Introduction
- Botanical Name: Juglans regia L.
- Family: Juglandaceae
- Common Name: Walnut
- Origin: Central Asia, Persia, and Himalayan regions.
- Major Producing Countries: China, USA, Iran, Turkey, India, Ukraine, and France.
- Indian Scenario: Mainly grown in Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Arunachal Pradesh, and Sikkim.
Morphology and Description
- Tree: Large, deciduous, long-living tree (25-30 m height), deep-rooted with a spreading canopy.
- Leaves: Pinnately compound with 5-9 leaflets.
- Flowers:
- Monoecious (male and female flowers separate but on the same tree).
- Male flowers in catkins, female flowers in terminal clusters.
- Fruit:
- A drupe with a hard shell containing an edible kernel.
- Green outer husk encloses the nut and dehisces at maturity.
Climate and Soil Requirements
Climate
- Requires temperate climate with cold winters and moderate summers.
- Needs chilling hours (800-1500 hours below 7°C) for proper bud break.
- Frost during flowering affects yield.
- Prefers an altitude of 900-3000 m in the Himalayan region.
Soil
- Deep, well-drained sandy loam or loamy soil with good fertility.
- pH range: 6.0-7.5 (slightly acidic to neutral).
- Avoid heavy clayey and waterlogged soils.
Propagation and Rootstocks
Propagation Methods
- Seed propagation: Used for rootstock development.
- Grafting and Budding: Used for commercial propagation.
- Patch budding (July-August)
- Cleft and whip grafting (late winter)
- Micropropagation: In-vitro propagation through tissue culture is gaining importance.
Common Rootstocks
- Juglans regia (Seedling rootstock)
- Juglans nigra (Black Walnut) – Resistant to soil-borne diseases
- Juglans hindsii (California Black Walnut) – Drought resistant
Planting and Orchard Management
Planting
- Spacing: 10 x 10 m for seedling trees, 6 x 6 m for grafted trees.
- Pit Size: 1m x 1m x 1m filled with FYM and topsoil.
- Best time for planting: Winter dormancy period (December-February).
Training and Pruning
- Training Systems:
- Central leader system preferred.
- Pruning:
- Light pruning in early years to maintain framework.
- Annual pruning of diseased and weak branches during dormancy.
Nutrient and Water Management
Fertilizer Application
- FYM (Farm Yard Manure): 20-25 kg/tree annually.
- Recommended NPK Dose (per tree/year):
- Nitrogen (N): 500-700 g
- Phosphorus (P2O5): 300-400 g
- Potassium (K2O): 800-1000 g
Irrigation Management
- Requires 6-8 irrigations per year in dry conditions.
- Critical irrigation stages: Bud swelling, flowering, nut development.
- Avoid overwatering to prevent root rot.
Pollination and Fruit Set
- Self-incompatible; requires cross-pollination.
- Wind-pollinated (Anemophilous).
- Planting 2-3 pollinizer varieties increases fruit set.
- Common Pollinizer Varieties:
- Chandler, Payne, Serr for commercial orchards.
Major Varieties of Walnut
Indian Varieties
- Local Seedling Types
- Gulab, Mehrab, Kagzi, Kashmiri Special
International Varieties
- Chandler (USA) – High yield, thin shell
- Franquette (France) – Late blooming, frost-resistant
- Hartley, Howard, Serr – Popular in commercial farming
Major Diseases and Pests
Diseases
- Walnut Blight (Xanthomonas campestris pv. juglandis) Symptoms: Dark spots on leaves and nuts. Control: Copper fungicides (Bordeaux mixture 1%).
- Root Rot (Phytophthora spp.) Control: Proper drainage, fungicide treatment.
- Anthracnose (Gnomonia leptostyla) Control: Mancozeb or Chlorothalonil sprays.
Pests
- Walnut Husk Fly (Rhagoletis completa) Control: Insecticide sprays (Malathion, Neem oil).
- Aphids and Mites Control: Neem-based bio-pesticides.
- Rodents (Squirrels, Rats) Control: Traps and fencing.
Harvesting and Yield
Harvesting
- Maturity Index: Green husk splits, kernel turns brown.
- Harvesting period: September-October.
- Methods: Handpicking, mechanical shaking.
Yield
- Seedling trees: 15-20 kg/tree (after 8-10 years).
- Grafted trees: 25-40 kg/tree (after 5-7 years).
Post-Harvest Management
Processing
- Hulling: Removal of green husk.
- Drying: Sun drying or artificial drying at 43-49°C.
- Storage: Low humidity, cool conditions (~5°C, 60% RH).
Storage Diseases
- Molds, Aflatoxins (due to improper drying).
- Control: Proper aeration, low temperature storage.
