Walnut | Subtropical and Temperate Fruit Production (HOR-MA201) - Unit 4 Notes - Chapter 15

Subtropical and Temperate Fruit Production

HORMA 201 - M.Sc. (Ag.) Horticulture

UNIT IV: Nuts- Walnut, Almond, Pistachio, Pecan

Table of Contents Commercial varieties of regional, national and international importance, Ecophysiological requirements, recent trends in propagation, rootstock influence, planting systems, cropping systems, root zone and canopy management, nutrient management, water management, fertigation, bioregulation, abiotic factors limiting fruit production, physiology of flowering, fruit set and development, abiotic factors limiting production, physiological disorders-causes and remedies, quality improvement by management practices; maturity indices, harvesting, grading, packing, precooling, storage, transportation and ripening techniques; industrial and export potential, Agri Export Zones(AEZ) and industrial support.

Chapter 15 -

🌰 WALNUT (Juglans regia L.)

Family: Juglandaceae
Chromosome Number: 2n = 32
Origin: Persia/Iran, spread to Central Asia and the Himalayas
Common names: English walnut, Persian walnut
India's leading walnut states: Jammu & Kashmir (90%+), Himachal Pradesh, Uttarakhand, Arunachal Pradesh

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🔹 1. Commercial Varieties of Regional, National & International Importance

India (Local cultivars):

• Sulaiman, Kagzi, Nooruk (Kashmir)
  
• Lake English: Thin-shelled
  
• Franquette, Chandler (Introduced varieties)

Internationally Popular Cultivars:

• Chandler: Most popular, high-yielding, lateral bearing
  
• Serr: Early bearing, good kernel
  
• Hartley: Medium-large nuts, well-sealed shell
  
• Pedro: Suitable for high-density planting
  
• Payne, Tehama, Franquette: USA
  
• Lara (France): Good quality, semi-lateral bearer

🔹 2. Ecophysiological Requirements

• Climate: Temperate, requires chilling hours: 400–1,500 hrs

• Temperature:

• Dormancy chilling: 0–7°C

• Growth: 15–30°C

• Sensitive to spring frost (flowers, shoots)

• Altitude: 1,200–2,500 m

• Soil: Deep, well-drained loam, pH 6–7.5; intolerant to waterlogging

🔹 3. Recent Trends in Propagation

• Seed propagation: Used for rootstock

• Vegetative propagation:

• Grafting: Side veneer, cleft, and patch budding

• Micropropagation: For elite clones

• In vitro grafting: Emerging trend

• Use of clonal rootstocks for uniformity

🔹 4. Rootstock Influence

• J. regia seedlings: Common in India

• J. nigra: More vigorous, disease-tolerant (Phytophthora)

• Clonal rootstocks: Improve yield, reduce juvenility

• Influence on precocity, tree size, and tolerance to soil and climatic stresses

🔹 5. Planting Systems

• Spacing:

• Traditional: 10 m × 10 m

• Semi-intensive: 7–8 m

• High-density: 5–6 m (with dwarf varieties like Pedro)

• System: Square, hedgerow in HDP

• Training: Modified central leader system

🔹 6. Cropping Systems

• Monocropping is preferred in commercial orchards

• Intercropping in young plantations: Pea, beans, pulses, or fodder crops

• Avoid crops that compete for nutrients/light

🔹 7. Root Zone and Canopy Management

• Shallow roots: Sensitive to root disturbance

• Canopy: Requires periodic thinning

• Pruning for light penetration, air circulation

• Lateral bearing varieties → more pruning attention

🔹 8. Nutrient Management

• FYM: 30–40 kg/tree/year

• NPK (for mature trees):

• N: 600–800 g/tree

• P₂O₅: 250–300 g

• K₂O: 300–400 g

• Micronutrients: Zn, B, Mn essential

• Boron: Improves nut set and quality

🔹 9. Water Management

• Irrigation critical during flowering and nut development

• Drip irrigation preferred

• Avoid water stagnation → root rot

• Mulching beneficial to conserve moisture

🔹 10. Fertigation

• Allows split NPK doses

• Reduces nutrient loss

• Enhances nut size and yield

• Suitable for high-density walnut orchards

🔹 11. Bioregulation

Bioregulator	Role
GA₃	Enhances shoot elongation
Paclobutrazol	Controls excessive vegetative growth
Ethrel	Helps in de-suckering
Boron & Zinc	Improves nut set, quality

🔹 12. Abiotic Factors Limiting Production

• Spring frost: Most damaging; affects catkins and shoots

• High humidity: Promotes blight and rot

• Water stress: Poor nut fill

• Chilling injury in low-altitude regions

🔹 13. Physiology of Flowering, Fruit Set & Development

• Monoecious: Male catkins and female flowers separate

• Dichogamy common (Protandry/Protogyny)

• Pollination: Wind

• Nut development: Takes 4–5 months post-pollination

🔹 14. Physiological Disorders – Causes & Remedies

Disorder	Cause	Remedy
Pistillate flower abscission	High temperature, hormonal imbalance	Anti-ethylene sprays (AVG)
Nut drop	Moisture stress	Timely irrigation
Empty nuts	Boron deficiency, poor pollination	Boron spray, synchronized flowering
Sunburn	High temp exposure	Whitewashing trunk, canopy management

🔹 15. Quality Improvement by Management Practices

• Use of lateral bearing, thin-shelled cultivars

• Proper pruning and canopy structure

• Balanced nutrition and irrigation

• Pest & disease management (blight, borers)

🔹 16. Maturity Indices

• Husk splits and turns brown

• Nut drops easily from husk

• Kernel turns light brown, fully filled

• Harvest before natural fall to reduce loss

🔹 17. Harvesting, Grading, Packing

• Harvest: Manual or mechanical shaking

• De-husking: Immediately after harvest

• Drying: To ~8% moisture content

• Grading: Based on size, shell thickness, kernel quality

• Packing: In jute bags or cartons; keep dry

🔹 18. Precooling, Storage & Transportation

• Precooling not necessary if dried

• Storage:

• Temp: 0–4°C

• RH: 55–65%

• Vacuum packing extends shelf life

• Protect from moulds and insect pests

• Transportation in moisture-proof containers

🔹 19. Ripening Techniques

• Walnuts ripen physiologically on tree

• No artificial ripening needed

• Post-harvest drying is key

🔹 20. Industrial & Export Potential

• Uses: Confectionery, bakery, cosmetics, oil, health foods

• By-products: Shells (activated carbon), hulls (dye)

• India exports kernels to:

• UK, France, UAE, Germany

• Potential for walnut oil, bakery-grade kernels

🔹 21. Agri Export Zones (AEZ) & Industrial Support

• J&K AEZ: For apple and walnut (old AEZ scheme)

• Support schemes:

• NHB, MIDH, APEDA

• Cold storage & processing units

• Challenges:

• Fragmented orchards

• Lack of post-harvest facilities

• Opportunities:

• Organic walnuts

• Value-added products (shelled, flavoured, oil)

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