Agriculture Reference
In-Depth Information
Calendar date is the simplest, and where growing conditions are relatively
stable can be used to predict the likely harvest date for each cultivar in each
locality based on past experience. However, the date of blossoming varies with
pre-bloom temperatures from year to year (see Chapter
) and the rate of fruit
maturationisdependentontemperaturesduringthegrowingseasonespecially
in the early part of this (Eggert,
). Regression
studies have shown that the optimum harvest date can be predicted in the
majority of years from the date of
; Warrington
et al.
,
% full bloom and summer temperatures
(Luton and Hamer,
).
Attainment of appropriate levels of maturity is, however, affected by site fac-
tors, e.g. aspect and altitude, which can affect temperatures, and by tree factors
including rootstock and pruning, which influence exposure to light and also the
age of bearing wood. Site and tree factors influence the date of blossoming and,
as Blanpied and Little (
) have shown, the chronologically oldest fruits that
develop from the earliest blooming flowers are the most advanced in maturity
if all fruits are harvested at the same date. Assessment of the best time to harvest
the fruits is therefore made on an orchard-by-orchard basis. South African pro-
cedures (van der Merwe,
a) illustrate methods used to determine harvest
dates for apples and pears intended for long-term storage for export. Starting
from
weeks before the historical optimum picking date for the cultivar, fruits
are collected at first weekly, then twice-weekly, and seven maturity indices
recorded:
Fruit firmness (kg)
Skin colour on a scale of
to
(background green colour)
Seed colour on a scale of
Titratable acids (g malic acid/
to
g juice)
Total soluble solids (%)
Starch conversion (% white surface)
Days from full bloom
These are then evaluated against average maturity indices relating these char-
acteristics to the optimum maturity for harvest (Table
.
).
Control of ripening and senescence
Quality is optimized by harvesting at or near to ripeness for immediate con-
sumption, or before this horticultural maturity in order to accommodate the
developmental changes that will take place during storage, transport and mar-
keting (Fidler,
).
