CHAPTER TWO
2. LITERATURE REVIEW
2.1 Date palm (Phoenix sylvestris Roxb.)
Date palm is a prominent tree of the desert oases.Date palm is common through India Srilanka and Bangladesh. Consequently Date palm husbandry is a traditional land use practice through the world since ancient times (Blatter, 1978). Date palm is sometimes carelessly or erroneously called as date palm. But in its true sense it is wild date palm or date sugar palm as were known from the many writings. It is at best grows to a height of 7-16 m (Anon, 1987). According to Blatter (1978) it was mainly cultivated in India where numerous terminologies evoked for it. As for example, in Hindi it was known as:Sendhi, Kejur, Hager, Khaji, Salma, Thalma, Thakil; in Bangla; Kajar, kejur, etc. It is also termed differently by various tribal of India for instances, Khejur in (kol); Khijur, (Santal);Sindi, (Gold);Khajur, Khaji, (Panj.); seindi,(Berar); Sendi, K-hajura, K.hajuri,(Bomb.); Boichand, sedri, shindig (Mar); Kharak, (Guz); Sandole-ka-nar, (Dec); Itchumpannay, Periaitcham, ltcham-nar,tham pannay, (tarn); Ita, Pedda-ita, Itanara, Ishachedi, (Tel.);Ichal, Kulu, Ichalu mara, (Kan); Kurjjuri, IChajura, Madhukshir, (Sans).
2.2 Area of origin and Distribution:
It grows a wide belt from the Atlantic Ocean through the Sahara, the Arabian Peninsula, into Iran and the Indus Valley in Pakistan with their main centers of production. Outside this belt the concentrations are much more localized and except for the U. S. of less importance worldwide (dowson, 1982).
Date palm is believed to be indigenous to countries around the Persian gulf. Its culture was probably established as early as 3000 BC in Iraq (Mesopotamia). It has also been under cultivation in Egypt since the prehistoric days but here it assumed importance sometime later than in Iraq. Excavations of Mohenjodaro revealed that this fruit was in Indo-Pakistan as early as 2000 BC, In the Old World the regions where dates are grown commercially in large quantities stretch from Indus valley in the East through the southern edge of the Turko-perso-Afghan mountain, Iraq, Kirkuk-Haifa oil pipe and along the coastline up to Tunisia and then skirting the southern edge of the Atlas to the Atlantic. Southwards the date lands fall up to Sudan then follow the coasts of the Red sea and Gulf of Aden northern part of Somalia and southern coast of Arabia. Date palm was introduced into the western hemisphere in the late eighteenth or early nineteenth century by the Spanish, missionaries.
Dates were also introduced in the Atacama desert and other parts of South America, Kalahari desert of South Africa and the Great Central desert of Australia.
At present, the principal date growing countries of the world are Iraq, Saudi Arabia, Algeria, Iran, Egypt, Libya, Pakistan, Morocco, Tunisia, Sudan, USA and Spain having about 60 million palms. Of these, about one-thirds population is in Iraq.
In the Indus valley, date palm is believed to have been introduced by the soldiers of Alexander the Great in the 4th century BC and also by the Moslem invaders at the beginning of the 8th century AD. Almost all of these areas are now in Pakistan. There is no commercial plantation of good dates in India. Wild groves of seedling date palm are found on the coastal belt from Anjar to Mandvi in. Kachchh district of Gujarat (Pareek, 1984). Date palm groves on the north-western border of India have developed from seeds thrown by army camps and partly from seed; and offshoots planted by the settlers (Pareek and Sodagar, 1986). Kachchh groves are believed to have been raised by the plant material brought by the Turk settlers during their visits to the Middle East countries for Haj or for trade. These groves may be about 200 years old. It is estimated that about 1-3 million palms are growing on this coastal belt producing about 33,000 tonnes of dates per year. Introduction of some commercial cultivars of date palm from the USA, Pakistan and the Middle East countries were made during 1955 to 1962 at Regional Fruit Research Station, Abohar, under the aegis of the Indian Council of Agricultural Research. Further importation of date suckers was started since 1978 under the All India Coordinated Research Project on Arid Zone Fruits of the ICAR at Bikaner, Jodhpur and Jaisalmer in Rajasthan, Abohar in Punjab, Hissar in Haryana and Mundra in Gujarat.
