Unit 4: Production Technology of Temperate and Nut Crops - Subjective Questions

Climatic requirements

• Apple is a temperate fruit crop that performs best under cool winters and mild summers.
• Most commercial cultivars require approximately 800–1,500 chilling hours below about for proper bud break and flowering. Low-chill cultivars require fewer chilling hours.
• A cool and relatively dry climate during flowering promotes effective pollination and fruit set.
• High temperature during fruit development may reduce colour development and fruit quality.
• Frost at flowering can damage blossoms and greatly reduce yield; therefore, frost-prone depressions should be avoided.
• Hail, strong winds and prolonged rainfall can injure fruits and increase disease incidence.

Soil requirements

• Deep, fertile and well-drained loam to sandy-loam soils are ideal.
• The soil should have good moisture-holding capacity and adequate organic matter.
• A soil depth of about 1–2 m is desirable for unrestricted root development.
• The optimum soil pH is generally around 5.5–6.5, although apple can tolerate a slightly wider range depending on the rootstock.
• Waterlogged, highly saline and strongly calcareous soils should be avoided.

Site selection

• Gentle slopes with good air drainage reduce frost injury.
• The orchard should receive adequate sunlight and have access to irrigation water.
• Rootstocks must be selected according to soil conditions, climate and the desired planting density.

Apple rootstocks influence tree vigour, precocity, yield efficiency, anchorage, planting density and tolerance to soil-related stresses.

1. Seedling rootstocks

• Produced from seeds, commonly from crab apple or vigorous apple types.
• Trees are vigorous, large and generally slow to come into bearing.
• They have a deep and extensive root system with good anchorage.
• Suitable for low-density orchards, rainfed situations and marginal soils.
• Trees show greater variability because seedlings are genetically non-uniform.

2. Semi-dwarfing rootstocks

• Examples include MM.106 and MM.111, subject to local suitability.
• Produce medium-sized trees and allow moderately high planting density.
• Trees bear earlier than those on seedling rootstocks.
• MM.106 performs well in many soils but is susceptible to collar rot in poorly drained sites.
• MM.111 is relatively vigorous and is often preferred where drought tolerance and anchorage are important.

3. Dwarfing rootstocks

• Examples include M.9 and M.26.
• Induce small tree size, early bearing and high yield efficiency.
• Suitable for high-density orchards and intensive canopy management.
• Usually require permanent support, regular irrigation and careful nutrient management.
• M.9 is susceptible to drought and poor anchorage, while M.26 may be prone to collar rot in unsuitable soils.

Thus, rootstock selection should be based on soil, climate, water availability, cultivar vigour, disease risk and orchard system.

Orchard planning

• Select dwarfing or semi-dwarfing rootstocks and compatible spur-type or moderate-vigour cultivars.
• Conduct soil testing, improve drainage and incorporate well-decomposed organic manure before planting.
• Plant healthy, certified and disease-free nursery trees.
• Spacing depends on rootstock and training system; dwarf trees are planted much closer than vigorous trees.
• Install a trellis or stake-support system before or immediately after planting.

Planting

• Plant during dormancy when the soil is workable.
• Keep the graft union about 15–20 cm above the soil surface so that the scion does not form roots.
• Irrigate immediately after planting and maintain a weed-free tree basin.

Training systems

• Slender spindle: A central leader with short, well-spaced fruiting branches.
• Tall spindle: Uses highly feathered trees, minimal heading and early branch bending.
• Vertical axis: Maintains a dominant central leader with tiers of fruiting branches.

Pruning and canopy management

• Remove competing leaders, diseased shoots and overly vigorous upright branches.
• Bend branches to wider angles to reduce vigour and encourage flower-bud formation.
• Maintain a narrow canopy so that light reaches the lower fruiting wood.
• Use renewal pruning to replace old, weak fruiting branches.
• Avoid severe dormant pruning because it stimulates excessive vegetative growth.

Other practices

• Provide drip irrigation and nutrients according to soil and leaf analysis.
• Retain suitable pollinizer cultivars and bee colonies.
• Thin fruits to maintain fruit size and regular bearing.

