Introduction
Walnut (Juglans regia L.) is a high‐value temperate nut crop prized for its nutritional richness, oil content, and various culinary and industrial uses. In India, it is mainly cultivated in Jammu & Kashmir, Himachal Pradesh, and Uttarakhand. With rising demand and export opportunities, walnut cultivation is gaining momentum in temperate regions of India.
Soil and Climate
Soil: Deep, well-drained loamy or sandy loam soils with pH 6.0–7.5 and good organic content are ideal. Heavy soils should be avoided.
Climate: Walnut requires 800–1500 chilling hours below 7°C for proper dormancy break. Spring frosts and hot summers should be avoided. Rainfall of 800–1200 mm is sufficient.
Variety
- Chandler: High yield, late leafing, good kernel quality.
- Vina: Early fruiting, good kernel recovery.
- Franquette: Cold-hardy, late flowering.
- Local selections: Traditional varieties from Kashmir and Himachal.
Propagation and Rootstock
Propagation: Through seedling rootstocks, whip grafting, or T-budding. Micropropagation is experimental.
Rootstocks: Juglans regia seedlings are commonly used. Hybrid rootstocks are being evaluated.
Planting Density, Planting Time, Planting Method
- Time: Winter planting (January–February); autumn planting (October–November) in mild climates.
- Spacing: 10 × 10 m (100 trees/ha) standard; 8 × 8 m or 8 × 6 m for high density.
- Method: 1×1×1 m pits filled with FYM and SSP. Place graft union 5 cm above soil level. Irrigate immediately.
Irrigation
- Young trees: Water every 7–10 days.
- Fruit-bearing trees: Irrigate every 10–14 days in spring, and every 7–10 days during summer.
- Method: Basin, furrow, or drip irrigation (recommended for water use efficiency).
Manure and Fertilizers
| Tree Age (Years) | FYM (kg/tree) | N (g) | P2O5 (g) | K2O (g) |
|---|---|---|---|---|
| 1–3 | 20–30 | 200 | 100 | 100 |
| 4–6 | 40–60 | 400 | 200 | 200 |
| 7–10 | 60–80 | 800 | 400 | 400 |
| >10 | 80–100 | 1000 | 500 | 500 |
Micronutrients: Apply zinc sulphate and boron sprays based on deficiency symptoms.
Intercultural Operation
Weeds should be controlled by mulching or herbicides. Legumes can be used as intercrops or green manures. Manual weeding is preferred around the tree basin.
Training and Pruning
Training: Modified central leader system is ideal for walnuts.
Pruning: Perform in winter to remove dead, diseased, or crossing branches. Light summer pruning enhances light penetration and air movement.
Major Pest
- Walnut aphid: Causes leaf curling and yellowing. Control with neem or Imidacloprid.
- Codling moth: Larvae bore into nuts. Use pheromone traps and insecticides.
- Husk fly: Larvae damage husk and kernel. Apply bait sprays and maintain orchard hygiene.
Major Disease
- Bacterial blight: Use copper sprays during bud break and after rain.
- Root rot: Caused by Phytophthora, prevented by proper drainage.
- Anthracnose: Preventive sprays with mancozeb during wet seasons.
Harvesting
Harvest Time: September to October, based on variety and altitude. Indicators include hull splitting and kernel fill.
Method: Hand-picking or mechanical shaking. Immediate dehulling and drying is necessary to prevent spoilage and staining.
Yield
Grafted trees start bearing from 4–5 years and reach full production by 10 years.
- 5–7 year trees: 1–2 tons/ha
- 10+ years: 3–5 tons/ha (standard), up to 7–8 tons/ha (high density)