In India, dates are almost exclusively imported from the Near-East and North African countries where it is the mainstay for the economy. Date has been a staple food of the population extending from western Iraq across Arabia and North Africa
2.3 A brief view of date Palm:
It is a very graceful palm, when not injured by extracting toddy and it attains at best 30-50 feet high (Blatter, 1978). Trunk rough from the persistant bases of the leaf stalks. Crown hemispherical, very large and thick, leaves 10-15 feet long, grayish green, quite glabrous, pinnate; petioles compressed only towards the apex, at the base bearing a few channeled triangular short spines reaching 4 inches. Pinnules very numerous, densely fascicled, 6-8 by Va inch long, glaucous, rigid, uniform, conduplicate at the base, then canaliculaled, absolutely acuminated, almost spinous pointed, 2-4 farious, some intermediately spreading, others crossing these above and below in an ascending direction. Male flowers white, scented; spadix 2-3 feet long, erect; peduncle highly compressed. Spathes of about the same length, very coriaceous, almost woody, scurfy, separating into two boat-shaped valves. Spikes very numerous towards the apex of the peduncle, especially on its anterior face, generally in fascicles and simple, 4-6 inches long, slender, yellow, with a terminal stigma, surrounded at the base by the perianth flexuose. Flowers lA-PA inch long, very numerous, angular, oblique. Calyx cup-shaped, with 3 short rounded teeth. Petals three or four times longer than the sepals,
concave, warty on the outside, on the adnate, shorter than the petals. Female flowers distant, roundish. Calyx cup-shaped, obsoletely 3-toothed. Petals 3, very broad, convoluledly imbricate, having a small opening at the apex. Staminodes 3-4. Carples 3, free, erect; ovules solitary; style recurved, inwardly papilose. Fruiting spadix 3 feet long, nodding at the apex from the weight of the fruit, much compressed, of a golden orange color. Fruit scattered on long pedulous similarly colored spikes,1-1/4 inch long, oblong-ellipsoid, orange.
2.4 Scientific classification:
Kingdom :Plantae
Division :Magnoliophyta
Class: Liliopsida
Order: Palmaceae
Family :Palmae
Genus: Phoenix Roxb.
Species: Phoenix sylvestris(Roxb)
.
2.5 Botanical description:
A brief description of Phoenix sylvestris which is mentioned below:
2.6 Stem:
Straight covered with scars and remains of withered leaves and so it is a single stemmed tree going as high as 30m with an umbrella like canopy of green foliage.
2.7 Leaves:
Simple, pinnate, 45-60 cm long, narrow, stiff, born in pairs, upturned.
2.8 Inflorescence and flowers:
Inflorescences are spadix.. Flowers are small yellow born in clusters of 6-20 appearing on a mature tree. Only female cluster produces fruit.
2.9 Fruits and seeds:
Fruits are berry with fleshy pericarp which is sweet and edible, size 3-5cm. Cylindrical or oblong-ellipsoid, broeneolor with a smooth, thin but slightly thick skin. Seeds arc cylindrical, about 2-5cm long, hard endosperm and a small embryo, has a single groove, light to dark brown in color, often pointed on one end.
2.10 Cultural practices and Habitat:
Propagation by fresh seeds and suckers are commonly practices. Mostly plants are multiplied by suckers as it is easy and the fruits borne on this tress are of uniform size and of good quality suckers are grown in nursery for 12-18 months before being transplanted during rainy season. Spacing is 6-8
It is widely distributed in the whole of Africa (Except the palmless regions), the South-African floral region and the East-African islands; Arabia; Western Asia in the region of the Euphrates and Tigris, through India to the Sunda Islands and Cochin China. It is usually cultivated and of course, common throughout India.
However, observation revealed that it was not uncommon in the siwalik tract and the outer Himalaya and often associated with Pinus longifolia, reaches up to 5000 feet in Kumaon, with stems 40-50fect high and it forms extensive forests in Rohilkand, on the low ground which intersect and drain the rocky undulating granite hills; Ghiaunla in Ghawai at 3500 feet, banks of the bias above Mandi and in the jamu hills at 2000 feet elevation (Blatter 1978). It was commonly planted and self sown in most parts of India and Ceylon, except in sind and South Punjub, where, P. dactylifera takes its place. It is most abundant in Bengal, Behar, on the Coromandel Coast, and in Guzrat. In the Bombay Presidency it is common in moist ground throughout the dry districts, usually along banks and in the beds of streams and watercourses.
2.11Date palm production in Bangladesh:
Date palm is produced over the country in Bangladesh as homestead crop; however, in Bangladesh Khejur tree is grown in crop fields, homestead areas and marginal lands along the roads, canal and roads (Rashid, 1991). In the crop fields the palm is found on the ails (Slightly raised embankments that is used as boarder of crop fields); and also found within the field along with other crops (Abedin and Quddus, 1991).
Pounded and mixed with almonds, quince seeds, pistachio nuts, spices, and sugar its forms a restorative. A paste formed of the kernels and the root of achyranthes aspera is eaten with betel Products obtained from Date palm.
2.12 Juice:
In Bangladesh it was grown in many districts, profusely in jessore where it found a considerable importance due to the extensive use of its sap in making sugar (Blatter, 1978). The sap of Phoenix syivestris is also a good source of vitamins of the B group and contains in addition an appreciable amount of ascorbic acid (Rangaswami, 1977).
2.13 Leaves:
From the leaves bags, basket, brooms, fans etc. are made. The footstalks, after being beaten are converted into ropes for drawing water from wells. The fibers are plentiful, soft, bleach well, and are very well adapted for the use of paper makers.
2.14 Fruits:
The fruit is of an inferior kind and only eaten by the poorer classes, or used as medicine leaves as a remedy for ague.
