Unit 4: Orchard establishment and management

1. Principles of Orchard Establishment

Orchard establishment is a long-term investment requiring meticulous planning. Mistakes made during establishment are often irreversible or costly to rectify later.

A. Site Selection and Analysis

Before planting, the following factors must be evaluated:

• Climate: Temperature range, chill hour requirements (for temperate fruits), rainfall distribution, and wind velocity must match the specific fruit crop.
• Soil: Deep, well-drained, loamy soils are generally preferred. A soil depth of 2m is ideal for large trees. Check for hard pans, water table depth (should be <2m), and pH levels.
• Topography: Avoid frost pockets (low-lying areas). On slopes, aspect (direction the slope faces) affects sunlight and temperature.
• Water Supply: Availability of perennial water sources for irrigation is critical, especially during establishment.

B. Preliminary Operations

• Clearing and Leveling: Removal of wild vegetation, stumps, and large stones.
• Fencing: Essential to protect young saplings from grazing animals and theft. Biological fencing (thorny hedges) or mechanical fencing (barbed wire) may be used.
• Windbreaks: Planting tall, fast-growing trees (e.g., Eucalyptus, Poplar, Casuarina) on the windward side (usually North-West) to protect fruit trees from desiccation, limb breakage, and flower drop.
  • Establishment: Planted 2–3 years prior to the orchard.

C. Layout Plan

The layout determines the number of trees per hectare and the ease of future farm operations (mechanization, spraying, harvesting).

2. Planting Systems and Planting Densities

A. Planting Systems

The geometric arrangement of trees in an orchard.

1. Square System:
   • The most common system. Trees are planted at corners of a square.
   • Pros: Easy to layout; allows inter-cultivation in two directions at right angles.
   • Formula for Tree Count: Area / (Row to Row × Plant to Plant).
2. Rectangular System:
   • Similar to square, but Row-to-Row (R-R) distance is greater than Plant-to-Plant (P-P) distance.
   • Pros: Accommodates more trees than square system; facilitates mechanical operations between wide rows.
3. Quincunx (Diagonal/Filler) System:
   • Essentially a square system with an additional temporary tree (filler) planted in the center of the square.
   • Fillers: Short-lived, early bearing plants (e.g., Papaya, Peach) removed once main trees crowd them.
   • Pros: almost doubles the plant population initially; utilizes space efficiently in early years.
4. Hexagonal (Septuple/Triangular) System:
   • Trees are planted at the corners of an equilateral triangle. A seventh tree is often placed in the center.
   • Pros: Accommodates 15% more trees than the square system.
   • Cons: Difficult to layout; cultivation is restricted to three directions; requires fertile land due to high density.
5. Contour System:
   • Used in hilly areas with slopes >10%. Trees are planted along contour lines (lines of equal elevation).
   • Pros: Reduces soil erosion and runoff.

B. Planting Density

This refers to the number of trees planted per unit area.

• Low Density: Traditional spacing (e.g., Mango at 10m × 10m). Large canopy, late fruiting.
• High Density Planting (HDP): Increasing plant population per unit area to increase productivity. Achieved through dwarfing rootstocks (e.g., M9 for Apple) or growth retardants (e.g., Paclobutrazol).
  • Example: Meadow Orcharding (Ultra High Density), often seen in Guava or Apple, with 3000+ plants/ha.

3. Training: Principles and Methods

A. Definition and Principles

Training is the physical technique of controlling the shape of a tree by directing its growth. It is primarily done during the juvenile phase (first 3-5 years).

• Objective: To create a strong framework (scaffold) capable of bearing heavy fruit loads without breaking.
• Principles:
  • Admit adequate sunlight and air to the center of the tree.
  • Control apical dominance.
  • Balance vegetative and reproductive growth.
  • Facilitate spraying and harvesting operations.

B. Methods of Training

1. Central Leader System:

   • The main trunk (central axis) is allowed to grow uninterrupted. Side branches grow at intervals.
   • Shape: Pyramid or Christmas tree.
   • Pros:Structurally very strong.
   • Cons: Lower branches may be shaded; tree becomes too tall for easy harvest.
   • Crops: Pear, Pecan.

2. Open Center (Vase) System:

   • The main trunk is headed back (cut) at a low height (60–75 cm). 3–5 scaffold branches are allowed to grow outwards. The center is left open.
   • Shape: Vase or Bowl.
   • Pros: Excellent light penetration; better fruit coloration; low stature.
   • Cons: Structurally weak crotches (prone to splitting under fruit load).
   • Crops: Peach, Apricot, Plum.

