Complete Guide: How Many Bags of Potato Seeds Per Acre in Kenya

Quick Answer

One acre of potato farming in Kenya requires 15-25 bags of seed potatoes (50kg bags), equivalent to 750-1,250kg of seed tubers. The standard recommendation is 18-22 bags (900-1,100kg) per acre using medium-sized tubers (45-55g each) at standard spacing (75cm between rows, 30cm between plants). This plants approximately 17,778 seed pieces per acre.

Close spacing (60cm x 25cm): 27-30 bags/acre (higher yield potential, higher seed cost)
Standard spacing (75cm x 30cm): 18-22 bags/acre (recommended balance)
Wide spacing (90cm x 35cm): 13-16 bags/acre (lower seed cost, easier mechanization)

Factors Affecting Seed Potato Requirements

1. Plant Spacing

Spacing is the primary factor determining how many seed potatoes you need. The standard recommendation in Kenya is 75cm between rows and 30cm between plants, giving approximately 17,778 planting positions per acre. This spacing allows adequate soil for hilling (earthing up), good air circulation to reduce disease pressure, and space for mechanical cultivation if used.

Standard Spacing Calculation:

Acre size: 4,047 square meters
Row spacing: 75cm (0.75m)
Plant spacing: 30cm (0.30m)
Plants per acre: 4,047 ÷ (0.75 × 0.30) = 17,978 positions
Practical figure: ~17,778 (accounting for headlands)

2. Seed Tuber Size

Seed tuber size directly affects how many bags you need. Larger tubers mean more weight per planting position, thus more bags required. The recommended seed size is 45-55g (egg-sized), which provides good plant vigor while being economical.

Seed Size Impact:

Small (30-40g): 12-15 bags/acre - Economical but may produce weaker plants with fewer stems
Medium (45-55g): 18-22 bags/acre - Optimal balance of cost and plant vigor (RECOMMENDED)
Large (65-80g): 24-30 bags/acre - More expensive, but can be cut to halve seed cost

3. Cutting Large Tubers

Large seed tubers (over 60g) can be cut into 2-3 pieces to reduce seed costs by 40-60%. Each piece must have at least one well-developed eye (sprout). Cut 2-3 days before planting to allow cut surfaces to heal (suberize), and treat with fungicide (Ridomil MZ or Mancozeb) to prevent rot.

⚠️ Warning: Bacterial Wilt Risk

Cutting seed potatoes can spread bacterial wilt (Ralstonia solanacearum) if contaminated tubers are cut. Always sterilize cutting tools with 10% bleach solution between tubers. Discard any tubers showing brown vascular discoloration when cut. In bacterial wilt-prone areas, use whole tubers only.

Certified vs. Farm-Saved Seed: Economic Analysis

Case Study: Nyandarua Farmer Comparison

A 2024 study by the National Potato Council of Kenya compared yields between farmers using certified seed versus farm-saved seed in Nyandarua County. The results demonstrate the economic advantage of certified seed despite higher upfront costs:

Factor	Certified Seed (Shangi)	Farm-Saved Seed (3rd Gen)
Seed Cost/Acre	KSh 90,000 (20 bags @ KSh 4,500)	KSh 60,000 (20 bags @ KSh 3,000)
Yield Achieved	310 bags/acre	195 bags/acre
Revenue (@ KSh 3,500)	KSh 1,085,000	KSh 682,500
Other Costs	KSh 180,000	KSh 180,000
Net Profit	KSh 815,000	KSh 442,500
Profit Difference	+KSh 372,500 per acre with certified seed

Despite the KSh 30,000/acre higher seed cost, the farmer using certified seed earned KSh 372,500 more profit per acre - a return of 12x on the additional seed investment. This demonstrates why the National Potato Council recommends certified seed for all commercial potato production.

Why Farm-Saved Seed Declines

Potato is vegetatively propagated, meaning diseases accumulate in seed tubers over generations. Each generation of farm-saved seed typically loses 10-15% yield potential due to:

Viral diseases: Potato virus Y (PVY), Potato leaf roll virus (PLRV) spread by aphids
Bacterial wilt: Ralstonia solanacearum persists in soil and infected tubers
Varietal degeneration: Off-types and mutations accumulate
Physiological aging: Repeated generations reduce vigor

After 3-4 generations, farm-saved seed typically yields 40-50% less than certified seed of the same variety. This is why KALRO recommends purchasing certified seed at least every 3 generations.

Pre-Planting Seed Preparation

Chitting (Pre-Sprouting)

Chitting is the process of encouraging seed potatoes to develop short, sturdy sprouts before planting. This reduces time to emergence by 7-14 days and improves uniformity. Place seed tubers in single layers in diffused light (not direct sunlight) at 15-20°C for 2-4 weeks before planting.