2.15 Sugar of date palm:
Sugars from palm trees such as Phoenix syivestris and Borassus flabellifer are reported to be more nutritious than cane sugar (Rangaswami, 1977; Roy, 1951 cited by Morton, 1988). In Bangladesh, the industry of sugar made from Phoenix syivestris is an old one and date sugar was reported as largely manufactured and exported at the end of the eighteen century. In the middle of the last century, after slave emancipation measures gradually decreased the supplies of sugar from the West Indies, a rapid rise in date sugar production occurred. In 1849, one fifth (10,000 tonnes) of the whole annual quantity of sugar exported from India to England was date sugar (Annett, 1913).
2.16Age of Tapping:
Phoenix sylvestris can be tapped at a rather early age when the trees are 5 years. The number of the years a palm tree can be tapped is very different depending on the species. Phoenix sylvestrics can be tapped for more than twenty years (Abedin et al, 1987). Some species are able to produce sap all year round, but Phoenix sylvestris produce only seasonally (Crevost and Lemarie, 1913; Annett, 1913)
2.17 Tapping Technique:
The stttThe stem is pierced up to the terminal bud (Kovoor, 1983). In Bangladesh, the oldest leaves are removeremoved of October on one side of the palm tree along about 35cm. The bases of the petioles and the sheaths are carefully removed. A triangle piece of bark is cut but great care must be taken not to expose the sap-supplying inner zone. A week later, as the fine covering of soft tissues gets a little hardeh crack; this covering is removed without damaging the inner zone. Then comes a rest of 12 to 14 days after which a lateral incision is done in the triangle. The sap exuding from the scoope surface is run through a bamboo spout into a vessel. A new incision is made the 2 following days and then there is a 4-day period of rest and the same cycle is repeated until the heart is reached. The following year, the same treatment is done on the other side of the tree which gives a zigzag configuration lo the trunk; tapping can be practiced every year for several decades (average of 25 years) (Fealy, 1925; Annett, 1913; Barreveld, 1993). In order to slow down the fermentation of the sap, the earthen vessels arc coated with lime, in Bangladesh, they are well smoked every morning (Annett i913). tthe juice is allowed to run during the night. The juice so flowing is the strongest and best, and is called jirin juice. In the morning the juice collected in a pot hanging beneath the bamboo spout is remove and the heat of the sun causes the exuding juice to ferment over and shut up the pores in the tree. So in the evening new cut is made, not nearly so deep as the last, but rather mere paring, and for the second night the juice is allowed to run. This juice is termed do-kat and is not quite so abundant or so gooa the jirin. The third night no new cutting is made, but the exuding surface is merely made quite clean, and the juice, which then runs, is called jarra. It is still less abundant and less rich then the do-kat, and towards the end of the season, when it is getting hot it is unfit even for sugar manufacture, the gur mafrom it being sold simply as "droppings". These three nights are the periods of activity in the tree, an after these three it is allowed to remain for three nights at rest, when the same process again begins. Of course, every tree in the same grove does not run in the same cycle, some are at their first, some atheir second night, and so onn; and thus the owner is always busy.
As to the produce of one tree, one may expect from a good tree a regular average of five seers per night (excluding the quiescent night).
The colder and clearer the weather, the more copious and rich will be the produce. In the beginning of November tapping has began. In December and January the juice flows best, beginning as early as 3 p. m., and dwindles away as the warm days of March come. The juice of the date palms is largely turned into gur (molasses) by being boiled in a vat. A special variety is the patali, a hardened circular cake of molasses generally consumed with rice and mil.
2.18 Composition and uses:
It provides nutritive fruits rich in sugar, iron, potassium, calcium and nicotinic acid. Small amount of protein, copper, magnesium, chlorine, sulphur, vitamin A, and E2 are also present in date pulp. The flesh of dates with a moisture content of 20 per cent contains from 60-65 per cent sugar, about 2-5 per cent fibre, 2 per cent protein and somewhat less than 2 per cent each of fat, mineral matter and peptic substances (Nixon and Carpenter, 1978). Such fruits provide about 3,150 calories per kg.
In Iraq, alcohol, a liquor known as arak, vinegar, liquid sugar, date juice known as dibbis from the date pulp and a concentrate protein for poultry birds from date stone are manufactured. In California, diced date, date paste and sugar are manufactured for use in breakfast and bakery items. The leaves of the palm also have potential for use in the manufacture of paper (Frers, 1983).
2.19 Soil and Climate:
SOIL:
Deep sandy loam soils are considered best for date growing. However, dates can be grown in wide range of soil types. 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. Dale groves have been raised in the sandy and shallow soils underlain with murrain (kankar) at a depth of 50-100 cm in the Thar Desert of India. Date palm groves are also found in the coastal soils in Kachchh.Dale palm can tolerate high soil salinity. It can survive in soil having 4 percent salt concentration, provided the root system does not come in contact with a stratum of soil where the sodicity is more than 1 per cent (Ahmad and Farooqui, 1972).
