Date Palm
Phoenix dactylifera
Input from R. N. Pal
Deputy Director General (Horticulture), Indian Council of Agricultural Research
DATE PALM (Phoenix dactylifera)
is a highly nutritious fruit. It is rich in sugar, iron,
potassium, calcium and nicotinic acid. One kg fully ripe fresh
ripe fresh dates provide approximately 3,150 calories. The flesh
of dates contains 20% moisture, 50-65 % sugar, 2.5 %fibre, 2 % protein
and less than 2% each of fat, minerals and pectic substances.
Thus,
date fruit can help supplement the dietary needs of desert people where
very few nutritive foods are available. In California, diced
date, date paste and sugar are manufactured for use in breakfast and
bakery. The leaves of the palm also have potential for use in the
manufacture of paper.
Climate and soil
Date
palm is very exacting in its climatic requirement, which according to
an Arab saying should grow with its feet in running water and its head
in the fire of the sky. The successful cultivation of date palm
requires a long summer with high day as well as night temperature, a
mild winter without frost, and absence of rain at the time of flowering
and fruit setting with low relative humidity and plenty of
sunshine. It is estimated that finest date varieties require
3,300 units of heat (base 10`C) for full maturity of its berries.
The
heat unit summation must occur from pollination until full maturity of
berries. This period should be rainless and dry. This is in
contrast to its native home in Mediterranean region where summers are
dry with rainy winters to allow fruit development from May through
September –October. In Indian subtropics, fruiting period is
confined only from February-July whereas ripening period coincides with
rainfall. Therefore, fruits do not reach ripening stage and
should be harvested at earlier stage of fruit development.
Deep, sandy loam soils ideal for maximum water–holding capacity
and good drainage are desirable. Date palm can grow in alkaline
and saline soils but in such soils its growth and productivity are
greatly reduced. The soil profile should be free from stones of
calcium carbonate concretions and hard pan at least up to 2 m
depth. Date palm tolerate high soil salinity (pH 8-10). It
can survive in soils having 4 % salt concentration, provided the root
system does not come in contact with a stratum of soil where the
sodicity is more than 1%.
Varieties
More
than 1,000 varieties of dates are known to exist. However, only a
few of them are commercially cultivated in different
countries. Halawy, Khadrawy, Sayer, Barhee and Zahidi in Iraq;
Deglet Noor,
Medjool and Ghars in North African countries and Begam Jangi and Dhakki
in Pakistan are commercial cultivars. Of the date varieties
evaluated, Barhee, Halawy, Khalas and Khaunezi have a very little or no
astringency and are thus suitable for eating as raw. These
varieties can be harvested and used at doka stage before the onset of
rains. Date palm Medjool, Zahidi, Shamran and Khadrawy are
astringent at doka stage and can be used for processing to prepare dry
dates (chhuhara) and soft dates (pind khajoor). The red colored
dates Zagloul and Hayani are suitable for the preparation of date juice
(RTS) and other products like jam and chutney. The important date
varieties are:
Halawy
An
early cultivar, suitable for raw eating and processing as soft dates.
Tolerant to rain. Fruit small to medium, oblong with rounded apex
and yellow at doka stage. TSS 25.5-42.2% and astringency in fruit at
doka stage low or almost absent.
Khadarawy
A comparatively dwarf-and mid-season cultivar. Fruit matures
slightly later than Halawy. Small to medium, oblong-ovate and
greenish-yellow at doka stage.
Shamran (Sayer)
Mid-season
cultivar, slightly tolerant to high humidity. Fruit is medium to
large, oblong-oval and yellow at doka stage with faint longitudinal
streaks of red near the base.
Medjool
A
late-ripening cultivar, it is suitable for preparation of dry
dates. The fruit is large and broadly oblong- oval to somewhat
ovate, orange-yellow with a fine reddish-brown stippling and highly
astringent at doka stage. The seed has ridges.
Barhee
A
mid season or late cultivar. Fruit small to medium, ovate to
nearly round, golden-yellow and almost free from astringency even at
green stage. Hard ripe doka fruits very sweet and suitable for
raw eating.
Zahidi
A
mid-season and prolific–bearer, variety, slightly tolerant to
rain or high humidity because of smooth and hard surface. Fruit
small to medium, ovate and yellow, astringent at doka stage. Fruits are suitable to prepare soft dates.
Khalas
It
is a mid-season cultivar. Fruit small to medium, oblong oval,
yellow and sweet at doka stage, has an oblique base and irregular
outline. It is suitable for raw eating and for processing as soft
dates.