Yield efficiency may be assessed as:

Pollination

• Most apple cultivars are self-incompatible and require cross-pollination.
• Two or more compatible cultivars with overlapping flowering periods should be planted.
• Pollinizers may be distributed as complete rows, individual trees or grafted branches.
• Honey-bee colonies should be introduced at about 5–10% bloom, depending on orchard conditions.
• Excess insecticide use during flowering must be avoided to protect pollinators.

Fruit thinning

• Heavy fruit set results in small fruits, limb breakage and biennial bearing.
• Thinning may be done manually or with locally recommended chemical thinners.
• Hand thinning is generally completed after natural fruit drop, retaining one healthy fruit per cluster and appropriate spacing between fruits.
• Timely thinning improves fruit size, colour, quality and return bloom.

Important physiological disorders

• Bitter pit: Appears as sunken brown spots, mainly due to calcium imbalance. It is managed through balanced nutrition, calcium sprays, proper irrigation and avoidance of excessive nitrogen.
• Sunburn: Causes bleached or brown patches on exposed fruits. Maintain adequate foliage, irrigation and use approved sun-protection measures.
• Water core: Produces water-soaked, glassy flesh around vascular bundles. Avoid excessive maturity and harvest susceptible cultivars at the proper stage.
• Pre-harvest fruit drop: Reduced by balanced nutrition, timely irrigation, harvesting at correct maturity and approved growth-regulator treatments where recommended.
• Scald during storage: Managed through proper maturity at harvest, rapid cooling and suitable controlled storage practices.

Propagation

• Commercial pear cultivars are propagated vegetatively to maintain varietal identity.
• Tongue grafting, whip grafting, shield budding and T-budding are commonly used.
• Budding is usually performed when the bark slips easily, while grafting is done during the dormant season.

Rootstocks

• Pear seedlings: Produce vigorous, long-lived trees with good anchorage but delayed bearing.
• Quince rootstocks: Induce dwarfing and early bearing and are suitable for high-density planting.
• Some pear cultivars are incompatible with quince and require an interstock of a compatible cultivar.
• Rootstock selection depends on soil pH, drainage, climate, desired tree size and disease risk.

Orchard establishment

• Select deep, fertile, well-drained loam soil.
• Prepare the site through deep ploughing, drainage improvement and incorporation of organic matter.
• Lay out the orchard using the square, rectangular or contour system according to topography.
• Plant dormant nursery trees in prepared pits without burying the graft union.
• Irrigate immediately after planting and provide stakes where necessary.
• Include compatible pollinizer cultivars with overlapping bloom periods.

Initial care

• Head back the planted tree according to the chosen training system.
• Remove rootstock suckers and competing shoots.
• Maintain a weed-free basin and protect young trunks from rodents and sun injury.

Training

• Pear trees are commonly trained to a central leader or modified central leader system because of their naturally upright growth.
• In high-density orchards, spindle or vertical-axis systems may be adopted on dwarfing rootstocks.
• Scaffold branches should be well spaced vertically and distributed around the trunk.
• Branches may be spread or tied to develop wider crotch angles and encourage early fruiting.

Pruning

• Pear bears mainly on spurs located on two-year-old and older wood.
• Pruning should preserve productive spurs while removing dead, diseased, crossing and crowded branches.
• Water sprouts and root suckers should be removed regularly.
• Excessive heading should be avoided because it promotes upright vegetative growth and delays bearing.
• Old, weak and shaded fruiting wood should be renewed gradually.

Crop regulation

• Many cultivars require cross-pollination, so compatible pollinizers and bees are essential.
• Excessive fruit set should be reduced by hand or approved chemical thinning.
• Thinning improves fruit size, reduces limb breakage and promotes return bloom.
• Balanced nitrogen, irrigation and pruning help maintain an appropriate vegetative-to-reproductive balance.
• Fruits should be distributed uniformly throughout the canopy rather than concentrated at branch ends.

European pears are generally harvested at physiological maturity but before they become fully soft on the tree, whereas many Asian pears are harvested closer to eating maturity.