CLIMATE
Successful date culture requires moderate winter temperature and long hoi summer to mature the fruit; it can withstand summer temperature as high as 50°c| Date leaves are injured by prolonged temperatures of ~670C or below. Serious! Defoliation occurred in Arizona at temperatures of — 10° to -8°C with duration of 12 hours (Tate and Hilgeman, 1962). The ideal mean temperature daring flowering and ripening of fruit is between 25-29c'C, depending on cultivar. For successful] fruit maturation, nearly 3000 heat units (above a base 10°C) are required. The heat units available in most of the north-western districts of India, counted from the time of dowering (end February) to July, indicate that these are suitable for date palm cultivation (Pareek, 1984). The summation units during this period at Jodhpur Bikaner, Ganganagar, Barmer, Jaisalmer and Bhuj add up to 3,245 ; 3,398 ; 3,309 | 3,274 ; 3,202 and 3,061, respectively.The home of date palm is in the Mediterranean region where practically no rai occurs during February to September and thus its fruit matures up to pind or tamar stage in about 180 days. There is no location in India which meets the requirement although fairly dry conditions are available in north-western India The number of days available for fruit development in Indian districts is cut short to 122-170 days (Table 3}, as the growers are obliged to harvest early to protect fruit spoilage owing to rainfall and high humidity, even though the fruits are not fully mature (pareek, 1984)
Early introductions of date palm at Abohar, having an annual rainfall of 260 mm, have met with these problems although possibility of good production of dates up to doka stage of maturity for fresh market and processing to prepare chhuhara has been demonstrated.
Protection from rain damage is done in California and Arizona by ventilation of bunches and covering them with was paper covers, open at the bottom (Tate and Hilgernan, 1962; Nixon, 1969). At Abohar, alkathene covers proved better than wax paper covers (Jawanda, 1974).
2.20 Propagation:
Date palm can be propagated by seed or by offshoots. Seedlings have a longer juvenile phase, and flower only when 4-10 years in age and result in nearly half female palms which bear fruits of variable quality. Propagation of commercial cultivar is, therefore, always done by offshoots. The offshoots develop from the axillary buds are emerged out of the fibre sheath in a few years (Bouguedoura, 1983), during the juvenile stage of the-date palm. At adult stage, most of these buds are inflorescential and thus few or no offshoot emerge. After 3 to 5 years of attachment to the parent palm, the offshoots produce roots and start producing second generation of offshoots, they are then ready to be removed (Nixon, 1969). At Abohar, after 4-6 years of planting about 2-3 offshoots could be removed every year for a period of 8-10 years and none thereafter (Bakhshi and Dhillon, 1962). At Jodhpur, offshoots could be separated 4-5 years after planting (Pareek and Muthana, 1978). A single palm may thus yield 10-25 offshoots during its first 10-15 years.To promote rooting, the base of the offshoot should be in contact with moist soil for at least a year prior to separation. It can be done by mounding or by putting soil boxes on the offshoots arising high on the trunk. The percentage of success in establishment largely depends on the size of offshoots, presence of roots on them, their preparation before separation and planting, season of separation and planting, etc. Toutain (1966) found that the success generally increased with increase in the weight of offshoots from 3-25 kg. Nixon (1969) recommended that the weight of offshoots ready for separation should range from 19 to 45 kg having maximum diameter of 20-35 cm depending upon cultivar, and it would be safer to leave an offshoot a little longer on the parent palm than to remove it before it is mature and - well rooted. Tatc and Hilgeman (1962) recommended that the offshoots should be 'separated when 25-30 cm in diameter and 15-32 kg in weight. At Abohar, offshoots of medium weight (12-16 kg) range proved better than those in the low weight (8-12 kg) range (Jawanda and Kalra, 1972).Small offshoots can be induced to root by the application of IBA before removal 1 from the mother palm and then putting them under mist (Reuveni et a!, 1972)Mohammed (.1978) concluded that propagation by mature basal shoots was the only method at present widely used commercially, but propagation by small-offshoots under mist showed promising results.
Date palm plantlets have been initiated from clonal explants via embryogenic callus and successfully transplanted to soil (Mater, 1986; Gabr and Tisserat 1985), Rhiss et al (1979) obtained plantlets with better root system from shoot tip off- shoots when cultured on a supplemented MS medium. Khan et al (1983) cultured' tissue explants consisting of shoot apex, primordial leaves, mantle meristem and ' roots on RM-1965 medium containing sucrose 3%, agar 1%, myo-inositol 100 mg/I and thiamine 0-4 mg/1. IAA, NAA, IBA and cytokinin were added to the basal medium at varying concentrations. NAA at 1-10 mg/1 with cytokinin-induced callus growth and root initiation.
Piantlets were obtained by reculturing explants on a medium containing NAA (1 mg/1) with cytokinin (0-1 mg/1). In India, also a somatic embryogenesis technique for regeneration of normal plants of Khadrawy and Medjool date palm cultivars from axillary buds, using a modified MS medium containing activated charcoal, 2, 4-D and BAP has been standardized (Sharma et a!.,} 1984, 1986). Hardening of selected plantlets, having well-developed tubular stem' soaked in 0'05% Bavistin and grown in pots with well-drained sterilized soil, was] done by creation of fog around them for at least 6 weeks, careful watering and application of nutrient solution for 2-4 months and gradually lowering the humidity by i intermittent exposures (Sharma and Chowdhury, 1986). The plants were then' successfully transplanted in the field.
