|Contents - Previous - Next|
Few plant species have developed into an agricultural crop so closely connected with human life as has the date palm. One could go as far as to say that, had the date palm not existed, the expansion of the human race into the hot and barren parts of the "old" world would have been much more restricted. The date palm not only provided a concentrated energy food, which could be easily stored and carried along on long journeys across the deserts, it also created a more amenable habitat for the people to live in by providing shade and protection from the desert winds (Fig. 1). In addition, the date palm also yielded a variety of products for use in agricultural production and for domestic utensils, and practically all parts of the palm had a useful purpose. But if the palm had an impact on human life, the influence was reciprocal, because through a long process of learning and experience, date palm cultivation was gradually adapted to man's needs. If left undisturbed, in its wild state, the date palm would, favourable growth conditions permitting, expand in an impenetrable forest of highly competitive clusters of an approximate equal number of male and female palms with relatively few reaching appreciable height or fruit producing capacity. Examples of such uninhibited growth can still be found in some of the more remote areas of the Sahara.
Thus, man learned to direct date palm productivity to his own advantage by restricting the number of plants per ha; by assisting in the pollination process, thus eliminating the need for non-productive male palms by over 95%; by propagation of the best, proven varieties by the use of offshoots, thus ensuring the continued, identical productive capacity of the mother palm. He started to care for his palm, learning the benefits of leaf and bunch management, fertilization and pest control. In this way he became assured of an annual crop of dates, leaves and fibre, because though the date crops may vary in size from year to year, they never fully fail. Through a longer cycle of replacing senile palms by young offshoots, he obtained access to palm trunks, which served in the construction of roofs, doors and utensils. Thus, with the energy and intelligence of man, and where other crops on their own would have failed, thanks to the date palm a perpetual production cycle was established, in which little was lost or accumulated. This process has existed for thousands of years, making it possible for man to live and survive in the most remote places and enabling him to cross the vast deserts.
Figure 1: (a) Rural Date Orchard (b) Note waterlifting from shallow well
However, over the last fifty to hundred years the discovery of oil, the industrialization process, improved communication systems and transport means have brought about many changes to this picture. Even the most deserted areas are now accessible by road or air, making available a great number of goods and services in direct competition with date palm products. Indeed, in many instances date palms are now only grown for the fruit they produce, with little or no use for the secondary palm products. Nevertheless, even if economic and social progress in the first instance appear to have had a negative effect on traditional date palm growing, this progress has not provoked the disappearance of the date palm. On the contrary, it has given impetus and means to find ways to adapt date cultivation and processing methods, to improve quality standards and seek new outlets for date fruit and develop products derived from dates, in order to preserve a national heritage so eminently suited for the prevailing conditions. The overall trend has been to move from mixed and random oasis date palm cultivation to organizing it as a plantation crop with similar varieties and even stands, allowing for a more efficient execution of cultural practices. This road is proving long and arduous, limiting factors being the relative shortage of high quality offshoots for new plantations, and the lack of large-scale private commercial interests, which, for instance, changed oil palm and rubber production entirely. The burden of date palm development has therefore mainly fallen on local governments. It can be said that in the total present spectre of date palm cultivation in the world, all facets of transition can be found: from the abandonment of orchards under pressure of socio-economic changes (Fig. 2), to maintaining traditional oasis date cultivation (Fig. 3); from local tenant farming, to private, mechanized orchards (Fig. 4), and large-scale privately and publicly owned plantations. This diffused picture of a crop, is also reflected in the varying successes obtained from industrialization of the date, i.e. the introduction of improved packing and processing methods. Dates considered as a fresh fruit rank number 5 in the production list of tropical and sub-tropical fruits after citrus, mangoes, bananas and pineappples. As a dried fruit dates easily top the list over raisins, figs and prunes.
The characteristics of the date palm have on several occasions clearly been described by authoritative writers (445, 363, 136, 142, 70). However, for a better understanding of the underlying reasons why certain developments have taken place, a summary is again given of the main properties, distribution and limitations of the date palm and its products.
