FERTILIZING CASSAVA FOR ROOT BULKING – SUPPORTING LARGER ROOTS AND HIGHER STARCH CONTENT

Fertilizing cassava for root bulking at the right stage supports root development, Potassium (K) supply, and higher starch accumulation.

Fertilizing cassava for root bulking at the right stage

Around 55–60 days after planting, when the cassava canopy begins to close and the roots have differentiated into young storage roots, the crop enters an important stage of root development and starch accumulation.

At this stage, fertilizing cassava for root bulking should focus on supplying sufficient Potassium (K) to support nutrient transport and accumulation in the roots, while keeping Nitrogen (N) at an appropriate level so the foliage can continue photosynthesis without excessive vegetative growth.

This is also an important period to increase cassava starch content as the crop gradually shifts from vegetative growth toward storage root development.

Signs that indicate the right time for fertilizing cassava for root bulking

Farmers can monitor the following signs:

• The canopy begins to close: Stems and leaves are relatively well developed, and neighboring plant canopies start to overlap.
• Young storage roots have formed: The root system has clearly differentiated into storage roots and begins increasing in diameter.

When these signs appear, farmers can choose a suitable fertilizing cassava for root bulking program according to soil fertility and field conditions.

Option 1: NPK CON CO 20-20-15 AVS Gold combined with Potassium Chloride (KCl)

For gray degraded soils, sandy loam soils, nutrient-poor soils, or fields where cassava has been continuously cultivated for several seasons, farmers may consider:

• NPK CON CO 20-20-15 AVS Gold: 150 kg/ha.
• Potassium Chloride (KCl): 50–60 kg/ha.

NPK CON CO 20-20-15 AVS Gold supplies Nitrogen (N), Phosphorus (P), Potassium (K), and micronutrients, helping provide nutrients for foliage, roots, and storage root development.

The product is manufactured with AVS technology, supplying nutrients according to crop requirements during different growth stages.

Additional Potassium Chloride (KCl) increases the Potassium (K) supply, supporting nutrient transport and accumulation in storage roots. This fertilizing cassava for root bulking option can be considered for soils where nutrients are more susceptible to leaching.

Option 2: NPK CON CO 17-7-17+0.15Zn+0.1B

On ferrallitic soils, red basalt soils, or light- to medium-textured soils with relatively good fertility, farmers may consider NPK CON CO 17-7-17+0.15Zn+0.1B.

Reference application rate: 200–250 kg/ha.

Nutritional benefits include:

• Potassium (K) 17%: Supports nutrient transport and accumulation in storage roots, contributing to more uniform root development and helping increase cassava starch content.
• Nitrogen (N) 17%: Helps maintain healthy foliage for continued photosynthesis during the root bulking stage.
• Zinc (Zn) 0.15% and Boron (B) 0.1%: Supply essential micronutrients that support physiological and metabolic processes.

NPK CON CO 17-7-17+0.15Zn+0.1B is a suitable option for fertilizing cassava for root bulking where soil fertility is relatively good and the crop needs to maintain a balance between foliage activity and storage root development.

Fertilization practices to reduce nutrient losses

To improve the efficiency of fertilizing cassava for root bulking, farmers should consider the following practices:

• Control weeds before fertilization: Helps reduce competition for water and nutrients.
• Apply fertilizer in the right position: Place fertilizer along rows, furrows, or holes approximately 15–20 cm away from the plant base.
• Apply when soil moisture is suitable: Prefer early morning or late afternoon and avoid fertilizing immediately before heavy rainfall.
• Combine with earthing up: Particularly on gray degraded or sandy soils, earthing up after fertilization can help reduce nutrient losses and maintain loose soil conditions for storage root development.

Proper fertilization practices help improve nutrient use efficiency, support storage root development, and contribute to efforts to increase cassava starch content.

Supplementing cassava foliar fertilizer from months 3–5

In addition to soil fertilization, farmers may consider cassava foliar fertilizer products rich in Potassium (K) and supplemented with Boron (B) and Zinc (Zn), such as:

• KALIBO
• COFOLI K300
• SUPER TAN ĐỎ

Reference frequency: Apply 1–2 times at intervals of approximately 15–20 days, depending on actual crop growth and product label recommendations.

These cassava foliar fertilizer products provide additional Potassium (K), Boron (B), and Zinc (Zn), helping support nutrient transport to storage roots and maintain physiological activity in the foliage and root zone.

Combining soil fertilization with cassava foliar fertilizer can help farmers manage fertilizing cassava for root bulking more effectively during this stage.

Important considerations during the root bulking stage

During fertilizing cassava for root bulking, farmers should avoid excessive Nitrogen (N), as the crop may invest more heavily in stems and leaves instead of nutrient accumulation in storage roots.

During the dry season, fields should also be regularly monitored for mealybugs and red spider mites, with registered crop protection products used according to label instructions when necessary.

Application rates for NPK CON CO 20-20-15 AVS Gold, Potassium Chloride (KCl), and NPK CON CO 17-7-17+0.15Zn+0.1B should be adjusted according to variety, planting density, soil fertility, weather conditions, and actual crop growth.

Appropriate nutrient management during this stage contributes to storage root development and can help increase cassava starch content.

Conclusion

Fertilizing cassava for root bulking at the right stage and according to soil conditions helps maintain healthy foliage, provide Potassium (K) for storage root development, and support efforts to increase cassava starch content. Farmers should select fertilizer formulas and application rates based on actual field conditions.