Cowpea (Vigna radiata) is a common vegetable whose growth cycle greatly benefits from foliar fertilization. Foliar absorption of nutrients is rapid and efficient, making the selection of appropriate fertilizers critical to improving yield and quality. Below are recommended foliar fertilizers and application guidelines for cowpea.

1. Potassium Dihydrogen Phosphate (KH₂PO₄)

Function: Enhances plant growth, disease resistance, and yield. Application:

• Early growth stage: Apply 500 g per mu, diluted with water and sprayed evenly on both leaf surfaces.
• Frequency: Every 7–10 days, repeated 2–3 times. Notes:
• Avoid overapplication to prevent reduced taste.
• Apply on sunny days for better absorption.

2. Micronutrient Fertilizers (e.g., Boron, Zinc)

Function: Supports root development, stress resistance, and pest prevention. Application:

• Early growth: Spray boron fertilizer.
• Flowering/fruiting: Spray zinc fertilizer.
• Dose: 500 g per mu, diluted and sprayed biweekly (2–3 times). Notes:
• Balance with major nutrients to avoid imbalance.
• Apply on sunny days.

3. Amino Acid-Based Fertilizers (e.g., Urea, Calcium Nitrate)

Function: Provides nitrogen for growth and yield improvement. Application:

• Early growth: 500 g per mu, diluted and sprayed biweekly (2–3 times). Notes:
• Combine with other nutrients to prevent imbalance.
• Apply on sunny days.

4. Organic Fertilizers

Function: Improves soil structure and organic matter content. Application:

• Early growth: Spread 500 kg per mu, then incorporate into soil. Notes:
• Use alongside chemical fertilizers for balance.
• Apply on sunny days.

5. Water-Soluble Fertilizers

Function: Rapid absorption via foliage, boosting nutrient efficiency. Application:

• Early growth: 500 g per mu, diluted and sprayed biweekly (2–3 times). Notes:
• Avoid overapplication to maintain quality.
• Apply on sunny days.

6. Foliar Fertilizer Specialty Formulations

Function: Rapid nutrient replenishment and enhanced photosynthesis. Application:

• Follow dilution instructions, spraying leaf surfaces biweekly (2–3 times). Notes:
• Avoid overuse to preserve taste.
• Apply on sunny days.

General Guidelines

1. Tailor to Growth Stage: Match fertilizer type/concentration to plant needs and soil conditions.
2. Monitor Results: Adjust strategies if abnormalities arise.
3. Rotate Fertilizers: Prevent soil salt buildup or excess nutrients.
4. Frequent, Light Applications: Avoid overwhelming plants.
5. Weather Considerations: Apply on dry, sunny days to prevent loss or disease.
6. Post-Application Watering: Aids nutrient absorption.
7. Irrigation Adjustment: Ensure adequate moisture after fertilization.
8. Avoid Repetition: Do not apply the same fertilizer excessively in one area.
9. Timely Rain Protection: Steer clear of rainy/humid conditions.
10. Observe Plant Response: Fine-tune practices based on results.

(Note: The original text included repetitive precautions, which have been consolidated here for clarity while retaining all key points.)