Agriculture Reference
In-Depth Information
Transplanting and plant spacing
After about 6-8 weeks in the nursery, the seedlings should reach the eighth
to twelfth-leaf stage and are most suitable for fi eld planting. In rainfed areas,
fi eld planting is done at the beginning of the rainy season. Seedlings grown
in pots and bags are planted directly, with the removal of the pot or bags.
Transplanted plants must be watered soon after planting to settle the soil
around the root system.
Spacing between plants and between rows varies widely. Universally
practised is the single-row system, with between plant spacing ranging from
1.8 to 3 m and between row spacing varying from 1.8 m to as much as 3.6 m
(see Fig. 3.7b). The between-row spacing largely depends upon degree of
mechanization; a standard tractor requires
ca
3 m. The most frequently used
spacing is 2.0-2.5 m within row × 2.5 m, giving a density of 1600-2000
plants/ha. The double-row system, with 2 m between a set of rows and 3.5 m
between double rows, is used. Normally, two or three seedlings are planted
in each hole, spaced about 30 cm apart. When the plants start fl owering,
the female plants are removed, leaving only one hermaphrodite plant per
point. Polyethylene mulch over the beds prevents moisture losses and greatly
minimizes weed growth within the beds (Fig. 3.7b). Organic mulches of
grasses, wood shavings, rice hulls or other kinds of material are also benefi cial.
Irrigation
Non-irrigated fi elds in Hawaii are located in a region with 2500-3125 mm
of rain, fairly well-distributed throughout the year. However, occasional
droughts of 2 or 3 months occur. Low soil moisture tends to shift the sex type
to male and results in lower fruit yields, while high moisture levels can lead to
excessive production of misshaped carpellodic fruit, with rapid tree growth.
Dioecious cultivars fare better unless moisture stress is severe. A monthly
minimum rainfall of 100 mm is needed without supplementary irrigation
for some production. Irrigation should replace at least the moisture lost by
pan evaporation, and 1.25 pan evaporation is required for maximum yield of
mature trees (Fig. 11.9). Young trees only need about 0.3-0.5 pan evaporation.
Good production occurs with 60-90 l/tree/week immediately after planting or
during the wet season and 120-240 l/tree/week during the dry period.
Irrigation may be by fl ooding between the row space by furrows running
along both sides of the rows of trees or via microsprinklers or jets or drip.
Irrigation intervals of around 10-15 days may be necessary to sustain
production, unless this interval is broken by rainfall. Papayas are wind-
pollinated, and overhead sprinkling reduces pollen dissemination and
therefore is not recommended. A drip system must be capable of providing
the maximum amount rather than average demand. If a tree requires
