Cassava Yield Per Hectare: Planting Density and Tuber Weight
Introduction
Cassava (Manihot esculenta), also called manioc or yuca, is the third most important source of calories in the tropics after rice and maize, feeding more than 800 million people. Nigeria is the world's largest producer, followed by Thailand, Indonesia, and Brazil. Yet average yields in smallholder systems across sub-Saharan Africa remain stubbornly low at 8–12 tonnes per hectare, compared with 20–30 t/ha in Thailand and 25–35 t/ha under best-management practices. The gap is not genetic — it is agronomic.
This article explains how cassava yield is determined by three multiplicative factors: plant population (density), number of marketable tubers per plant, and average tuber weight. We provide the yield formula, benchmark ranges for major producing regions, worked examples for Nigeria and Thailand, and the specific management practices that drive each component.
Yield Components and the Formula
Cassava yield is the product of three components, each influenced by different management decisions:
- Plant population (plants/ha) — determined by spacing. Common spacings: 1 m × 1 m = 10,000 plants/ha; 1 m × 0.8 m = 12,500; 0.8 m × 0.8 m = 15,625; 1.2 m × 0.8 m = 10,417. Optimal density is 10,000–15,000 plants/ha depending on variety branching habit and soil fertility.
- Marketable tubers per plant — typically 5–12 tubers, of which 3–8 are marketable (>100 g each). Affected by variety, stem cutting quality, weed control, and disease (especially cassava mosaic disease and brown streak disease).
- Average tuber weight — ranges from 0.3 kg to 1.5 kg per tuber depending on variety, growing period, and fertility. Long-season varieties (12–14 months) produce larger tubers than short-season (8–10 months).
The yield formula:
Fresh tuber yield (t/ha) = (Plants/ha × Tubers/plant × Avg tuber weight kg) ÷ 1000
Adjust for plant survival rate (typically 80–95%): multiply by survival %.
Dry matter content is 30–35% for most varieties; starch content is 25–32% of fresh weight. For processing into gari, fufu, or starch, dry matter yield is the more relevant metric: DM yield (t/ha) = Fresh yield × DM%.
Regional Benchmark Yields
| Region/System | Plants/ha | Tubers/plant | Avg tuber (kg) | Yield (t/ha) |
|---|---|---|---|---|
| Nigeria smallholder, no inputs | 8,000–10,000 | 3–5 | 0.3–0.5 | 8–15 |
| Nigeria improved (TMS varieties + fertilizer) | 12,500 | 6–8 | 0.5–0.8 | 25–40 |
| Thailand commercial (Rayong varieties) | 12,500–15,625 | 6–10 | 0.5–0.9 | 20–30 |
| Brazil cerrado, mechanized | 10,000–12,500 | 7–10 | 0.6–1.0 | 25–35 |
Worked Example 1: Smallholder Farm, Oyo State, Nigeria
Variety: TMS 30572 (improved, mosaic-resistant). Spacing: 1 m × 1 m = 10,000 plants/ha. Survival: 85% (some stem cutting failure and mosaic disease). Harvest at 12 months. Average 5.5 marketable tubers/plant, average tuber weight 0.55 kg. NPK 15-15-15 applied at 200 kg/ha at 8 weeks after planting.
Calculation:
Effective plant population: 10,000 × 0.85 = 8,500 plants/ha.
Tubers per ha: 8,500 × 5.5 = 46,750 tubers.
Total weight: 46,750 × 0.55 kg = 25,713 kg = 25.7 t/ha fresh tubers.
At 32% dry matter: 8.2 t/ha DM.
At a farm-gate price of ₦150,000/tonne (~$190/t), gross revenue = $4,883/ha.
Without fertilizer and with a local variety, the same farmer might achieve 3.5 tubers/plant at 0.35 kg = 10.4 t/ha — a 60% yield gap. The $50 fertilizer investment generates an additional $2,900 in revenue.
Worked Example 2: Commercial Farm, Khon Kaen, Thailand
Variety: Rayong 9 (high starch, early maturity). Spacing: 0.8 m × 0.8 m = 15,625 plants/ha. Survival: 95% (mechanized planting, quality stem cuttings). Harvest at 10 months. Average 7.2 marketable tubers/plant, average tuber weight 0.65 kg. Fertilizer: 300 kg/ha 16-16-8 formula at planting + 150 kg/ha urea at 2 months.
Calculation:
Effective population: 15,625 × 0.95 = 14,844 plants/ha.
Tubers/ha: 14,844 × 7.2 = 106,877.
Total weight: 106,877 × 0.65 = 69,470 kg = 69.5 t/ha — this is high but within the range for top Thai producers with full irrigation and fertilization. More typical commercial yields are 25–35 t/ha; this example represents an exceptional field.
Realistic adjusted estimate (accounting for non-marketable tubers and harvest losses at 15%): 69.5 × 0.85 = 59 t/ha. At 30% starch content and a starch factory price of $45/t fresh root, gross revenue = $2,655/ha.
Management Practices That Drive Yield
Planting material: Use mature, disease-free stem cuttings (20–25 cm long, 4–6 nodes) from the middle portion of the stem. Cuttings from the top or bottom produce weaker plants. Treat with insecticide/fungicide if cassava mealybug or mosaic disease is present.
Weed control: Cassava is slow to establish and poor at competing with weeds in the first 8–12 weeks. Two manual weedings or a pre-emergence herbicide (atrazine + metolachlor) can increase yield by 30–50% compared with unweeded plots.
Fertility: Cassava responds well to N and K, less to P. A typical recommendation is 60–80 kg N/ha, 40–60 kg P₂O₅/ha, and 80–120 kg K₂O/ha. Apply N and K split: half at planting/early growth, half at 2–3 months. Avoid excessive N late in the season, which promotes top growth at the expense of tubers.
Harvest timing: Tuber bulking accelerates from 4–5 months and continues until 10–14 months. Harvesting too early (6–7 months) sacrifices 30–50% of potential yield. However, delaying beyond 14 months increases woodiness and post-harvest physiological deterioration (PPD), which reduces processing quality.
Common Mistakes to Avoid
1. Planting too densely. Above 15,000 plants/ha, interplant competition reduces tuber size and increases lodging. Optimal is 10,000–13,000 for branching varieties, 12,000–15,000 for non-branching.
2. Using poor-quality stem cuttings. Old, thin, or diseased cuttings reduce survival by 20–40% and produce weak plants. Always select from healthy, high-yielding mother plants.
3. Delayed weeding. Weed competition in the first 12 weeks can reduce yield by 40–60%. Weed at 4, 8, and 12 weeks after planting, or use pre-emergence herbicide.
4. Ignoring pest and disease. Cassava mosaic disease (CMD) can reduce yield by 20–90%. Use resistant varieties (TMS series in Nigeria, KU50 in Thailand) and rogue infected plants early.
5. Not adjusting for survival rate. Always multiply plant population by actual survival (80–95%). Assuming 100% survival overestimates yield by 5–20%.
Conclusion
Cassava yield is straightforward to calculate: plants per hectare × marketable tubers per plant × average tuber weight, adjusted for survival. The global yield gap — 8–12 t/ha for African smallholders vs. 25–35 t/ha for best practices — is closed primarily through improved varieties, quality stem cuttings, timely weeding, and balanced fertilization. For most tropical smallholders, moving from 10 t/ha to 20 t/ha requires no new machinery, only better agronomy. Calculate your potential yield, identify which component is most limiting, and target that component first.
Use our Cassava Yield Calculator to estimate yield from your planting density and tuber measurements.