Maturity indices

• Number of days from full bloom
• Change in skin colour from dark green to lighter green
• Fruit size and firmness
• Soluble solids content
• Starch degradation and seed colour
• Ease of fruit separation from the spur

Harvesting

• Lift and twist the fruit gently to detach it without breaking the spur.
• Harvest in more than one picking when fruit maturity is uneven.
• Avoid bruising, puncturing and dropping fruits.
• Use padded field containers and keep harvested fruits in shade.

Ripening

• European pears require a period of cold conditioning in many cases, followed by ripening at moderate temperature.
• Controlled ethylene exposure may be used commercially for uniform ripening where recommended.
• Asian pears are usually marketed as crisp fruits and do not require softening like European pears.

Post-harvest handling

• Grade fruits according to size, colour, shape and freedom from defects.
• Remove diseased and damaged fruits.
• Pre-cool promptly to remove field heat.
• Store at low temperature and high relative humidity appropriate to the cultivar.
• Controlled-atmosphere storage can extend storage life by slowing respiration and ripening.
• Careful packaging prevents compression injury and abrasion.

Climate

• Peach requires a temperate to subtropical climate with a cultivar-specific winter chilling requirement.
• Cultivars range from low-chill types for mild winters to high-chill types for cooler regions.
• Warm, dry weather during fruit development improves quality, while rainfall near harvest may cause cracking and disease.
• Spring frost is highly damaging because peach flowers early.
• The site should have good air drainage and protection from strong winds.

Soil

• Deep, fertile and well-drained sandy-loam to loam soils are preferred.
• Peach is highly sensitive to waterlogging and poor soil aeration.
• A slightly acidic to neutral soil reaction is generally suitable.

Propagation

• Commercial cultivars are commonly propagated by T-budding or shield budding on seedling or clonal rootstocks.
• Rootstocks are selected for vigour, nematode resistance, soil adaptation, drought tolerance and compatibility.
• Healthy and true-to-type nursery plants should be used.

Planting

• Plant dormant trees during winter before active growth begins.
• Keep the bud union above the soil level.
• Irrigate immediately and head the tree back to initiate scaffold development.
• Spacing is adjusted according to rootstock, cultivar vigour, soil fertility and training system.
• Orchards should include irrigation, drainage and wind protection where required.

The open-centre or vase system is commonly preferred because peach requires abundant light and bears primarily on one-year-old shoots.

Advantages

• Allows sunlight to enter the centre of the canopy.
• Improves fruit colour, size and flower-bud development.
• Facilitates spraying, thinning and harvesting.
• Maintains a low, spreading and manageable tree.

Development of the system

1. Head the newly planted tree at approximately 60–75 cm, depending on local practice.
2. Select three or four strong shoots as primary scaffolds.
3. Scaffolds should be distributed around the trunk and separated vertically.
4. Remove the central leader to maintain an open centre.
5. Select outward-growing secondary branches on each scaffold during subsequent years.
6. Remove shoots growing toward the centre and branches with narrow crotch angles.

Annual pruning

• Remove dead, diseased, broken and crossing branches.
• Thin out old fruiting shoots because peach fruits on the previous season's growth.
• Retain an adequate number of healthy, moderately vigorous annual shoots.
• Head back excessively long shoots where needed to maintain canopy shape.
• Remove vigorous upright water sprouts from the centre.
• Avoid both under-pruning, which causes crowding and small fruits, and severe over-pruning, which stimulates excessive vegetative growth.

Pruning intensity should be adjusted according to tree vigour, expected crop load and cultivar growth habit.

Fruit thinning

• Peach often sets more fruits than the tree can develop to marketable size.
• Excess crop load results in small fruits, delayed maturity, poor colour, branch breakage and weak return bloom.
• Thinning is usually performed after the danger of major natural fruit drop has passed.
• Damaged, malformed, diseased and closely spaced fruits are removed first.
• Retain fruits at an appropriate spacing along the shoot, commonly about 10–15 cm, depending on cultivar, fruit size and shoot strength.
• Early and uniform thinning generally produces the greatest improvement in fruit size.

Water management

• Critical periods include flowering, fruit set, rapid fruit enlargement and post-harvest bud development.
• Drip irrigation is preferred because it supplies water efficiently and permits fertigation.
• Both drought stress and waterlogging should be avoided.
• Mulching helps conserve moisture and suppress weeds.