The exact origin or gene centre of the date palm has been lost in history, but evidence of date palm cultivation goes as far back as 4000 B.C. in what is now southern Iraq. But references to date palms have also been found in Ancient Egypt, and there seems to be a consensus that the earliest form of date palm cultivation coincided with the oldest civilizations and originated in North-East Africa, stretching north east into the delta of the Euphrates and Tigris. From there date palms have spread either purposely or accidentally. Purposely, when in time of population movements the people took along their main crops. Missionaries, in the wake of the "conquistadores" introduced the date palm in some Latin American countries, perhaps more for having a supply of palm fronds for religious celebrations than for introducing a new crop. Then there have been numerous examples of accidental distribution of the date palm, facilitated by the fact that dates lend themselves perfectly to being carried along as a high calorie food, with a long-keeping quality. Soldiers on the march, traders and discoverers - all may have had their influence in spreading the date palm by leaving the seeds behind after consumption of the fruit flesh (Fig. 5).
Figure 5: Dissemination of the date palm in the Old World (363)
In more recent times there have been a number of exchanges of offshoots between date producing countries, sometimes however restricted by embargoes for protective reasons or fear of the spread of disease. The most striking example of the commercial introduction of the date palm into new lands was the importation of a large number of offshoots into Arizona and California in the U.S.A. around the turn of this century and which reached its peak in the twenties when at least 50,000 shoots had been planted forming the basis for a striving date industry, now mainly restricted to the Coachella Valley in California covering almost 2,000 ha. Ironically, this importation of offshoots has seen a period of a reverse flow, when on the wave of acquired oil revenues, several Arab countries undertook large-scale programmes to increase their date acreage but found a shortage of suitable offshoots in their own countries and resorted to foreign imports, amongst others from the U.S.
The present situation in the world as a net result of these historical developments is reflected in the map of Figure 6 (142). It shows a wide belt from the Atlantic Ocean through the Sahara, the Arabian Peninsula, into Iran and the Indus Valley in Pakistan with their main centres of production. Outside this belt the concentrations are much more localized and except for the U.S. of less importance worldwide.
In arriving at this picture of the global distribution of date production, which was to a great extent man-induced, the date palm's own limitations for productive growth must also be taken into consideration.
The often referred to statement that the date palm likes its "feet in Heaven and its head in Hell", alluding to the fact that the date palm requires an abundant water supply and high temperatures, is indicative of the basic growth requirements of the palm. When a constant natural or artificial supply of water becomes erratic palm growth soon becomes chancy as the pictures in Figure 7 demonstrate. Assuming however an adequate supply of water available for any given location, in the first instance, the temperature therefore becomes the determining factor. Within the climatological limits of where the palms are now grown, i.e. the hottest part of the Sahara, the upper range of temperature tolerance is of little importance to the palm. Maximum temperatures of around 50oC as they occur do not harm the palm, though they may influence the physiological aspects of the fruit they bear, which usually become hard and dry in these circumstances. Resistance to these high temperatures must be attributed to the fact that firstly the date palm, compared to most other plants, has only one growing point, on top sof the trunk well enshrouded in the bases of older fronds made of highly insulating material. By the time the new fronds and fruit and flower bunches, sprouting from this growing point, have to face the sun, they are already tough enough to withstand the heat. Inspite of this insulation, the growing point would eventually heat up if no cooling effect existed simultaneously. This is provided by the subsoil water supply which slowly rises in the trunk and evaporates through the leaves. Both effects result in a diurnal temperature amplitude of not more than 4 to 5° C (363) in the growing point whilst ambient temperatures may have a range, especially in desert regions, of 20° C and more. This dampening effect of daily temperature variations makes it possible for the palm to survive, not only from extreme high temperatures but also, although to a lesser extent, from lower or temperatures. Damage from cold is shown as the drying out of foliage to death of the palm in severe cases. No exact temperature range is known, because factors like the length of exposure (expressed in hours per day and days per month) and the varietal characteristics and age of the palm also play a role. An idea of the extent of tolerance to cold is therefore based on isolated observations such as: at -15° C drying out of foliage occurred but palms survived (363); in California damage was never observed when the temperature remained over -7° C (391).