Wild date palm (Phoenix sylvestris):
This
grows wild in the mid hill region of the North West Himalayas and is a
very multipurpose tree.
Propagation
Date
palm is propagated by off- shoots (suckers) emerging from the base of
the palm. Since plants raised form seeds not only bear inferior
quality fruits but almost half of them may be non-bearing
males. The off shoots could be separated from mother plants 4-5
years after
planting. Thus, 8-20 off shoots of 8-15 kg size can be obtained
during its fourth and tenth year of life and none therefore. This
is obviously a slow rate of multiplication. Absence of a fast
multiplication technique for date palm is thus a prominent bottleneck
in its extension of area. About 30 million offshoots are required
to cover 0.3 million ha area in the arid north-west region. Although,
tissue-culture technique has been standardized in date palm, its
commercial use is still constrained owing to variation.
Prior to the removal of offshoots, the outer leaves are cut back to two
thirds of their lengths and the inner leaves to half. The stalks
of the pruned old leaves are tied together to protect the tender apical
growing bud. It is ensured that offshoots have well
–developed root system. The offshoot separated by cutting
the connection with the help of a sharp chisel in such a way that no
injury is caused to the mother palm. The copper fungicidal paste
should be applied to cut end of the off shoot.
Research is in progress to induce rooting to establish small sized off
shoots and to induce more number of off shoots/ palm. Application
of IBA to small offshoots before removal from mother palm and then
putting them in mist is quite effective in footing and survival
percentage. The other vegetative them methods- cutting, grafting,
budding and layering are not successful.
Cultivation
Planting:
Date palm is a perennial tree and bears fruits for 40-50 years.
Therefore, adequate planting distance is very essential. In
general, planting is done at 8 m distance between rows and plants in
square system, which facilitates intercultural operations and proper
development of the palms. A total of 156 palms are accommodated
in one hectare. Since it is dioecious, 10% of these must be raised by
planting male offshoots to provide adequate pollen-grains.
The field should be thoroughly ploughed, leveled and pits of 1m x1m x
1m size are dug during simmer. They are kept open for about a
fortnight and refilled with a mixture of garden soil and well
decomposed farmyard manure. Care should be taken that the crown
of the planted offshoots remains at least 10-15 cm higher than the
ground level so that the irrigation water does not touch it or enter
into it. Young offshoots should be protected against intense heat
and low winter temperature for at least 2-3 years by providing partial
shade. Rainy season (July-September) is ideal time of planting.s
Regulating leaf number:Sufficient
number of green leaves is necessary for growth, development, and
yield. Insufficient number of leaves results in low quality
fruits and lesser inflorescence in the following spring. About
75-100 leaves are in Khadarawy, Zahidi, Barhee, and one to every 8-9
leaves in Halway, Deglet Noor and Dayri. Further, 12 leaves/
bunch is optimum leaf-bunch ratio in Barhee dates. Optimum yield
and good quality fruits could be obtained with 8 active leaves /bunch
when 5-8 bunches/ plant are retained. The old and senescing
leaves should be pruned. Time of leaf pruning is June. It
is better than in February. To facilitate pollination and
subsequent handling of bunches, the spines from the leaves around
bunches are also removed in the late winter to early spring.
Pollination: Date
palm is highly cross pollinated due to its dioecious nature. In
commercial plantation, mechanical or hand pollination is done. For this, 2-3 male trees are enough to pollinate 100 female
palms. About 2-3 strands of male flowers are inserted between the
strands of female flowers. Since metaxenia is common in date
palm, selection of a good pollenizer is important. The quality of
date fruits, particularly fruit size and time of ripening are
influenced by pollen. Under Indian conditions, early ripening is
desired to avoid losses due to rains. If the male spathes open
earlier than female, the pollen is dried and stored for use at a later
date. Dried pollen containing about 10% moisture can be stored
satisfactorily with calcium chloride at room temperature for 2-3
weeks. It can be stored until the next season in refrigerator at
about 4`-5`C. However, fresh pollen produced the best fruiting,
followed by that with refrigerated pollen and pollen stored at room
temperature. Trailor mounted palm dusters are used in USA. When
pollen dust is used, dusting has to be repeated 2-3 times.
In India, spathes generally emerge during February-March and the flower
opening starts during March-April. Although stigma of female
flower remains receptive for several days, it is better to pollinate
the inflorescence as soon as they crack open.
