Tamarind monograph.pdf - Crops for the Future

9.2 Harvesting stage
In the Philippines fruits are harvested at two stages, green for flavouring and
ripe for processing. The fruits of sweet types are also harvested at two
stages, half-ripe and ripe. At the half ripe stage the pulp is yellowish green
and has the consistency of an apple, particularly in the case of sweet forms.
At the ripe stage, the pulp shrinks, due to loss of moisture, and changes to
reddish brown and becomes sticky.
In most countries, the sour tamarind ripe fruits are harvested by shaking the
branches and the pods are collected on a mat. Sweet tamarind pods fetch a
high price both in local and foreign markets and are carefully harvested by
hand picking. Sometimes bamboo ladders are used to pick the fruits. If the
whole fruit is marketed, both sweet and sour types should be harvested by
clipping to avoid damaging the pods (Coronel, 1991). The use of poles in
picking is not desirable as knocking can cause damage to the pods.
Generally, the fruits are left to ripen on the tree before harvesting, so that the
moisture content is reduced to about 20%. Mexican studies reveal that the
fruits begin to dehydrate 203 days after fruit set, losing approximately half
of the moisture. When the fruits are left unharvested they may remain
hanging on the tree for almost one year after flowering and eventually
abscise naturally. Sometimes they remain on the tree until the next flowering
period (Chaturvedi, 1985).
9.3 Yield
The yield of tamarind varies considerably in different countries, depending
on genetic and environmental factors. Feungchan et al. (1996 a) reported
that the fruit yields are influenced by environmental and genetic factors, but
the age of the tree is not correlated with fruit yield. The size of the tree is
obviously a factor however, and older trees which have had many years to
mature, would be expected to be larger and so produce a greater yield. Age
of bearing is important in relation to profits. Reports of very long juvenile
periods over 4-10 years are probably because they were recorded on
unselected materials.
Usha and Singh (1996) reported that cross-pollination results in higher fruit
set and retention in tamarind than when open or self-pollinated. Bees are
known to pollinate tamarind, and bee farming could provide additional
income to farmers. Fruit set is influenced by environmental factors, such as
age and size of shoots, carbon : nitrogen ratio and the hormonal balance
under which the trees are grown. Due to the influence of these factors, high
seasonal and annual yield variations can be expected.
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