Nutrient management

• Apply nutrients according to soil testing, leaf analysis, tree age and expected yield.
• Nitrogen supports shoot and leaf growth but excess nitrogen reduces colour and increases soft growth.
• Potassium contributes to fruit size and quality.
• Calcium and micronutrients should be supplied only where deficiency or local recommendations justify application.
• Split fertilizer applications or fertigation improve nutrient-use efficiency.
• Organic manure and orchard-floor management help maintain soil structure and biological activity.

Botanical features

• Strawberry is a low-growing, herbaceous perennial generally cultivated as an annual or short-duration perennial crop.
• The compressed stem is known as the crown.
• Leaves are usually trifoliate and arise from the crown.
• The crop produces creeping stems called runners or stolons, which form daughter plants at nodes.
• The edible portion is an enlarged receptacle, while the true fruits are the small achenes present on its surface.

Climatic requirements

• Cool weather favours plant establishment, flowering and fruit development.
• Temperature and day length influence runner production, flower initiation and fruiting.
• High temperature may reduce fruit firmness and colour, while frost can damage flowers.
• Dry weather during fruit ripening reduces fruit rot.

Soil requirements

• Well-drained sandy-loam to loam soil rich in organic matter is preferred.
• Slightly acidic soil, generally around pH 5.5–6.5, is suitable.
• Saline, alkaline and waterlogged soils should be avoided.

Propagation

• Commercial strawberry is propagated mainly through runner plants.
• Healthy, well-rooted daughter plants are separated from selected mother plants.
• Tissue-cultured plants may be used to produce pathogen-free nuclear planting material.
• Mother blocks should be isolated, inspected and kept free from viruses, nematodes and fungal diseases.

Land and bed preparation

• Select a fertile, well-drained field and test the soil before planting.
• Incorporate well-decomposed organic matter and recommended basal fertilizers.
• Prepare raised beds to improve drainage, root-zone aeration and field operations.
• Install drip laterals before laying mulch.

Planting

• Use healthy, uniform and disease-free runner plants or plug plants.
• Plant at spacing suited to cultivar, bed width and number of rows.
• Keep the midpoint of the crown at soil level; deep planting causes crown rot, while shallow planting exposes roots.
• Irrigate immediately after transplanting.

Plastic mulch

• Black or locally recommended plastic mulch suppresses weeds, conserves moisture and prevents direct contact between fruits and soil.
• It also reduces splashing of soil-borne pathogens and keeps fruits cleaner.
• Mulch holes should fit closely around plants without covering the crown.

Drip irrigation and fertigation

• Apply frequent, light irrigation because strawberry has a shallow root system.
• Avoid prolonged wetting of foliage and fruits.
• Apply soluble nutrients in split doses through fertigation according to crop stage and soil analysis.
• Avoid excessive nitrogen, which promotes soft growth and fruit rot.

Additional management

• Remove unwanted runners so that assimilates are directed toward fruit production.
• Introduce bees or protect natural pollinators during flowering.
• Use row covers or frost-protection measures where necessary.
• Harvest ripe berries frequently and maintain strict field sanitation.

Harvesting

• Strawberry is non-climacteric and should be harvested at the colour stage required by the market.
• Fruits for distant markets are picked when partially coloured, while those for local sale can be harvested at a more advanced red stage.
• Harvest during the cool part of the day after surface moisture has dried.
• Pick fruits with the calyx and a short stalk without squeezing them.
• Frequent picking is necessary because ripe fruits deteriorate rapidly.

Grading and packaging

• Grade according to size, colour, shape, firmness and freedom from defects.
• Remove overripe, bruised, diseased and malformed berries.
• Pack directly into shallow, ventilated consumer containers to minimize handling.

Post-harvest management

• Move fruits to shade immediately and pre-cool rapidly.
• Maintain a low-temperature cold chain with high relative humidity.
• Avoid condensation and rough transport because berries are highly susceptible to decay and mechanical injury.