There are many more of these types of observations for different locations, but for the sake of "order of magnitude" it can be said that palms can resist moderate freezing temperatures and that damage can be expected below -6 to -7° C. A secondary effect of a submission to cold, without damage to the palm, is delayed flowering (363).
It can therefore be concluded that the date palm can survive in a wide temperature range (up to about 50-60° C). But to complete a full productive cycle, i.e. to bear fruit, the date palm requires a certain amount of heat energy. To establish the approximate amount of this energy has been of concern to date researchers as early as the last century, the reason being to create a tool with which to predict suitability of new lands for date cultivation based on meteorological records.
Accepted and confirmed data related to temperature requirements are that: the date palm will flower only when the shade temperature rises over 18° C; will fruit at temperatures above 25° C and vegetative growth will stop under 10° C (100). To quantify the minimum total amount of heat required for a full productive cycle the system of accumulated heat units was adopted, which, as a start, was the sum of the daily average temperatures in the period from flowering to fruit ripening. A first figure obtained was 5100° C (100). Later researchers have attempted to perfect the method by not taking the daily mean but the daily maxi-mum temperatures into account or by taking 18° C (below which no flowering takes place) as the zero point instead of 0° C or 10° C. Uniformity of the start and the end of the count of total heat units has also been lacking (examples: from flowering to maturation of the fruit; from minimum 18° C at the beginning to maximum 18° C at the end of the season; from 1 December to 30 September of the following year). Adding to this that some researchers like to express themselves in 0F and others in °C.
All these variations in determining the limit of required heat units below which commercial date cultivation is less likely to be successful, have made the results difficult to compare. In evaluating them one needs the exact specification of the measurements made. Perhaps the most realistic and useful method is to apply the sum of the mean daily temperatures minus 18° C, accumulated from pollination to harvest. Under these criteria for North Africa 1800° C is considered the minimum required for the so-called "common varieties" and 1890° for the Deglet Nuur variety (142).
Inspite of some of the inconveniences created by the diversication of the measuring methods (some of which can be remedied by recalculation) the summation of heat units has been a useful tool in guiding the horticulturist in his decision making for the suitability of commercial date production in new lands. Not only in the early days of this century (561, 317), but also in more recent times in countries such as Kenya and Botswana, the method has been applied (547, 546). It is to be understood, however, that a satisfactory number of heat units alone is not a panacea to predict the success of date production.
Temperature being the most vital factor and assuming a sufficient water supply, and an allowance for varietal tolerance and isolated favourable microclimates, the possibility for reproductive date palm growth becomes therefore largely a matter of latitude and altitude. But there are other climatological factors, that, at least in the eyes of man, affect date production qualitatively and quantitatively. They are humidity of the air, rainfall and wind.
Rainfall during and right after pollination may reduce the fruit setting but is not generally a great preoccupation. More feared are the (early) rains during final maturation of the crop, a realistic possibility in many date growing areas.
Apart from direct physical damage, the secondary effects of increased humidity and lower temperature work against the final maturation of the crop and favour insect infestation and fungal growth. It is for this reason that in several areas preventive measures are taken by protecting the fruit bunches with covers (Fig. 8).
Bunch covering is, however, not only practised against rain damage but traditionally is also used in the form of coarsely woven well-ventilated baskets (sund) to protect the maturing fruit from birds and prevent early ripening fruit from falling to the ground. At harvesting time the baskets are carefully lowered to the ground on a rope (Fig. 9). When protection against early rain or sunburn are the prime objectives, increasing temperatures (which may reach 65oC under the paper cover with an ambient temperature of 40oC) may benefit maturation, but also create a favourable environment for fungal growth and spoilage in general. Material choice of the cover and ventilation therefore become of prime importance when resorting to this method of bunch protection.