2.21 Cultivation:
Planting:
In California, the best time to remove and transplant offshoots is after the soil begins to warm up in the late spring and early summer (Nixon. 1969). At Arizona,! Offshoots removed and planted during May and June had fewer casualties and made better growth than those planted in the late summer, fall or winter (Tate and Hil- geman, 1962). Spring planting took full advantage of the summer growth period. At Abohar, the offshoots removed in March-April survived better in direct field! planting than those removed in August-September (Bakhshi, 1972). However, the separation could be done both in February-March and August-September.
The offshoots are cut from the parent palm by means of a specially designed chisel. No green leave should be removed from an offshoot until it is cut from the parent palm as its growth will be in proportion to its leaf area (Nixon, 1969). After the removal of offshoots, old leaf stubs and lower leaves are cut off close to fibre, the basal 60-120 cm of offshoots being left bare of leaves so that the youngest' 10-12 leaves around the bud are retained (Tate and Hilgeman, 1962 ; Nixon, 1969). .
Planting distance depends upon the cultivar, texture and fertility of soil ant the means of irrigation. The offshoots are planted 9 m apart in Coachella Valle" and in Arizona (Tate and Hilgeman, 1962 ; Nixon, 1969) and 5-8 m apart in Arab countries and in India. In eastern parts of Saudi Arabia a spacing of 6.2x6.2 m is usually followed while in northern parts 7.46X7.46 m is used (Elprince et al, 1983). In Gujarat, the palms are planted 3-4 m apart (Pareek and Sodagar, 1986).
Irrigation
The date palm is drought resistant and is able to survive for long periods without irrigation. Drought, however, retards the growth. If available, date palm uses water lavishly. It is highly tolerant to excessive Irrigation and floods but permanent water logging is injurious. To maintain maximum growth, the root zone up to 2-3 m should be kept moist and not allowed to dry.
Immediately after planting, light and frequent irrigation must be given. Mulching may be useful at this stage. In sandy soils, irrigation may have to be given every day or on alternate days. The frequency of irrigation is reduced after the offshoots have established which will depend upon soil texture and weather conditions. In California, bearing gardens are usually irrigated every 7-14 days during mid-summer and every 20-30 days during winter (Nixon, 1969). In a dry soil, 2-3 irrigations totaling 8-12 acre inches in rapid succession should be given and thereafter 4-6 acre inches per irrigation be sufficient.It has been estimated that 4-5 acre feet of water is required to grow palms where the soil is dry during ripening and 6-8 acre feet will be required where heavy irrigations are continued throughout the year (Tate and Hilgeman, 1962). Experience in Coachella Valley indicated that on light soils not less than 9-12 acre feet of water per year is necessary for palms in full production and that from 12-18 acre inches per month is required during the summer (Nixon, 1969).
Irrigation trials conducted in Central Iraq revealed that irrigation water accounted for 12,000 m3 of a total water consumption of 18,000 m water per hectare per
year in cultivars Barhee, Braim, Maktoom and Sayer. These were provided by
10 irrigations fortnightly in June, July and August, monthly during May, September and October and once during November to April (Abou Khaled et al., 1981).
Hussein and Hussein (1983a) in Egypt, with cv. Sakkoti found that leaf growth,
leaf size, and fruit fresh weight, moisture content and TSS contents were increased
with increasing irrigation. Total sugar concentration and sucrose were significantly
higher with no irrigation than in the maximum irrigation treatment (24 application annually). Reducing sugar percentage, however, followed the opposite trends.
Heavy irrigation increased mean yield/palm but produced fruit of high moisture
content and thus delayed maturity. Irrigation based on 12 applications per year 4 of 300 m3/feddan (=1-038 acres) at interval of about 4 weeks was considered best.
Water is usually applied in furrows or in basins. Trickle irrigation was found j to give significantly higher yield than sprinkler irrigation (Reuveni, 1972).
Date palm is highly tolerant to saline irrigation water, but under such conditions its growth is retarded. In Saudi Arabia, date gardens have been irrigated with artesian water of 2.000-2,500 ppm salt for several years with satisfactory results In such conditions, over a number of years, drainage become a problem and therefore, irrigation water should also account for leaching requirement. At Al Hassa it has been possible to irrigate date palms with water of salinity up to 3-5 mmhos/cm (about 2,240 ppm) if a leaching requirement of 7 per cent was provided for. With irrigation water of 5-3 mmhos/cm salt content and leaching requirement of 1] per I cent, yield reduction was only 10 per cent. Furr and Ream (1968) found that the growth of Medjool and Deglet Noor seedlings with 3,000-24,000 ppm salt (mostly chlorides) was nearly linear with increasing salinity and there was 60 per cent growth reduction with 12,000 ppm salt.
