Unit 4: Production Technology of Temperate and Nut Crops

I. Orientation: Principles of Temperate-Fruit Production

Temperate fruit crops enter winter dormancy and generally require a cultivar-specific exposure to cool temperatures before normal bud break. Successful production therefore depends on matching chilling requirement, frost risk, rootstock, pollination system and orchard management to the site.

• Defining characteristics:
  • Dormancy and chilling: Insufficient winter chilling causes delayed bud break, weak flowering and uneven fruit maturity; low-chill cultivars permit production in warmer regions.
  • Frost sensitivity: Swollen buds, flowers and young fruits are more vulnerable than dormant wood; low-lying frost pockets should be avoided.
  • Pollination: Apple, pear and almond commonly require compatible cross-pollinizers and insect activity, whereas peach and strawberry cultivars are often self-fruitful.
  • Rootstocks: Rootstocks control vigour, bearing age, anchorage and tolerance to soil pests, drought or waterlogging.
  • Canopy management: Training develops the framework; annual pruning regulates light, renewal growth, fruiting wood and crop load.
  • Orchard population: Under rectangular planting, tree number is calculated as:

N = 10,000 ÷ (R × P)

Here, N is plants per hectare, R is row spacing in metres and P is plant spacing within the row in metres.

• Harvest principle: Climacteric fruits such as apple, pear and peach may continue ripening after harvest; non-climacteric strawberry must be harvested near eating maturity.

II. Apple — Controlled Vigour and Balanced Cropping

A. Apple

Apple (Malus domestica, family Rosaceae) is a long-lived pome fruit whose productivity depends on chilling, compatible pollination and balanced vegetative growth.

• Climate and soil: Traditional cultivars commonly need about 800–1,600 chilling hours, while low-chill types require less; deep, fertile, well-drained loam with approximately pH 6.0–7.0 is preferred.
• Cultivars: ‘Red Delicious’, ‘Royal Delicious’, ‘Golden Delicious’, ‘Gala’, ‘Fuji’ and ‘Granny Smith’ differ in colour, maturity and chilling requirement.
• Fruit type: The edible portion is mainly the fleshy thalamus surrounding the papery core.

B. Propagation and Orchard Establishment

Apple is clonally propagated so that the scion cultivar and rootstock jointly determine tree performance.

• Propagation: Tongue grafting or budding is performed on seedling or clonal rootstocks.
• Rootstocks: M.9 produces dwarf, precocious trees requiring support; MM.106 is semi-vigorous; MM.111 is more vigorous and drought tolerant.
• Planting: Traditional orchards use wider spacing, while dwarf high-density systems may use approximately 3–4 m between rows and 1–2 m within rows.
• Pollinizers: Compatible cultivars with overlapping bloom should occupy about 25–33% of trees; honeybee colonies improve pollen transfer.

C. Training and Crop Regulation

Apple canopies must intercept light while supporting fruit-bearing spurs.

• Training: Central-leader, slender-spindle and tall-spindle systems suit progressively higher planting densities.
• Pruning: Remove crowded, diseased and competing branches, but retain productive spurs on two-year-old and older wood.
• Thinning: Hand or chemical thinning reduces biennial bearing; one fruit per cluster or about 10–15 cm between fruits improves size.
• Nutrition and water: Nitrogen is applied according to leaf analysis and vigour; drip irrigation is especially important during fruit enlargement.

D. Harvest and Protection

Harvest maturity determines storage life and market quality.

• Maturity indices: Ground-colour change, starch breakdown, seed browning, firmness and soluble solids are used together.
• Disorders and pests: Apple scab, powdery mildew, woolly apple aphid and codling moth require sanitation, monitoring and need-based control.
• Storage: Rapid precooling and controlled-atmosphere storage slow respiration and preserve firmness.

III. Pear — Pollination and Maturity Management

A. Pear

Pear includes European pear (Pyrus communis) and Asian pear (P. pyrifolia), both pome fruits adapted to cool winters.

• Climate: European pears generally need substantial chilling; Asian and low-chill cultivars extend production into milder areas.
• Cultivars: ‘Bartlett’, ‘Bosc’ and ‘Conference’ represent European types; ‘Patharnakh’, ‘Shinseiki’ and ‘Hosui’ represent Asian types.
• Soil: Deep, well-drained loams are ideal, although pear generally tolerates heavier soils better than apple.

B. Propagation and Pollination

Pear orchards require careful rootstock selection and compatible flowering combinations.

• Rootstocks: Pyrus seedlings produce vigorous trees; quince rootstocks induce dwarfing and early bearing.
• Compatibility: Some pear cultivars are incompatible with quince and require a compatible interstem between rootstock and scion.
• Pollination: Many cultivars are self-incompatible; two or more cultivars with overlapping bloom and viable pollen are planted together.
• Propagation: Shield budding, chip budding or grafting maintains cultivar identity.

