Research shows that combining poultry litter with beneficial microorganisms can double zinc content and increase iron by 70% in orange-fleshed sweet potatoes while boosting crop yield 2.6 times, according to Gram Research analysis of field trials in Senegal. This agroecological approach uses locally available materials instead of chemical fertilizers, offering a sustainable way to address mineral deficiencies affecting millions of children and women in sub-Saharan Africa.
According to Gram Research analysis, scientists in Senegal discovered that combining organic waste products like poultry litter with beneficial microbes can dramatically increase iron and zinc levels in orange-fleshed sweet potatoes. In field tests conducted over two growing seasons, certain combinations more than doubled zinc content and boosted iron by 70%. This matters because sweet potatoes are already promoted in Africa to fight vitamin A deficiency, but they naturally contain low levels of these critical minerals. Using locally available organic materials and natural microbes instead of chemical fertilizers could help address mineral deficiencies affecting millions of children and women in sub-Saharan Africa while supporting sustainable farming.
Key Statistics
A 2026 field study in Senegal found that poultry litter combined with beneficial microorganisms increased zinc concentration to 20 mg per kilogram of dry matter—double the unfertilized control—while simultaneously boosting crop yield to 21 tons per hectare, a 2.6-fold increase.
According to research published in Food Science & Nutrition in 2026, adding mycorrhizal fungi to poultry litter and beneficial microbes increased iron concentration in orange-fleshed sweet potatoes to 44 mg per kilogram of dry matter, representing a 70% increase compared to unfertilized soil.
A 2026 Senegal-based study demonstrated that micronutrient deficiencies affect 42% of children under 5 years and 37% of women of reproductive age, and that agroecological fortification methods using organic waste products and microbial inocula can significantly improve mineral nutrition in staple crops.
Field experiments conducted across two contrasting seasons in Senegal showed that the combination of poultry litter with beneficial microorganisms and mycorrhizal fungi produced synergistic effects, with results varying significantly based on which specific organic materials and microbe types were used together.
The Quick Take
- What they studied: Whether combining organic waste materials (like poultry litter) with beneficial microorganisms could increase iron and zinc levels in orange-fleshed sweet potatoes grown in Senegal.
- Who participated: Field experiments conducted across two growing seasons (rainy and dry) in Senegal using the ‘Apomudem’ variety of orange-fleshed sweet potato, with multiple treatment combinations tested in replicated plots.
- Key finding: Poultry litter combined with beneficial microbes increased zinc to 20 mg per kilogram (double the control), while adding mycorrhizal fungi boosted iron to 44 mg per kilogram—a 70% increase. Crop yield also jumped 2.6 times higher.
- What it means for you: If you live in or work with communities in sub-Saharan Africa, this approach offers a low-cost, sustainable way to grow more nutritious sweet potatoes using materials already available locally. However, results may vary based on local soil conditions and climate.
The Research Details
Researchers conducted field experiments in Senegal during two contrasting growing seasons: a rainy season from June to November 2021, and a dry season from December 2021 to May 2022. They tested orange-fleshed sweet potatoes using different combinations of organic waste products (like poultry litter and other plant-based materials) mixed with two types of beneficial microorganisms: a bacterial-fungal consortium from fermented forest litter, and mycorrhizal fungi (a type of fungus that helps plants absorb nutrients).
The study used a factorial design, meaning researchers systematically tested different combinations of materials and microbes to see which worked best. Each treatment was replicated four times to ensure results were reliable. By testing across two different seasons, the researchers could see whether the benefits held up under different weather and growing conditions.
This approach mimics how farmers traditionally improve soil using local materials, but adds scientific measurement to identify which specific combinations work best for boosting iron and zinc.
This research design matters because it tests real-world farming conditions rather than just laboratory conditions. By conducting experiments across two different seasons, the researchers could see whether the benefits were consistent or varied with weather. Testing multiple combinations helped identify which specific materials and microbes work together most effectively. This practical approach means the findings are more likely to work for actual farmers in the region.
The study’s strengths include testing across two contrasting seasons, using replicated plots to ensure reliability, and measuring actual crop yield alongside nutrient content. The research was published in a peer-reviewed nutrition journal. However, the study doesn’t specify the exact number of plots tested or provide detailed statistical analysis in the abstract. Results may be specific to Senegal’s climate and soil conditions, so effectiveness in other regions would need separate testing.
What the Results Show
The most effective treatment combined poultry litter with beneficial microorganisms, producing 21 tons of sweet potatoes per hectare—more than 2.6 times the amount from unfertilized soil. This same combination doubled zinc concentration to 20 mg per kilogram of dry matter.
When researchers added mycorrhizal fungi (a helpful fungus) to poultry litter and beneficial microbes, iron concentration jumped to 44 mg per kilogram of dry matter—a 70% increase compared to the control. These results demonstrate that combining different organic materials with multiple types of beneficial microorganisms creates a synergistic effect, meaning they work better together than separately.
