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How to Grow Sunflowers: A Guide for Farmers

How to Grow Sunflowers: A Guide for Farmers

Sunflowers are one of the most important oilseed crops in Southern Africa, valued for their high oil content, which is used in cooking oil and margarine production. The by-product, sunflower cake, is also an excellent livestock feed. Sunflowers are a low-input crop, making them ideal for marginal areas and small-scale farmers. This guide will walk you through everything you need to know to successfully grow sunflowers, from soil preparation to harvesting.

Why Grow Sunflowers?

  • High Oil Content: Modern hybrid varieties have up to 40% oil content.
  • Versatility: Sunflowers can be grown in both rain-fed and irrigated conditions.
  • Short Growing Period: Sunflowers mature in just 90 days, making them an excellent catch crop if your main crop fails.
  • Drought Tolerance: Sunflowers are more drought-resistant than many other grain crops, making them suitable for marginal areas.

Climatic and Soil Requirements

Climate

  • Sunflowers thrive in marginal areas with moderate rainfall.
  • They are drought-tolerant but respond well to irrigation, especially during the pollination period.
  • The crop can be grown as a winter irrigated crop in frost-free areas.

Soil

  • Ideal Soil: Deep, well-drained loam soils with good physical conditions.
  • Soil pH: Sunflowers are sensitive to acidic soils. The optimal pH is 5.3 (calcium chloride scale). If the pH is below 5.0, apply lime to correct it.
  • Avoid Nematodes: Sunflowers are prone to root-knot nematodes, so avoid planting them in light-textured soils where nematodes are common. Heavier soils are preferred.

Crop Rotation

  • Rotation Period: Do not plant sunflowers on the same land more than once every three years to prevent disease buildup.
  • Avoid: Do not rotate sunflowers with other Sclerotinia-susceptible crops like potatoes, soybeans, groundnuts, or common beans.
  • Good Rotation Crops: Maize and grain sorghum are excellent rotation crops for sunflowers.

Recommended Varieties

  • Early Maturing Varieties: G.100, G.101, and SNK.37 (90–110 days).
  • Mid-Season Varieties: Perodovik, Mopani, and Msasa (76–96 days).
  • Long-Season Varieties: PNR.7371 and Pan 7351 (115–120 days).

Always consult your local seed merchant for the latest hybrid varieties with high oil content and disease resistance.

Planting Guidelines

Planting Date

  • Rain-Fed Crops: Mid to late December is the optimal planting time.
  • Irrigated Crops: In frost-free areas, planting can extend until February or March.

Seed Rate and Spacing

  • Seed Rate: 4–6 kg of treated seed per hectare.
  • Spacing:
    • Irrigated Crops: 55,000 plants/ha (20–37 cm in-row spacing, 90 cm between rows).
    • Rain-Fed Crops: 40,000–45,000 plants/ha in areas with reliable rainfall.
    • Dry Areas: 30,000 plants/ha in areas with unreliable rains.

Planting Depth

  • Plant seeds at a uniform depth of 5 cm, but no deeper than 7 cm or shallower than 3 cm.

Fertilization

  • Boronated Fertilizer: Essential for sunflower growth. Apply a boronated compound fertilizer (e.g., Cottonfert 5:17:10 with 0.25% boron) at 250–300 kg/ha, banded at planting.
  • Top-Dressing: Apply Ammonium Nitrate at 150–300 kg/ha six weeks after planting, depending on rainfall and irrigation.
  • Micronutrients: If soil analysis shows low molybdenum levels, apply a foliar spray of Sodium Molybdate at 100 g/100 L water.

Weed Control

  • Critical Period: Sunflowers are poor weed competitors, so keep the field weed-free for the first 6–8 weeks.
  • Herbicides:
    • Trifluralin: Pre-planting herbicide for annual grasses.
    • Lasso®: Post-planting herbicide for grasses and some broadleaf weeds.
    • Fusilade Super®: Controls emerged grasses.
    • Gesagard®: Controls broadleaf weeds (use in combination with a grass killer).
  • Avoid Atrazine: Sunflowers are highly sensitive to Atrazine residues, which can cause damage even two years after application.

Pest Management

Common Pests

  1. Root-Knot Nematodes: Avoid planting in light soils and practice long crop rotations.
  2. White Grubs/False Wireworms: Use Dursban® 4 E at 1.0 L/ha in the planting row.
  3. Cutworms: Keep the field weed-free and apply Karate® at 100 ml/ha.
  4. Bollworms: Use Thionex® 35 EC at 650 ml/200 L water/ha (not within 21 days of harvest).
  5. Aphids: Apply Rogor® 40 CE at 750 ml/ha or Metasystox® 25 EC at 500 ml/ha.

Disease Management

Common Diseases

  1. Septoria Leaf Spot: Caused by water splash. Manage by avoiding overhead irrigation.
  2. Rust: Common in hot, humid conditions but rarely serious.
  3. Sclerotinia Wilt and Head Rot: Potentially devastating. Practice long rotations and remove diseased plants.
  4. Bacterial Wilt: Severe but rare. Avoid planting in fields with a history of bacterial wilt in tomatoes or potatoes.

Irrigation

  • Sunflowers are drought-tolerant but respond well to irrigation, especially during the 30-day pollination period.
  • For winter crops, apply 80–85% of the water used for wheat.

Harvesting

  • Combine Harvesting: Use a combine harvester with sunflower attachments when moisture content is around 20%.
  • Hand Harvesting: Cut heads when the backs are yellow and dry them on the ground. Thresh using a maize sheller at half the drum speed used for maize.

Key Takeaways

  • Sunflowers are a low-input, high-reward crop suitable for marginal areas.
  • Proper weed control and soil preparation are critical in the early stages.
  • Use boronated fertilizers and practice long crop rotations to avoid diseases and nematodes.
  • Always read chemical labels before application and follow recommended guidelines.

 

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