Potatoes have become one of the most versatile and profitable crops in Central Africa, yet many smallholder farmers still battle erratic yields and undersized tubers. In the volcanic highlands around Santa, Cameroon, the Santa Potato Farmers’ Co-operative has embraced an uncomplicated—but highly effective—practice known as stem reduction. By limiting the number of shoots that emerge from each seed tuber, growers are dramatically increasing both tuber size and overall yield. This article explores the science behind stem reduction, chronicles the co-operative’s on-farm results, and outlines opportunities for partners who share a vision of sustainable, scalable African agriculture.
The Santa Highlands: Climate, Soils, and Market Pressures
Perched between 1 ,800 m and 2 ,100 m above sea level, Santa enjoys a cool subtropical climate (average 15 °C–23 °C) and deep, friable Andosols created by Mount Cameroon’s ancient ash deposits. These volcanic soils are rich in organic matter but prone to nutrient leaching during the seven-month wet season. Potatoes slip neatly into the region’s two annual planting windows—early March and late August—yet farmers often struggle to meet rising urban demand because rainfall, pests, and declining seed quality conspire to erode profit margins.
What Is Stem Reduction?
A single potato “seed” tuber can sprout anywhere from three to ten stems (shoots). Stem reduction is the deliberate removal of surplus stems—usually leaving two or three—shortly after emergence (when shoots are 8 – 12 cm tall). The practice:
- Reduces intra-plant competition. Fewer stems mean fewer developing tubers vying for the plant’s finite photosynthate supply.
- Channels assimilates into fewer sinks. Remaining tubers grow larger and more uniform, commanding better market prices.
- Improves canopy aeration. Thinner foliage dries faster after rain, suppressing early blight (Alternaria solani) and late blight (Phytophthora infestans).
- Simplifies crop management. Ridging, hilling, and targeted pesticide applications become more precise when stems are fewer and evenly spaced.
Methodology on the Co-operative’s Trial Plots
| Parameter | Conventional Practice | Stem-Reduction Protocol |
|---|---|---|
| Seed rate | 2 t ha⁻¹ | 2 t ha⁻¹ |
| Avg. stems per plant | 6–7 | 2–3 (excess stems pinched at 10 days after emergence) |
| Fertility | 90 kg ha⁻¹ N : 60 kg P₂O₅ : 90 kg K₂O | Same |
| Plant spacing | 75 cm × 30 cm | Same |
| Irrigation | Rain-fed | Rain-fed |
Data from 2022-2024 trials (mean of six replications):
- Marketable yield rose from 19.4 t ha⁻¹ to 24.8 t ha⁻¹ (↑ 28 %).
- Mean tuber diameter increased from 48 mm to 62 mm.
- Grade-out losses (undersized or misshapen tubers) fell by 34 %.
- Late-blight incidence dropped from 22 % to 13 %, cutting fungicide costs by one spray per season.
Why It Works: The Physiology in Brief
Potato plants set tubers on underground stolons originating from each above-ground stem. A high stem count forces the plant to partition carbohydrates across dozens of developing tubers; final tuber size is therefore capped by the weakest source–sink pathway. By pruning stems early, growers re-balance the plant’s internal allocation: the same photosynthetic area services fewer tuber sinks, so each tuber gains more assimilates per unit time. Research from CIP (International Potato Center) corroborates that optimal stem density for ware-potato production is two to four stems per plant in temperate zones; Santa’s subtropical conditions follow a similar curve.
Practical Tips for Implementation
- Start with vigorous, well-sprouted seed. Cut seed pieces 100 g in size, containing one dominant eye.
- Plant on deep, loose ridges. A 20 cm furrow depth protects stolons from sunlight greening.
- Reduce stems at 8 – 12 cm height. Thumb-and-forefinger pinching is faster than scissors; disinfect hands between rows to curb bacterial wilt.
- Fertility must keep pace. Fewer stems still need ample nitrogen and potassium; split-apply N at 30 % planting / 70 % at hilling.
- Monitor spacing. If stems are reduced, do not compensate by over-planting; ideal canopy closure remains 40 – 45 days after emergence.
Economic and Social Impact
- Higher farm-gate price. Premium hotels in Douala offer a 15 % bonus for tubers exceeding 55 mm.
- Labour equity. Stem reduction is light work, easily done by women and youth, distributing income across households.
- Climate resilience. Improved aeration lessens fungicide dependence, lowering environmental load on hillside watersheds.
Challenges and Mitigation
| Challenge | Mitigation |
|---|---|
| Extra field pass required | Combine stem pruning with the first urea top-dressing to save labor. |
| Risk of pathogen entry through fresh wounds | Remove stems in the morning when humidity is lower; disinfect hands with 1 % bleach solution every bed. |
| Resistance from tradition-minded growers | Run side-by-side demonstration plots; yield differences speak louder than lectures. |
Scaling Up: An Invitation to Collaborate
The co-operative is poised to expand from 25 ha to 60 ha within three seasons but requires:
- Cold-store investment to reduce post-harvest losses (currently 18 %).
- Tissue-culture seed production to guarantee disease-free starter tubers.
- Export-compliant packaging lines for regional supermarkets in Lagos and Abidjan.
We welcome agribusiness investors, NGOs, research institutes, and technology providers who can co-design inclusive, profitable potato value chains.
Contact
Ngukong Paul Fonanjei
fonanjeipaul@gmail.com | +237 674 836 041 | WhatsApp +237 670 097 795
Conclusion
Stem reduction epitomizes the kind of low-cost, high-impact innovation that can push African potato farming beyond subsistence and into competitive regional trade. Santa’s volcanic soils and cool misty mornings already provide the perfect terroir; with a few well-timed pinches per plant, farmers are harnessing that natural advantage to feed—and prosper in—an increasingly potato-loving world.