Manuring and fertilisation:
Nutrient application is largely related to its annual removal by the palms. Jacob and Coyle (1931) estimated that an acre of mature palms remove 12 kg N, 8 kg P and 20 kg K. Furr and Barber (1950) reported that full bearing date palms remove 272 kg N from an acre. El-Shurafa (1984) stated that the annual loss of dry matter through fruit harvest and leaf pruning was about 82'4 kg, including 472-4 g N,47-7gP,422-6gK,218'9gCa, 36-4 gNa, 5-8 gFe, 1-2 gMnand 1-3 gZn. Whole fruits removed the most N (272 g), P (30*8 g) and K (310-8 g) and leaf pruning the most Na(29-7g),Ca(138-7g),Fe(4-Og),Mn(0-S5g)and Zn(0-32g). In cultivar Ahmer, a dose of 600 g N, l00g P and 700g K per palm had the greatest beneficial effect on growth and productivity (Lossois, 1971). Bacha and Abo-Hassan (1983) found that addition of 1*5 kg nitrogen per palm in Khudari date palm gave the best result. Studies in the USA have shown 18 to 2-7 kg N per palm to be adequate (Nixon and Carpenter, 1978). Hussein and Hussein (1983b), however, observed that 750g N per palm per year in Sakkoti cultivar was enough for the production of good size and quality of fruits in Egypt. In Pakistan also, only nitrogen fertilization gave response.
In India, application of an annual dose of 50-60 kg farmyard manure or 1-2 kg ammonium sulphate per bearing palm in equal halves, one in January-February and the other in August-September has been recommended (Bajwa and Bakhshi, 1961). Application of organic manure has been considered important in date palm. Studies in California and Arizona indicated that 12-5 to 35'3 tonnes/ha of barnyard manure applied in late fall was adequate (Nixon. 1969).
Intercropping:
In date orchards, intercropping can be done with advantage, especially during the first few years. Pulses like lentil, gram, peas, etc., and different types of vegetables can be cultivated provided there is no shortage of water.
Leaf removal:
The bearing capacity of the palm is in proportion to the number of green leaves that it carries. Insufficient number of leaves results in low quality fruit and fewer inflorescence in the following spring, Stoler (1971) found that the number of clusters to be retained is one to every 7 or 8 leaves for cultivars Khadrawy. Zahidi, Barhee, Haiyani and Amri and one for every 8 or 9 leaves for Halawy, Deglet Noor and Dayri. Hussein et al. (1977) found 12 leaves per bunch to be the optimum leaf-bunch ratio in Barhee dates. Abdulla et a!. (1983) working on Haiyani date in Egypt found that optimum yield and good fruit quality could be obtained with 8 active leaves per bunch when 5-8 bunches were retained per palm. Tate and Hilgeman {1962) recommended that about 100 leaves per palm arc required to maintain maximum fruiting.Since about 20 leaves are produced in a year, no leaf removal is required for 5 years. The total number of functional leaves that could be maintained on Zagloul palm is around 75, while on a Haiyani palm only about 50 leaves could be maintained. Leaf pruning in June gave better results than in February, (Hassaballa et. al., 1982). Khan (1979) obtained the highest yield with 70-90 leaves per palm in Dhakki dates in Dera Ismail Khan in Pakistan.
Older leaves which are surplus than the required are pruned as they are less efficient in producing sugars. The pruning is done in June so that the bunches will be better ventilated during July and early August when most of the spoilage occurs. The spine from the leaves around the bunches are also cut during spring to facilitate pollination.
2.22 Date Palm Flower Development, Pollination, Fruit set and Fruit Thinning
Flower development:
De Mason et. al (1983) studied the floral development of date palm in California. They found that inflorescence primordia differentiate within axillary buds. The rachillae were initiated as small mounds without subtending bracts on the flattened apex of the rachies and were enclosed by the prophyll. A single bract subtends each flower primordial. Flower primordia were initiated in acropetal sequence' along the rachilate. Although mature flowers were found functionally unisexual. early development was similar in staminate and pistillate flowers. Six perianth parts were found to initiate within two alternating whorls: the sepals and the petals. Six stamens were initiated in two alternating whorls of three stamens, each, the first opposite site the sepals and the second opposite the petals.
Lastly, three separate carpels were initiated. Pistillate and staminate flowers were identical and apparently bisexual at this stage. The two flower types were found to diverge when the stamens become bilobed and elongate in the staminate but not the pistillate flowers. The pistilloids in the staminate flowers farm rudimentary stigmatic surfaces at the tip of the carpels and meristematic lumps corresponding to the position of the ovule in the normal carpels. The staminodes mature in the pistillate flowers as small triangular projections.
Pollination:
Cross-poll! Nation is the rule in date palm due to its dioecious nature. For natural pollination, equal number of male and female trees has to be grown together.4 In commercial plantation, mechanical or hand pollination is done. For this, 2-3 male! Trees are enough to pollinate 100 female palms. When the female spathes cracks open, 2-3 strands of male flowers are inserted between the strands of female flowers Thus, the flowering in polliniser palm must coincide with that in the female palm. If the male spathes open much earlier than female, the pollen is dried and stored for use at a later date.
