18. Aluminium Toxicity (Kamprah Index, m): High aluminium in acidic soils harms roots. Formula:
m=Aluminium×100(Exchangeable Cations+Aluminium)
A value >60% is toxic.
19. Zero Deforestation: Policies to stop forest loss, like growing cocoa without cutting down trees. Important for climate and wildlife.
20. REDD+: A UN program paying countries to protect forests. Helps cocoa farmers adopt sustainable practices.
21. Monoculture: Farming only one crop (like cocoa without shade trees). Causes soil depletion and pest outbreaks.
22. Agroecosystem: A farming area including crops, soil, water, and climate. Cocoa agroecosystems need balanced shade and nutrients.
23. Precision Nutrient Management: Customizing fertilizer use based on soil tests. Better than one-size-fits-all approaches.
24. Humid Tropical Forest: A hot, rainy region with dense forests. Cocoa grows well here but soils lose fertility quickly if mismanaged.
25. Composite Soil Sample: Mixing multiple soil samples from one farm to get an average nutrient reading. Ensures accurate lab results.
Reference:
Biloa, J. B., Monique, A., Giveta, M. H., Fiaboe, K. K. M., Samuel, N. N., Mandah, P. V., Essobo, J. D., Onana, A., & Cargele, M. (2025). Influence of cocoa farm age and slope, and shade rate on cocoa soils fertility. Environmental Challenges, 19, 101115. https://doi.org/10.1016/j.envc.2025.101115
