Agriculture Reference
In-Depth Information
minimizing weed growth. Polyethylene sheet mulching of beds substantially
alleviates weeding within beds.
Weed control in commercial plantations is achieved by chemical means,
unless labour is abundant and inexpensive. Chemical weed control is ei cient
and rapid if done correctly at appropriate times, using mechanical applicators.
Pre-emergence application, either before or immediately after planting, is low
in cost and ef ective. For herbicides, as with other agricultural biocides, there
usually are restrictions on timing of applications and limits to the quantity
that can be used per hectare, per crop cycle or per year.
HARVESTING AND POSTHARVEST HANDLING
Harvesting
Prior to the use of chemicals to induce fl owering, many passes were required
to complete harvesting of a large fi eld, due to the wide variation in time of
fl owering during the winter season, when most fl ower induction occurred.
Chemical induction concentrated the period of fl owering, therefore
condensing harvesting to two to three passes (Paull and Chen, 2003). Natural
or precocious fl owering during cool weather with short days can signifi cantly
disrupt harvesting and marketing schedules. In Hawaii, fruit developing from
precocious fl owering in some years leads to a second peak, followed by a mid-
year dip in production (Fig. 12.10).
Controlled ripening of fruit with ethephon prior to harvest can further
reduce the number of harvesting passes. Ethephon is applied 48 h or more
before harvest to accelerate shell degreening (Soler, 1992). This accelerated
shell degreening is due to destruction of chlorophyll, giving the shell a
more uniform colour. The application should occur when natural colouring
has started, to assure good fruit quality, and is sometimes less ef ective in
hot weather.
Fruits destined for the cannery are usually harvested at the half- to three-
quarter-yellow stage. Fruit to be transported to distant fresh fruit markets is
picked anywhere from mature green (no yellow colour) to quarter-coloured
stage. Fruit maturity is evaluated on the extent of fruit 'eye' fl atness, skin
yellowing and acidity to total soluble solids (TSS) measurements. Consumers
similarly judge fruit quality by skin colour and aroma. A minimum reading
of 12% total soluble solids (
o
Brix) is required for fresh fruit in Hawaii, while
others have suggested 14%. A sugar to acid ratio of 0.9-1.3 is recommended
(Soler, 1992).
Pineapple for the fresh market is hand harvested, with pickers being
directed as to stage or stages (shell colour) of ripeness required. Fruit is
packed either in the fi eld or at a central packing shed. In Hawaii, pickers walk