The benefits varied depending on which specific organic waste product and microbe combination was used, showing that not all combinations are equally effective. This suggests that farmers need to match their local materials and microbes to get the best results.
The study found that the effects of organic materials and microbes were season-dependent, with some combinations performing better during the rainy season and others during the dry season. This indicates that farmers may need to adjust their approach based on local weather patterns. The research also confirmed that the interactions between different materials and microbes were crucial—simply adding more materials didn’t guarantee better results unless the right combinations were used.
Orange-fleshed sweet potatoes have been widely promoted in sub-Saharan Africa primarily for their vitamin A content to address vitamin A deficiency. However, previous research has noted that these potatoes naturally contain low iron and zinc levels, limiting their ability to address mineral deficiencies. This study builds on that knowledge by demonstrating that agroecological methods can significantly enhance mineral content, offering a practical solution that previous research suggested was needed.
The study doesn’t specify the exact number of experimental plots or provide detailed statistical measures of uncertainty. Results are specific to Senegal’s climate and soil conditions, so the same combinations may not work equally well in other regions. The research doesn’t compare these organic methods directly to chemical fertilizers in terms of cost-effectiveness or long-term sustainability. Additionally, the study focuses on one sweet potato variety (‘Apomudem’), so results may differ for other varieties.
The Bottom Line
For farmers and agricultural programs in sub-Saharan Africa: Consider using poultry litter combined with beneficial microorganisms to boost both crop yield and mineral content in sweet potatoes. This approach is supported by field evidence and uses locally available materials. Confidence level: Moderate to High for the specific region tested (Senegal), but should be adapted to local conditions. For policymakers: This research supports investment in agroecological farming methods as a sustainable approach to addressing micronutrient deficiencies while improving food security.
This research is most relevant for: farmers and agricultural extension workers in sub-Saharan Africa growing sweet potatoes; public health programs addressing micronutrient deficiencies in children and women; agricultural policymakers promoting sustainable farming; and organizations working on food security in developing regions. The findings are less directly applicable to farmers in other climates without local adaptation testing.
Farmers could see increased crop yield within one growing season (3-6 months) after implementing these practices. Improvements in community nutrition would likely take longer—at least 6-12 months of regular consumption of the enriched sweet potatoes to measurably improve iron and zinc status in vulnerable populations.
Frequently Asked Questions
Can you increase iron and zinc in sweet potatoes without using chemical fertilizers?
Yes. Research from Senegal shows that combining poultry litter with beneficial microorganisms increased iron by 70% and doubled zinc content in orange-fleshed sweet potatoes. This agroecological approach uses locally available organic materials instead of synthetic fertilizers.
What’s the best way to boost mineral content in sweet potato crops?
A 2026 study found that poultry litter combined with beneficial microbes and mycorrhizal fungi produced the strongest results, increasing both yield and mineral concentrations. However, the most effective combination may vary depending on your local soil and climate conditions.
How much can organic fertilizers increase sweet potato yield?
Field trials in Senegal showed that poultry litter with beneficial microorganisms increased yield to 21 tons per hectare—2.6 times higher than unfertilized soil. Results varied by season and specific material combinations used.
Does this organic method work in all climates?
The research was conducted in Senegal across two seasons and showed consistent benefits, but results may vary in other regions. Local adaptation testing is recommended to identify which combinations work best for your specific climate and soil conditions.
How long does it take to see improvements in crop nutrition?
Increased yield appears within one growing season (3-6 months). However, measurable improvements in human nutrition would require several months of regular consumption of the enriched sweet potatoes.
Want to Apply This Research?
- If using an agricultural app: Track weekly soil amendments (type and amount of organic waste added), microbial inoculant application dates, and harvest yield and nutrient measurements. Compare results across seasons to identify the best combinations for your specific location.
- Start by collecting available organic waste materials (poultry litter, plant compost) and identifying local sources of beneficial microorganisms. Begin with a small test plot using the most effective combination (poultry litter + beneficial microbes) to see results before scaling up to larger areas.
- Over multiple growing seasons, maintain records of which material and microbe combinations produced the highest yields and nutrient levels in your specific conditions. Gradually refine your approach based on local results rather than assuming all combinations will work equally well in your area.
This research describes agricultural practices tested in Senegal and may not produce identical results in other regions without local adaptation. These findings are intended to inform agricultural practices and food security initiatives, not to replace medical treatment for iron or zinc deficiency. Individuals with diagnosed mineral deficiencies should consult healthcare providers for appropriate treatment. While this study demonstrates promising results for crop enrichment, actual nutritional improvements in people depend on consistent consumption of these enriched foods as part of a balanced diet. Agricultural extension services should conduct local trials before recommending these practices to farmers in new regions.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.
