Vegetable Growing

1. Importance of Vegetables

Vegetables are vital for:

• Nutrition: Rich source of vitamins (A, B, C, K, E) and minerals (iron, calcium, phosphorus, iodine, sodium, potassium).
• Income: Provide revenue through sales for farmers and traders.
• Employment: Create jobs in farming and related agro-trade.

2. Classification of Vegetables

Vegetables are classified into:

• Indigenous Vegetables: (e.g., Bonongwe – Amaranthus thunbergii, Luni – Gynandropsis, Denje – Corchorus trilocularis, Pumpkins, Mpiru – local mustard – Brassica juncea, Mnthwani – Cucurbita maxima, Chitambe – Vigna unguiculata, Khwanya – Phaseolus vulgaris, Limanda – Hibiscus acetosella, Chisoso/Kazota – black jack – Bidens pilosa, Mwamunaaligone – Galinsoga parviflora, Zumba – Crotalaria ochroleuca, Kamganja – Brassica juncea, Chikaka/Chipwete – prickly cucumber – Momordica foeda).
• Exotic Vegetables: (e.g., Cabbage, Rape, Lettuce, Carrot, Cucumber, Eggplant, Tomatoes, Beans and Peas, Onions, Cauliflower, Pepper, Beetroot).

3. Advantages of Indigenous Vegetables

Indigenous vegetables offer several benefits:

• Higher nutritional value than many exotic varieties.
• Better adaptation to local environmental conditions.
• Often grow naturally with less care compared to exotic types.

4. Site Selection for Vegetable Growing

A suitable site for vegetable growing requires:

• Adequate and permanent water supply.
• Well-drained and fertile soils, ideally sandy loam.
• Proximity to the market to reduce transport costs and ensure freshness.
• Sufficient land size to accommodate all planned vegetables.

5. Vegetable Garden Fence Construction

Steps to construct a fence:

1. Mark the field boundary.
2. Dig holes for poles.
3. Fix poles around the field.
4. Attach cross members to poles.
5. Thatch with grass/reeds, tying them to cross members.
6. Trim the grass.

Importance of Fencing:

• Protects vegetables from animals.
• Shields vegetables from strong winds.

6. Seedbed Preparation

Preparing a seedbed involves:

• Ploughing: To 25-30 cm depth for aeration and drainage.
• Harrowing: Breaking clods into fine particles for a fine tilth.
  • Importance of fine tilth: Allows correct seed planting depth and prevents large lumps from hindering germination.
• Applying manure: Enhances soil fertility, structure, color, and nutrient supply.
• Levelling the ground: Reduces run-off.
• Constructing across the slope: Raised beds are for rainy season (excess water drainage), sunken beds for dry season (water retention). Nursery beds are for raising seedlings before transplanting. Use 3-4-5 or triangulation method for right angles.

7. Sowing Vegetables

Vegetables are sown in two ways:

• Direct Sowing: Seeds are sown directly into the main field where they will grow to maturity. Suitable for vegetables sensitive to root disturbance (e.g., carrot, beetroot, spinach, turnips, okra, cucumbers, pumpkins, beans, peas, chitambe).
• Indirect Sowing (Nursery Beds): Seeds are sown in a nursery and later transplanted. Ideal for vegetables that tolerate root disturbance (e.g., cabbage, eggplant, rape, lettuce, luni, denje, chisoso).
  • Advantages of Nurseries: Easier seedling start, allows early start to growing season.
  • Steps for Indirect Sowing: Irrigate nursery, make drills, mix seeds with sand/sawdust and sow, cover with soil, mulch with vegetative materials (protects from sun), water.

8. Caring for Vegetable Seedlings

General care for seedlings involves:

• Mulch Removal: Gradually reduce and remove mulching grass after germination.
• Water Application: Apply water once or twice daily, adjusting for soil water loss. Avoid overwatering.
• Fertilizer Application: Nitrogen-rich fertilizers (e.g., CAN) and manure are beneficial for rapid growth.
• Weeding: Remove weeds to prevent competition for nutrients, air, sunlight, and water.
• Tilling: Loosen soil particles with a hand fork for better water and air circulation.
• Organic/Inorganic Fertilizers: Organic manure improves soil physical properties.
• Thinning: Uproot excess seedlings from seedbeds to prevent competition. Water before thinning.
• Hardening Off: Gradually reduce water to seedlings 2 weeks before transplanting to toughen them for new conditions.

9. Transplanting Vegetables

Steps for transplanting:

1. Thoroughly water both nursery and main field.
2. Mark planting stations with recommended spacing.
3. Lift seedlings from nursery with minimal root disturbance using a spade.
4. Insert transplants into holes and firm soil around them.
5. Mulch transplants with grass or banana leaves (conserves moisture, suppresses weeds, controls erosion/compaction, protects from sun).
6. Water the transplants.
7. Remove mulches once transplants are well established.

10. Caring for Transplants

• Fertilizer Application: Apply organic and inorganic fertilizers.
• Staking: Support vegetable stems (e.g., tomatoes) with sticks to keep fruits off the ground.
• Desuckering: Remove suckers for better quality vegetable development.

11. Controlling Pests and Diseases

Common Vegetable Diseases: Leaf spot, powdery mildew, root rot, damping-off.

• Leaf Spot Control: Spray Daconil, practice crop rotation, plant clean seeds, rogue infected plants.
• Damping-off Control: Regulate water application, ensure correct plant population.

Common Vegetable Pests:

• Piercing and Sucking Pests (e.g., aphids, thrips, mites): Pierce and suck sap, causing distortion. Control with Dimethoate or Rogor.
• Biting and Chewing Pests (e.g., nematodes, caterpillars, cutworms, locusts, mammals, birds): Cause physical damage.
  • Nematodes: Crop rotation, soil fumigation.
  • Caterpillars/Cutworms: Spray Carbaryl or Malathion.

Methods of Pest and Disease Control:

• Cultural Methods: Crop rotation, destroying crop residues, planting resistant varieties, rogueing, ploughing, early planting, using clean planting materials, correct spacing.
• Physical Methods: Flooding (suffocate soil pests), heat treatment (kill pathogens), hand picking.
• Biological Methods: Using one living organism to inhibit a pathogen.
• Chemical Methods: Using specific chemicals (fungicides, bactericides, nematicides, acaricides).
• Legislative Procedures: Laws to prevent introduction or spread of pests (routine inspection of exports, quarantine of imports).

12. Harvesting Vegetables

Factors Determining Harvesting Time:

• Intended use: Relish vs. seeds.
• Consumer taste/preference: Immature/tender vs. mature/hard.
• Market demand: Harvest earlier if demand is high.
• Pest and disease outbreak: May prompt earlier harvest to control issues.
• Prevailing weather conditions: Some crops prefer wet, others dry.

Methods of Harvesting:

• Leafy vegetables: Cut with a knife (slanting downwards) in the morning or late afternoon. Pack loosely.
• Fruit vegetables: Pluck gently without squeezing. Keep stalks if not fully ripe.
• Root vegetables and bulbs: Uproot gently (e.g., carrot, onion).
• Legumes: Pick pods from stem (peas, beans) or dig (ground beans).