Agronomic management of kiwifruit: annual cycle and characteristics

Botanical Characteristics of Kiwifruit

Kiwi (Actinidia deliciosa var. deliciosa C. Liang and A. R. Ferguson) is a deciduous, climbing, and dioecious shrub, with male and female plants occurring separately.
It produces a berry-like fruit with numerous seeds and has a long lifespan: it is a perennial plant that can live for over 20 years in commercial plantations.

Kiwifruit root system: The root system develops mainly within the first 60 cm of soil.

• Low exploratory capacity
  High aeration requirement
  Succulent and strongly branched structure
  Susceptible to dehydrationVulnerability to nematodes of the genus Meloidogyne

Kiwi shoots: Shoots are vigorous but have certain limitations:

• They are brittle in the wind
  Very sensitive to frost during the first 30–45 days
  Tend to coil when in contact with other shoots or supporting structures, as part of their climbing adaptation

Kiwi flowers: Flowers are functionally unisexual.

• Borne in clusters of 1 to 3 on female plants, and up to 8 on male plants
• Despite being showy, they do not produce nectar.
• Pollen is light and dry, which complicates pollination by bees.

Kiwi fruit: Key fruit characteristics:

• Weight: 90–100 grams
• Pedicel scar closes slowly, making it susceptible to contamination by Botrytis cinerea (causing decay during storage)
• Highly sensitive to ethylene (even at concentrations as low as 0.01 ppm, which accelerates ripening)
• High vitamin C content

Floral initiation in kiwifruit:

• Flowers develop on the first 12 leaf axils of annual shoots emerging from the previous year’s wood
• Floral induction occurs between mid-January and April
• Visible floral differentiation occurs when sprouting resumes at the end of August, after adequate accumulation of winter cold and favorable thermal conditions
• It is common to observe floral aberrations (fan-shaped or flat fruits), which must be removed by manual thinning while still in the bud stage.

Stages of kiwi cultivation and agronomic management

Dormancy

Objective: Accumulation of winter cold

Agronomic management:

• Winter pruning
• Tying up shoots and structures

From Budbreak to Flowering

Physiological processes:

• Floral differentiation
• Natural bud thinning
• Shoot breakage due to wind action
• Agronomic management:
• Thinning of flower buds
• Controlled irrigation
• Fertilization with Nitrogen

Flowering

Key process: First peak in root growth

Agronomic management:

• Green pruning for vegetative control and flowering optimization

Rapid Fruit Growth

Critical period: First 50 days since fruit set

• Fruits reach 50% of their final weight and 75% of their final diameter

Agronomic management:

• Additional green pruning
• Fruit load adjustment
• Potassium fertilization to support development

Slow Growth and Maturity

Fruit evolution:

• Increase in root growth
• Fruits maintain between 4 and 4.5 °Brix
• Seeds change color from white to dark brown
• Once the 5 °Brix threshold is reached, soluble solids increase rapidly, especially with decreasing temperatures

Result: Activation of reserve accumulation
Agronomic management: Harvest at optimal maturity

Post-harvest

Key phase for the following season:

• Maximum accumulation of reserves
• Increased root growth

Critical management points:

• Trunk susceptibility to frost damage
• Leaf drop due to freezing
• Soil improvements (focused on porosity)
• Trunk protection in plants younger than 4 years (especially in female areas)