C. Canopy and Crop Management

Pear trees must be managed to prevent excessive upright growth and limb breakage.

• Training: Modified central-leader or spindle systems produce strong branch distribution.
• Branch positioning: Spreading young limbs to angles near 45–60° reduces vigour and encourages flower-bud formation.
• Thinning: Fruit clusters are thinned to improve size and reduce alternate bearing.
• Health management: Fire blight, pear psylla, scab and fruit rots are managed through sanitation, balanced nitrogen and timely protection.

D. Harvest and Ripening

European and Asian pears require different harvest strategies.

1. European pears: Harvested mature but firm, then conditioned and ripened off the tree to avoid internal breakdown.
2. Asian pears: Harvested near tree-ripe stage because their crisp texture and flavour develop on the tree.

• Indices: Firmness, skin colour, soluble solids, seed colour and days from full bloom guide harvest.

IV. Peach — Renewal of One-Year-Old Fruiting Wood

A. Peach

Peach (Prunus persica, Rosaceae) is a stone fruit that bears mainly on shoots produced during the previous season.

• Climate: Cultivars range from low- to high-chill types; spring frost during bloom can destroy the crop.
• Cultivars: ‘Early Grande’, ‘Shan-e-Punjab’, ‘July Elberta’, ‘Redhaven’ and ‘Flordasun’ suit different chilling zones.
• Soil: Well-drained sandy loam is essential because peach roots are highly sensitive to waterlogging.

B. Propagation and Planting

Budded plants provide uniform trees and allow adaptation to soil constraints.

• Methods: T-budding or chip budding is commonly performed on peach seedling or selected clonal rootstocks.
• Rootstocks: Nemaguard offers resistance to some root-knot nematodes; peach–almond hybrids provide vigour and drought tolerance.
• Spacing: Conventional orchards commonly use approximately 5–6 m spacing, adjusted for rootstock and machinery.
• Pollination: Most commercial cultivars are self-fruitful, although bee activity improves fruit set.

C. Training, Pruning and Thinning

Annual renewal pruning is indispensable because old shoots do not repeatedly produce equivalent crops.

• Training: Open-centre or vase training creates three to four main scaffolds and exposes fruiting shoots to sunlight.
• Pruning: Remove weak, shaded and excessively upright shoots while retaining well-spaced one-year-old shoots.
• Thinning: Fruits are usually spaced about 15–20 cm apart after natural fruit drop.
• Irrigation: Moisture stress during pit hardening and final swell reduces fruit size; excessive late nitrogen delays maturity.

D. Harvest and Protection

Peach fruit bruises easily and must be harvested according to intended market distance.

• Maturity: Ground colour, firmness, aroma and soluble solids are more reliable than red blush.
• Pests and diseases: Peach leaf curl, brown rot, bacterial canker, fruit fly and stem borers require clean orchards and timely treatment.
• Handling: Fruits are picked with minimal pressure, precooled quickly and packed in shallow containers.

V. Strawberry — Intensive Production of a Non-Climacteric Berry

A. Strawberry

Cultivated strawberry (Fragaria × ananassa, Rosaceae) is a perennial herb commonly managed as a short-duration annual crop.

• Plant structure: The crown produces leaves, roots, flowers and horizontal runners; the edible portion is an enlarged receptacle bearing achenes.
• Types: Short-day cultivars initiate flowers under short days and cool temperatures; day-neutral types flower across a wider photoperiod.
• Cultivars: ‘Chandler’, ‘Sweet Charlie’, ‘Camarosa’, ‘Festival’ and ‘Winter Dawn’ are widely grown under suitable regional conditions.

B. Planting Material and Establishment

Healthy runner plants and correct crown placement determine stand uniformity.

• Propagation: Runner plants are raised in disease-free nurseries; tissue culture supplies pathogen-tested mother stock.
• Beds: Raised beds improve drainage and root aeration; black plastic mulch suppresses weeds and keeps fruits clean.
• Planting: The crown is kept at soil level because deep planting causes crown rot and shallow planting exposes roots.
• Spacing: Approximately 30 × 30 cm is common, with adjustment for cultivar and bed system.

C. Nutrition, Irrigation and Crop Care

Strawberry’s shallow root system requires frequent, controlled inputs.

• Water: Drip irrigation maintains moisture without prolonged leaf and fruit wetness.
• Fertigation: Split nitrogen and potassium applications support canopy growth, flowering and fruit filling without excessive softness.
• Flower management: Early flowers may be removed from weak transplants to promote crown establishment.
• Pollination: Bees improve achene fertilization; poor pollination produces misshapen berries.