Integrated disease management

• Use certified disease-free plants and resistant cultivars where available.
• Plant on raised beds and maintain good drainage.
• Use drip irrigation instead of overhead irrigation.
• Remove infected leaves, flowers and fruits from the field.
• Rotate with non-host crops and avoid repeatedly planting strawberry in infested soil.
• Manage grey mould and other diseases through canopy aeration, sanitation, biological measures and need-based application of registered fungicides.
• Rotate fungicides with different modes of action to delay resistance.

Climate

• Almond grows best in regions with cool winters and warm, dry summers.
• A cultivar-specific amount of winter chilling is necessary for uniform bud break and flowering.
• Almond blooms very early; therefore, spring frost is a major production hazard.
• Dry weather during flowering favours bee activity, while rain and low temperature reduce pollination.
• Warm, dry conditions during nut maturation and harvest improve hull splitting and reduce fungal infection.

Soil

• Deep, fertile and well-drained loam soils are most suitable.
• Almond tolerates some drought because of its extensive root system but performs poorly under waterlogging.
• Salinity and excess boron may reduce growth and yield depending on rootstock and soil conditions.
• Soil depth, drainage and rootstock adaptation should be evaluated before planting.

Pollination

• Most traditional almond cultivars are self-incompatible and require compatible pollinizers.
• Cultivars must have overlapping flowering periods and cross-compatible pollen.
• Pollinizer trees should be distributed uniformly throughout the orchard.
• Honey-bee colonies are introduced at flowering to ensure pollen transfer.
• Insecticides harmful to bees must not be applied during bloom.
• Self-compatible cultivars reduce dependence on cross-pollinizers, but bee activity may still improve fruit set and yield.

Propagation

• Almond cultivars are propagated mainly by budding or grafting on suitable rootstocks.
• T-budding and shield budding are commonly adopted when the rootstock bark separates easily.
• Nursery plants should be healthy, true to type and free from crown gall and viruses.

Rootstock selection

• Almond seedlings: Vigorous and relatively drought tolerant; suited to deep, well-drained soils.
• Peach seedlings: Promote early growth but may be less suitable for dry or calcareous soils.
• Peach–almond hybrids: Vigorous and useful in some calcareous or drought-prone situations.
• Plum-related rootstocks: May be selected for heavier or imperfectly drained soils, depending on compatibility.
• Rootstocks are chosen according to soil texture, lime, salinity, nematodes, water availability and desired vigour.

Training

• Young trees are commonly trained to an open-centre or modified central leader system.
• Select well-spaced scaffold branches with strong crotch angles.
• Remove competing leaders and low, weak shoots.

Pruning

• Young trees require formative pruning to develop a strong framework.
• Bearing trees need relatively light pruning because excessive pruning stimulates vegetative growth.
• Remove dead, diseased, crossing and shaded branches.
• Renew unproductive fruiting wood gradually while preserving healthy spurs.
• Pruning cuts should be clean, and infected wood should be removed from the orchard.

Maturity indices

• The hull changes colour and begins to split along the suture.
• The shell becomes firm, and the kernel reaches full size with reduced moisture.
• Harvesting starts when most nuts show adequate hull split but before excessive nut drop or pest damage occurs.

Harvesting

• Nuts may be removed by manual beating with padded poles, branch shaking or mechanical trunk shaking.
• A clean orchard floor or catching sheet facilitates collection.
• Harvested nuts should not remain on damp soil because they may absorb moisture and become infected.

Hulling and shelling

• The fleshy hull is removed soon after harvest using manual or mechanical hullers.
• Nuts may be marketed in-shell or shelled depending on market demand.
• Damaged, mouldy and insect-infested nuts are discarded.

Drying

• Nuts are spread in thin layers and dried uniformly under hygienic conditions.
• Drying is continued until kernel moisture reaches a safe storage level, usually around 5–7%, subject to market standards.
• Overheating should be avoided because it can damage flavour and oil quality.

Storage

• Store nuts in clean, dry and insect-proof containers.
• Low temperature and low relative humidity reduce rancidity, mould growth and insect infestation.
• Prevent contamination by soil, chemicals, rodents and aflatoxin-producing fungi.
• Proper grading is based on kernel size, colour, damage, doubles and freedom from foreign matter.