Fruit thinning:
Fruit thinning is necessary to ensure adequate flowering in the
following year, to improve fruit quality, prevent delayed ripening and
reduce compactness and increase ventilation of the
bunches. Thinning can be done manually of by chemical sprays.
Manual method is
common which involves removal of some bunches or strands from each
bunch or shortening the length of strands. The number of fruit
that a palm can sustain depends on variety, age, vigour and number of
green leaves. Three to four bunches/palm is recommended from
fifth year onwards. In India 8-10 bunches are left on each
palm. The best results are obtained by removing one third strands
from the
centre of the bunch. However, in long stranded variety, Deglet
Noor, shortening of the strands is also necessary.
Plant growth regulator ethephon is an effective fruit thinning agent.
It provides additional benefit in inducing early ripening of
berries. This is of great significance in India, as harvesting of
fruits before the onset of rains is advantageous. Ethrel at
500-1,000ppm encourages early ripening.
Manuring and fertilization: Nutrient
application is important for satisfactory production of quality
dates. A dose of 30kg N, 20kg P and 50 K/ha should be
applied. However, in India, application of 1.36 kg N/tree is
necessary. Manures can be applied in the beginning of winter
season and the fertilizers in March/ April. However, an adult
tree should be fed 600 g N, 100 g P and 70 g K per year. The
application of K and P should be monitored according to soil
conditions. Application of 12.5 -35.2 tons/ha of farmyard manure
is beneficial.
Intercropping:
In
areas where irrigation facilities are available, intercrops can bring
handsome returns. Preference should be given to lentil, gram, peas and
senji in winter and mash, green gram (mung) and black gram for
summer. Suitable vegetable crops can also be taken with adequate
manuring. Small- sized fruit trees like pomegranate, phalsa and
papaya can also be grown between date palm. However, under such
conditions, additional requirements of water and nutrients for the
intercrop should be provided.
Irrigation:
Irrigation
is very essential in date palm because it is grown in hot and dry, low
rainfall areas. Further, the water requirement of date palm is
high although it can withstand prolonged droughts. Date palm
likes wet feet but is damaged under prolonged stagnation. In high
water table areas, 4- 6 irrigations in a year may be
adequate. Light and frequent irrigations must be given after
planting. Mulching may be useful at this stage. In sandy
soils, irrigation
may be given everyday or on alternate days. The frequent
irrigations is reduced after the offshoots have established which is
dependent on soil texture and weather conditions.
About 10- 12.5 acre cm of water is required to grow palms where the
soil is dry during ripening and 6-8 acre feet where heavy water is
continued throughout the year. Mulching with black polythene or
available organic mulch materials like date palm leaves or weeds in the
basin helps conserve moisture and increase irrigation interval.
Harvesting and postharvest management
The
dates are eaten at different stages of maturity depending upon the
varieties and thus harvested at different stages according to local
demand, customs and climate. In India where maturity coincides
with monsoon, fruits are harvested at ‘doka’ stage to avoid
spoilage due to rains and high humidity. Spraying of
Ethephon (1,000ppm) at color break stage is recommended in
Gujarat to advance maturity. Under Mediterranean climate, they
are allowed to ripen fully before harvesting. It is stored after
drying. Fruits for fresh eating are preferred at
‘Dang’ stage but handling of such fruits is difficult.
Date palm trees usually take approximately 6 years for commercial
bearing yield is comparatively less during initial years but it
increase with age. On an average, 50 kg doka fruits are produced
from each palm of 10 years age increasing to 75 kg at the age of 15
years. However, the yield also depends upon variety, cultural
practices and other factors.
The dates harvested at doka stage have 70-80 % moisture. They
have very poor keeping quality. Therefore, these fruits should be
marketed soon or may be cured or processed. Since Doka or dang
fruits cannot be stored for future use, curing should be done. Doka
fruits are successfully processed to prepare Chhuhara. The
technique involves boiling fruits for 5-10 min. Depending on
cultivar and then dehydration, in solar dryers or in air circulating
ovens at 48-50 C for 70-95 hr, the doka fruits can also be artificially
ripened to bring them to the final stage of maturity by dipping them in
boiling water for 20-25 seconds and then dehydration in oven at 38 C-40
C.
The date juice
and sugar have been successfully utilized as sweetening and flavoring
agent in ice cream. Recently attempts have also been made to can
date pulp and khalal fruits in 20-40% sugar syrup. A satisfactory
pickle is obtained after 6 weeks of pickling green fruits treated with
15 % sodium chloride and 2% acetic acid.
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