D. Harvest and Protection

Strawberry must be harvested close to consumption maturity because it does not sweeten substantially after picking.

• Harvest: Berries are picked with calyx and a short stalk at the colour stage required by market distance.
• Temperature: Rapid precooling near 0°C greatly slows deterioration.
• Constraints: Grey mould, anthracnose, powdery mildew, mites and fruit rot are reduced through clean plants, ventilation, sanitation and dry fruit surfaces.

VI. Almond — Frost-Sensitive Nut of Dry Climates

A. Almond

Almond (Prunus dulcis, Rosaceae) is a deciduous stone fruit cultivated for its edible kernel.

• Climate: Cool winters, dry summers and low humidity favour production; very early flowering makes crops vulnerable to spring frost.
• Soil: Deep, well-drained loams are preferred; standing water promotes root and crown diseases.
• Cultivars: ‘Nonpareil’, ‘Ne Plus Ultra’, ‘Carmel’ and self-fertile ‘Independence’ differ in shell hardness and pollination behaviour.
• Kernel safety: Commercial sweet almonds differ from bitter types containing high levels of cyanogenic compounds.

B. Propagation and Orchard Design

Almond orchards combine vegetatively propagated cultivars with adapted root systems.

• Propagation: T-budding is commonly used on almond, peach or peach–almond hybrid rootstocks.
• Rootstocks: Peach performs well in lighter irrigated soils; almond provides drought adaptation; hybrids provide vigour.
• Pollination: Most traditional cultivars are self-incompatible, requiring interplanted compatible cultivars and honeybees during bloom.
• Spacing: Approximately 6–7 m is used in conventional orchards, depending on vigour.

C. Canopy and Crop Management

A strong, illuminated canopy supports regular nut production.

• Training: Open-centre or modified-leader systems develop three to four well-spaced scaffolds.
• Pruning: Young trees require structural pruning; mature trees need removal of dead, crossing and shaded wood.
• Water: Irrigation is critical during kernel filling, although controlled postharvest deficits may conserve water.
• Protection: Blossom blight, shot-hole disease, aphids and navel orangeworm are managed through sanitation and monitoring.

D. Harvest and Processing

Almond maturity is identified by hull splitting and drying of the shell.

• Harvest: Trees are shaken when most hulls split; nuts are collected promptly to limit contamination and insect damage.
• Processing: Hulling and shelling are followed by drying kernels to a safe moisture level, commonly near 5–7%.
• Storage: Cool, dry, odour-free conditions delay rancidity in the oil-rich kernels.

VII. Walnut — Large-Canopy Nut with Dichogamous Flowering

A. Walnut

Persian or English walnut (Juglans regia, Juglandaceae) is grown for edible kernels and valuable timber.

• Climate: It requires winter chilling and a sufficiently long growing season; spring frost injures emerging shoots and pistillate flowers.
• Soil: Deep, fertile, well-drained soil is required because roots may extend beyond 2 m.
• Cultivars: ‘Chandler’, ‘Hartley’, ‘Franquette’ and ‘Serr’ differ in bearing habit, leafing date and nut quality.
• Bearing habit: Lateral-bearing cultivars produce flowers along one-year-old shoots and generally crop earlier than terminal bearers.

B. Propagation and Pollination

Vegetative propagation is necessary because walnut seedlings vary greatly and take longer to bear.

• Methods: Patch budding, flute budding and grafting are used, often under controlled temperature because callusing is difficult.
• Rootstocks: Seedlings of J. regia or adapted Juglans species provide vigour and anchorage.
• Flowering: Walnut is monoecious, bearing separate male catkins and female flowers on the same tree.
• Dichogamy: Male and female bloom may not overlap; suitable pollinizers are therefore distributed through the orchard.

C. Training and Orchard Management

Walnut needs a strong framework capable of supporting a large canopy and heavy crops.

• Training: Central-leader or modified central-leader systems produce a straight trunk with well-spaced scaffolds.
• Pruning: Young trees receive structural pruning; heavy mature-tree pruning is avoided because it stimulates excessive shoots.
• Irrigation: Adequate water during shell expansion and kernel filling prevents small nuts and dark, shrivelled kernels.
• Protection: Walnut blight, anthracnose, codling moth and husk fly are managed through sanitation, monitoring and timely control.

D. Harvest and Postharvest Handling

Walnuts are ready when kernels mature and green hulls begin separating from the shell.

• Harvest: Mechanical shaking or careful beating dislodges nuts; delayed collection causes dark kernels and mould.
• Processing: Nuts are hulled, washed and dried promptly to approximately 8% moisture.
• Quality: Large, well-filled nuts with light-coloured kernels command premium prices; cool, low-oxygen storage limits rancidity and insect damage.