Propagation

• Seed propagation is used primarily for raising rootstocks because seedlings do not remain true to the parent cultivar.
• Elite walnut cultivars are propagated by patch budding, ring budding, whip-and-tongue grafting or bench grafting.

Reasons for grafting difficulty

• Walnut tissues contain abundant sap and phenolic compounds that can interfere with callus formation.
• Graft success is strongly affected by temperature, humidity, scion condition and cambial alignment.
• Excessive sap flow or bleeding may prevent proper union formation.
• Callusing is most successful under a controlled warm temperature and adequate humidity.

Measures to improve success

• Use healthy, mature scion wood collected during dormancy.
• Store scions under cool and moist conditions without allowing desiccation.
• Match scion and rootstock diameters and align cambial layers accurately.
• Tie and seal the union to prevent moisture loss.
• Use hot-callusing or protected structures where appropriate.
• Remove rootstock sprouts below the graft union.

Orchard establishment

• Select a deep, fertile, well-drained site because walnut develops a large root system.
• Avoid frost pockets, shallow soils and waterlogged locations.
• Plant grafted trees during dormancy at a spacing suited to cultivar vigour and mechanization.
• Include suitable pollinizers where the main cultivar's pollen-shedding and pistillate-flower periods do not overlap.
• Provide irrigation, trunk protection and early training after planting.

Flowering behaviour

• Walnut is monoecious, producing separate male and female flowers on the same tree.
• Male flowers occur in catkins, while female flowers are borne singly or in small clusters.
• Pollination is mainly by wind.

Dichogamy

• The timing of pollen shedding and female receptivity often differs within a cultivar.
• Protandrous cultivars shed pollen before female flowers become receptive.
• Protogynous cultivars have receptive female flowers before pollen shedding.
• This condition reduces self-pollination and makes cultivar arrangement important.

Pollination management

• Select pollinizer cultivars whose pollen-shedding period overlaps the receptive period of the main cultivar.
• Pollinizers should be distributed so that wind can carry pollen throughout the orchard.
• Excessive distance between compatible trees can reduce fruit set.
• Weather during flowering affects pollen release, movement and stigma receptivity.

Bearing habit

• Terminal-bearing cultivars produce most female flowers at terminal buds and are generally less precocious.
• Lateral-bearing cultivars also bear female flowers on lateral buds of one-year-old shoots.
• Lateral-bearing cultivars usually come into production earlier and may yield more heavily.
• Pruning must preserve productive one-year-old shoots while maintaining canopy light and branch renewal.

Training and pruning

• Walnut trees are commonly trained to a modified central leader system.
• Develop a straight trunk and several strong, widely spaced scaffold branches.
• Young trees require formative pruning, while mature trees need moderate thinning and removal of dead or diseased wood.
• Excessive pruning should be avoided because large cuts heal slowly and may invite infection.
• Prune at a locally suitable time to reduce excessive sap bleeding.

Irrigation and nutrition

• Maintain adequate soil moisture during shoot growth, nut set and kernel filling.
• Avoid both water stress and waterlogging.
• Use drip or other efficient irrigation systems where possible.
• Apply fertilizers according to soil and leaf analysis; nitrogen and potassium are particularly important for growth and nut filling.
• Mulching and cover-crop management help conserve soil and improve orchard-floor conditions.

Harvesting

• Harvest when the green hull splits or separates readily and kernels are physiologically mature.
• Nuts are collected after natural fall or removed by shaking.
• Delayed harvesting may cause dark kernels, mould and insect damage.

Post-harvest management

• Remove hulls promptly and wash nuts where appropriate.
• Dry nuts rapidly and uniformly to a safe moisture content.
• Grade according to shell integrity, size, kernel colour, kernel recovery and freedom from defects.
• Store in cool, dry conditions to prevent rancidity, mould and insect infestation.
• Kernels intended for prolonged storage benefit from refrigeration and moisture-proof packaging.

Common principles

• Both crops require well-drained soil, suitable rootstocks and balanced irrigation.
• Prompt hulling and drying are essential for maintaining kernel quality.
• Clean harvesting and safe storage moisture reduce fungal contamination.
• Cultivar and pollinizer selection must be based on local climatic conditions and flowering behaviour.