Dried pollen containing about 10 per cent moisture can be stored satisfactorily with calcium chloride at room temperature for 2-3 weeks (Stoler, 1971). It can be stored until the next season in a refrigerator at about 4-5°C (Nixon, 1969). While Gupta and Thatai (1980) were able to store pollen at 9°C with satisfactory results, Shabana et a!. (1983) obtained best results at —13°C. Dried pollen is used either by dusting it two to three times or putting 2 or 3 cotton pieces embedded in pollen in the feamle culster. Abo-Hassan et, al. (1983) stated that fresh produced the best fruiting. Followed by that with refrigerated pollen and pollen stored at room temperature. However, khalil and Al-Shawaan (1983) found 44 to 63 fruit setting in cv. Khalas with stored pollen, compared with 43% for fresh pollen Trailor mounted palm dusters are used in the USA (Brown et al., 1969).The spathes generally emerge during February-March in north-western India and the flower opening starts during March-April. Receptivity of flower in some date cultivars decreases rapidly after spathe splitting while in others a good set can be obtained even 7-12 days afterwards (Stoler, 1971).
Similar results have been obtained in Siwi and Amhat date cultivars in Egypt (El-Ghayaty, 1983) and in Zahidi cultivar in Iraq using Ghulami, Ghannami and Ahrner pollinisers (Mohammed and Shabana, 1980). Nixon (1969) recommended that pollination should be carried out during the first 2-3 days after the spathes open. In date palm, selection of good polliniser is important because the pollen affects the size of the fruit and the time of ripening. Various manifestations of metaxenia have been reported by Stoler (1971). The pollination of Deglet Noor with Fard 4 pollen appreciably shortened the ripening period of fruit (Lakhowa, 1966). El-Ghayaty (1983) studied the effects of different pollinators and found that the fruits of cv. Siwi showed the highest TSS with Maghal pollen while cv. Amhat fruits had the highest TSS with Siwi pollen. Identification of good pollinisers is, therefore, of a great significance under Indian climatic conditions to advance ripening of fruits so as to avoid rain damage. Phoneix species like P. sylveslris, P. reclinala, P. rupicola, P.liourairli, P. robellini, P. padulosa, P. canariensis could also be exploited as pollenisers.
Fruit set:
Fruit set is closely related to the percentage of viable pollen and temperature conditions during pollination. In Coachella Valley, good set was obtained when daily maximum temperature was in the range of 23-9-26-7°C or higher (Brown et al., 1969). Poor set resulting from low temperature may be improved by placing paper bags over the flower clusters at the time of pollination (Stoler, 1971). A fruit set of 50-80 per cent is considered sufficient for a full crop.
Fruit thinning:
Fruit thinning is necessary to ensure adequate flowering in the following year, to improve the quality of fruit, to prevent delayed ripening and to reduce compactness of the bunches. Thinning can be done manually or by chemical sprays. Manual method is common in which removal of some bunches or removal of some strands from each bunch or shortening the length of the strands is done.The number of fruit that a paid can safely carry depends on the cultivar, age. size, and vigour of the palm and the number of green leaves on it. Under normal growth conditions, 1-2 bunches in the fourth year and 3-4 bunches in the fifth year may be left (Nixon, 1969). In India, however, as many as 8-10 bunches per palm are retained. Small, defective and broken bunches are removed in any case. Bunch removal should not be done later than 10 weeks after pollination (Miremadi, 1970)
Bunch thinning either by the removal of strands or shortening of the strands or by a combination of the two depends upon the cultivar and other conditions. The best method of thinning is by removing the inner strands of each cluster as the] outer strands have larger berries. However, generally a combination of strand removal and strand shortening is used. In long-stranded cultivars like Deglet Noor, the tips of all strands are cut to remove about one-third of flowers or fruits leaving 20-35 berries and about one-third to half of the strands are removed (leaving 30-50 strands) from the centre of the bunch (Nixon, 1969). In short stranded cultivars like Halawy and Khadrawy, cutting back tips of strands to remove about one-tenth to one-sixth of total number of flowers or fruits, and removing about half or more of the strands from the centre of the bunch are considered satisfactory. Work done in India has shown that one-third strands from the centre of the bunches should be removed (Anon., 1988).
The desirable number of fruits to be left is between 1,300 and 1,600 per palm, depending on the cultivar, (Stoler, 1971). The percentage thinning recommended is 40-50 for Khadrawy, 50-55 for Halawy, 50-60 for Zahidi and Barhee and 30 for Dayri while in Deglet Noor shortening the strands by one-thirds along with thinning of 25-30 per cent was recommended by Stoler (1971). Spraying of ethephon (100 to 400 ppm) after 10 to 30 days from fruit set was found effective in fruit thinning of cvs. Haiyany and Zagloul. The biennial bearing habit of the treated palms was found to reduce by ethephon treatment. The fruits were found to ripen earlier and had higher fruit weight and soluble sugar content due to treatment (El-Hamady et al., 1983).