Ideal Chitting Conditions:

Temperature: 15-20°C (cool room or shed)
Light: Diffused natural light (not dark, not direct sun)
Duration: 2-4 weeks before planting
Target sprouts: 1-2cm long, green, sturdy (not white/elongated)
Arrangement: Single layer, eye-end up, in trays or on floor

Seed Treatment

Treating seed potatoes with fungicide protects against soil-borne diseases during emergence. This is especially important for cut seed or when planting in cool, wet conditions that favor rot.

Product	Active Ingredient	Rate	Target Diseases
Ridomil Gold MZ	Metalaxyl + Mancozeb	50g/20L water (dip)	Late blight, Pythium
Mancozeb 80WP	Mancozeb	Dust cut surfaces	Fusarium, Rhizoctonia
Maxim XL	Fludioxonil + Mefenoxam	100ml/100kg seed	Rhizoctonia, seed rot

Potato Varieties and Seed Requirements

Popular Varieties in Kenya

1. Shangi (Most Popular)

Expected Yield: 250-350 bags/acre
Maturity: 90-100 days
Tuber: Cream skin, cream flesh, oblong
Market: Premium prices, high demand
Seed Rate: 20 bags/acre (standard spacing)
Strength: Excellent cooking quality, fast cooking
Weakness: Susceptible to late blight

2. Tigoni (Highest Yielder)

Expected Yield: 300-400 bags/acre
Maturity: 100-120 days
Tuber: White skin, white flesh, round-oval
Market: Good demand, slightly below Shangi price
Seed Rate: 20 bags/acre (standard spacing)
Strength: High yield, late blight resistant
Weakness: Longer maturity period

3. Kenya Mpya (Red Skin)

Expected Yield: 200-300 bags/acre
Maturity: 90-100 days
Tuber: Red skin, yellow flesh
Market: Premium in Western Kenya
Seed Rate: 20 bags/acre
Strength: Good storage, disease resistant
Weakness: Lower yield than Shangi

4. Unica (Heat Tolerant)

Expected Yield: 200-300 bags/acre
Maturity: 90-100 days
Tuber: Red skin, cream flesh
Market: Good for processing (chips)
Seed Rate: 20 bags/acre
Strength: Heat tolerant, good for lower altitudes
Weakness: Limited seed availability

Frequently Asked Questions (FAQs)

Q1: How many bags of potato seeds do I need for 1 acre?

You need 18-22 bags (50kg each) of seed potatoes per acre using medium-sized tubers (45-55g) at standard spacing (75cm x 30cm). This equals 900-1,100kg of seed, providing approximately 17,778 seed pieces per acre.

Q2: What is the cost of potato seed per acre in Kenya?

Certified seed costs KSh 70,000-100,000 per acre (18-22 bags @ KSh 3,500-4,500/bag). Farm-saved seed costs KSh 50,000-65,000/acre but yields 30-50% less. The extra KSh 30,000 for certified seed typically returns KSh 200,000-400,000 in additional yield.

Q3: Where can I buy certified potato seed in Kenya?

Certified seed is available from KEPHIS-registered multipliers: ADC Molo (Nakuru), Kisima Farm (Meru), KALRO Tigoni (Kiambu), and farmer cooperatives in Nyandarua and Elgeyo Marakwet. Order 2-3 months before planting as demand exceeds supply during peak seasons.

Q4: Can I cut large seed potatoes to reduce costs?

Yes, tubers over 60g can be cut into 2-3 pieces, each with at least one eye. Cut 2-3 days before planting, treat with fungicide, and allow surfaces to heal. This reduces seed cost by 40-60%. However, avoid cutting in bacterial wilt-prone areas as it spreads disease through contaminated tools.

Q5: What is the best seed size for potato planting?

Medium-sized tubers (45-55g) are recommended - they balance cost with plant vigor. Small tubers (30-40g) are cheaper but produce weaker plants. Large tubers (65-80g) produce vigorous plants but cost more unless cut.

Q6: How long should I chit (pre-sprout) seed potatoes?

Chit seed potatoes for 2-4 weeks in diffused light at 15-20°C. Target short, green, sturdy sprouts 1-2cm long. Avoid dark storage that produces long white sprouts (easily broken) or warm storage that ages seed prematurely.

Q7: How many times can I recycle potato seed?

You can save seed for maximum 2-3 generations after purchasing certified seed. Each generation loses 10-15% yield potential due to disease accumulation. After 3 generations, buy fresh certified seed to restore yields.

Q8: What spacing gives the highest potato yield?

Close spacing (60cm x 25cm) gives highest yield per acre but costs 50% more in seed. Standard spacing (75cm x 30cm) is recommended for the best balance of yield, seed cost, and disease management. Wide spacing (90cm x 35cm) is economical but may reduce total yield.

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