3. Modified Leader System:

   • An intermediate form. The central leader is allowed to grow for 4–5 years to generate scaffolds, then headed back.
   • Pros: Combines the structural strength of the Central Leader with the light penetration/low height of the Open Center.
   • Crops: Most commercial orchards (Apple, Mango, Citrus, Guava).

4. Pruning: Principles and Methods

A. Definition

Pruning is the judicious removal of plant parts (leaves, twigs, branches, roots) to influence the physiology and reproductive potential of the tree. It is done throughout the tree's productive life.

B. Basic Methods

1. Heading Back:
   • Cutting a branch back to a bud or a stub.
   • Effect: Removes apical dominance. Stimulates the buds just below the cut to break dormancy. Results in bushy, compact, vegetative growth.
2. Thinning Out:
   • Complete removal of a branch or shoot from its point of origin (base).
   • Effect: Does not invigorate new vegetative growth as much as heading back. Increases light penetration and air circulation. Used to remove water sprouts and crossing branches.

C. Special Pruning Techniques (Physiological Manipulation)

These techniques manipulate the Carbohydrate:Nitrogen (C:N) ratio and hormone flow (Auxins) to induce fruiting.

1. Girdling (Ringing):
   • Technique: Removing a circular strip of bark (phloem) from a branch or trunk without injuring the wood (xylem).
   • Principle: Stops the downward translocation of carbohydrates (sugars) produced in leaves to the roots. Accumulation of sugars above the girdle promotes flowering and fruit set.
   • Risk: If the wound doesn't heal, roots starve, and the tree may die. Commonly used in Grape and Litchi.
2. Notching:
   • Technique: Making a partial cut or removing a sliver of bark above a dormant bud.
   • Principle: Blocks the downward flow of Auxin (which suppresses lateral buds). Without the suppression, the bud sprouts into a vegetative shoot.
   • Purpose: To fill a bare space on a trunk with a new branch.
3. Nicking:
   • Technique: Making a cut or removing a sliver of bark below a bud.
   • Principle: Blocks the upward flow of water and nutrients/carbohydrates to that specific bud.
   • Purpose: To weaken a vegetative bud or keep it dormant, often to encourage fruit spur formation elsewhere.
4. Bending:
   • Bending branches downward causes accumulation of carbohydrates and ethylene, promoting flower bud formation (common in Guava).

5. Rejuvenation of Old Orchards

A. Concept

Orchards eventually become "senile"—characterized by crowding, intermingling branches, low sunlight penetration, high pest incidence, and declining yields. Rejuvenation restores their productive potential.

B. Steps in Rejuvenation

1. Heading Back: Main scaffold limbs are cut back severely (to 1.5–2.5m height) during the dormant season.
2. Protection: Cut ends are treated with Bordeaux paste or Copper Oxychloride to prevent infection.
3. Shoot Management: Multiple shoots will emerge from cut ends. Only desirable shoots are retained; others are thinned out.
4. Nutrient/Water Management: Integrated nutrient management and irrigation are increased to support rapid regrowth.
5. Intercropping: While the canopy regrows, intercrops can be grown to generate income.

Success: Common in Mango, Guava, and Citrus. Can extend orchard life by 10–15 years.

6. Top Working and Frame Working

These are techniques used to change the cultivar of an established tree (e.g., converting a seedling tree to a commercial variety or replacing an old variety with a new market-preferred one).

A. Top Working

• Method: The main branches of the tree are headed back severely (similar to rejuvenation). The desired scion varieties are grafted onto the remaining stubs.
• Techniques used: Cleft grafting, Bark grafting, or Patch budding on new shoots.
• Suitability: Best for younger trees or when the entire canopy structure needs re-doing.
• Disadvantage: Drastic shock to the tree; requires 2–3 years to return to fruiting.

B. Frame Working

• Method: The main skeletal structure (framework) of the tree is retained. Only small laterals and fruiting spurs are removed.
• Process: Hundreds of scions are grafted onto the existing framework branches throughout the tree (often 50–200 grafts per tree).
• Techniques used: Stub grafting, side grafting, or chip budding.
• Pros:
  • The tree returns to fruiting much faster (often the next year) because the large leaf area is restored quickly.
  • Less shock to the root system.
• Cons: Extremely labor-intensive and expensive due to the high number of grafts required.