2.23 Fruit Growth and Development:
Shabana et al. (I981) reported that in Sayer and Zahidi, fruit growth followed a sigmoid curve and had five stages, viz., hababouk, chimri, khalal, rutab and tamar.'-The hababouk stage starting soon after fertilization is characterized by loss of two unfertilized carpels. The chimri stage, termed as depressed period, began 4 weeks' after fruit set and lasted for 9 weeks and had two sub stages, rapid period of growth) followed by slow increase in fruit weight. The khalal stage lasted for 4-5 weeks and: had slow increase in fruit weight. During rutab stage, the fruit started losing weight,: first slowly and then rapidly for about 4 weeks, continuing for about one week in the next tamer stage. The characteristics of these stages are given in Table-4. Thus in the tamar stage, fresh weight of fruit became 9'9gand 9-1 g, respectively, in Zahidi and Sayer. Sawaya et al. (1983a) in an experiment with twenty five date cultivars in Saudi Arabia reported that the average weight of fruits at the khalal stage varied between 9-12-26-8 g and at the tamer stage between 5-92-18-26 g. Seed weight varied from 0-79-184 g to 0-62-l-25.g, respectively. Fat, N and fibre contents decreased from the khalal to the tamer stage, but the ash content was similar at both stages. Total and reducing sugars were generally higher at the tamer stage
In the Middle East, North Africa and the USA, most of the harvest is done at tamar stage when the fruit has 60 to S4 per cent sugar, depending upon location and cultivar. In India, doka or khalal fruits having about 30-35 per cent TSS are harvested since if" left on the tree, the fruits will be damaged by rains.
During ripening of reducing sugar cultivars, inversion of sucrose is rapid and apparently complete while in sucrose type dates, it is slower and is often arrested resulting in proportionately higher contents of sucrose in the ripe fruits (Rygg, 1956). Sugar accumulation continues to a significant degree even after the fruit is fully softened. The fruits have a certain amount of astringency, depending on cultivar, up [o the doka Stage which is progressively lost with the loss of color and moisture. The process of ripening is related with the enzyme activity in the fruit. In Deglet Noor dates, the onset and development of the activity of cellulase, polygalactumnase and invertase were found to be correlated with the fruit ripening (Hasegawa et a!., 1972). The fruit quality depends on the hydrolytic enzyme activity. A deficiency of invertase results in the formation of sugar-wall dates. Too low activity of enzymes causes an absence of process of cell wall degeneration and low sugar contents resulting in firm dates (Coggins and Knapp, 1969). Cellulase and polygalacturonase were absent or were at low level in the green fruit but increased during ripening which was reflected in reduction of fruit firmness in five Sudanese cultivars {Mustafa et al, 1986). The increase in proportion of soluble enzymes, however, did not appear to influence the relative amount of sucrose or reducing sugars in the ripening fruit.
2.24 Use of growth substances:
Plant growth substances have been found to influence the maturity and quality of fruit. Treatment of date fruits with 400 ppm GA increased fruit size and delayed ripening, while ethephon at 2000 ppm although decreased fruit size also hastened. Ripening and a combined treatment resulted in larger fruits which ripened early (Marel and Bondok, 1974). Treatment of unpollinated bunches with 50 ppm GA gave high percentage of seedless berries (Ketchi, 1967). One to three spraying with 2, 4-D, 2, 4, 5-TP, 2, 4. 5-T, IAA or GA3 at 25-100 ppm after flowering produced seedless dates (Abd-Alaal et al, 1983). Abd Alaal et a!. (1983) have been able to produce seedless fruits of normal size by three GA sprays, once at spa the opening and then two sprays at 4-week interval, followed by 500 ppm Ethrel spray. Similarly, Abou-Aziz et a/. (1983) also produced seedless berries by GA application at 50 or 100 ppm in Sewi dates. Application of Ethrel or pyrogallol each at 750-1500 ppm applied to Haiyani date palms 26 days before harvest hastened ripening by 9 and 6 days, respectively (El-Tanahy et a!., 1982).
2.25 Pests and Diseases:
Pests:
In India, no serious insect pest or disease confronts date cultivation. In the north-western India, insect pest like termite in young date plantation and thrips (Adihetrothrip jambudvipae), scale insects, rhinoceros beetle(Oryctes rhinoceros and Indian palm weevil Rtliynchaphonix ferrugineus) in bearing trees have been observed to cause some damage. Stored dates are attacked by cigar hoeing beetle (Lasioder ma lestaceuni).
Goniozis nephantidis should be built up in the plantation. The red palm weevil grubs enter the palm near the ground and bore into the trunk upwards. To control the weevil 5% BHC should be dusted around the trunk. Clean cultivation is also very useful. If the grubs have already entered the trunk, fumigation should be done and the holes should then be plugged. InTihama coastal plain the lesser date moth {Batrachedra amydraula) caused severe reduction in yield. Spraying of Kafil 10% EC (permetlirin) after fruit set at 3-week interval was found effective to control the pest (El-Bashir and EI-Makalesh, 1983)
Birds are a great menace when the date berries start ripening. At Jodhpur, the effective way of protection was the use of wire cages as the other type of covers built up humidity around the bunches and caused fruit spoilage.
Diseases:
The most common disease is false smut or Graphiola leaf spot caused by Graphiola phoenicus which attacks the leaves forming numerous dark brown or black pustules full of yellow spores, particularly under humid conditions. The infection causes early death of leaves. Satisfactory control of this disease is yet to be found but chemicals like 0,1 per cent Bayleton or Bavistin, 0.2 percent Fytolan and Bordeaux sprays have been found to keep the disease under check. Fruit rot caused by various fungi occur m humid weather and in poorly ventilated clusters.