Humidity of the air, expressed preferably as a relative percentage (i.e. %-age of saturation at prevailing temperature), because it is a measure of the absorptive moisture capacity of the air, is of great importance to the type and quality of the final product. The relation is rather simple: in regions with low relative humidities such as the internal desert areas, dates tend to dry out on the palm until they are hard with a moisture content as low as 10% (Fig. 10). This may be advantageous for increased keeping quality and food to weight ratio, it is less attractive, generally speaking, to the consumer. On the other hand, high relative humidities, such as frequently occur in coastal areas, delay the evaporation of moisture to the extent that the dates do not reach the "safe" moisture content for preservation and have to be harvested at a perishable stage, to be either consumed within a matter of days or to be preserved by artificial means. For instance, the major part of the date crop in the Nile Delta in Egypt is consumed at the "fresh" stage.
Some figures to illustrate this situation are given in Table 1(363, 142):
Average relative humidity levels in different locations (%-age)
|South Algeria, Touggourt||43.5%|
|Interior Tunisia, Tozeur||61%|
|Coastal Tunisia, Gabès||66%|
|Nile Delta, Egypt||68-74%|
These figures correspond very well with the type of date prevalent in the areas under consideration.
The third climatological factor which has an impact on the final fruit quality is wind, which, since pollination is done by hand, has only negative, though not severe, effects on date production. The palm itself can withstand gale force winds, though these may result in damage to pending fruit from hitting against the fronds. Sand-laden winds like the Khamsin of Egypt, the Ghibli of Libya and the Sirocco in Tunisia and Algeria, are likely to deposit dust on the surface of the fruit especially when it is sticky. This problem is aggravated when dealing with varieties of which the skin tends to loosen during ripening and the dust will settle on the date flesh, with no possibility of it being washed out completely.
To complete the description of the main ecological requirements, the variations of which may affect the productive capacity of the palm and quality of the fruit, a few remarks on water and soil requirements are made.
Unless special provisions are made to accumulate and divert the surface water, rainfall has little importance in supplying the palm with its daily water requirements. In the majority of cases the cultivated date palm, therefore, has to be irrigated, either from rivers, streams, or wells. In a few places this can be arranged by harnessing natural forces such as gravity when rivers originate uphill and their waters can be diverted into the date gardens, by artesian wells, or by tidal irrigation, which is the classical case in the Shatt-el-Arab region (Fig. 11). Otherwise water has to be lifted either by man (Fig. 1b), animal or pump. Total annual requirements per palm have been estimated on many occasions (summarized in 363 and 142), which show a certain divergence, no doubt caused by different soil and climatological conditions. Nevertheless as an overall average for programming purposes a through-the-year figure of 0.5 l/palm/minute would seem adequate. This would correspond with roughly 250 m3/palm/year. If one considers that the water lifting capacity of one ox (and man) from 20 m deep is about 2 m3/hr (363), it shows clearly how much time and effort was going into supplying water to the palms. Another indicative figure is that about 2 m3 water per kg of fruit is used in the best of circumstances. It therefore shows that the date palm, inspite of its connotations with hot and dry climates, is a more than average consumer of water, but it compensates for this by tolerating relatively high salt contents compared to other crops. This fortunate circumstance gives it access to water supplies otherwise of little use in agriculture. Bearing in mind that very good drinking water contains 100 ppm (parts per million) of salts, normal "mineral" water around 600 ppm, the limit for use as drinking water is around 1500-3000 ppm and seawater goes as high as 40,000 ppm, the figures given in literature show the following tolerancy levels for the date palm: in the Algerian Sahara (Baskra, Touggourt) salt contents vary from 2000 to 5000 ppm; in Egypt studies showed that maximum salt content of irrigation water should not exceed 2000 ppm (363); experiments on young seedling palms showed a linear decline in growth rate from the level of 3000 ppm salts in the water supplies (166). Examples are also given of tolerancy figures going as high as 6000 and 7000 ppm but at these levels an adverse effect on crop yield and quality can certainly be expected. A visible example of the relative salt tolerance is the northwards ongoing process of decreasing date yields on Abadan island (Shatt-al Arab region) in consequence of the increasing salinity of the tidal water with which the date gardens are irrigated, and which in turn is the result of the more intensive use of the river waters (Euphrates, Tigris, Karoon, Dez, Karchech) feeding the estuary in which Abadan island is located (309). Compared to other fruit crops the date palm is, however, considered to have a high tolerance for salts compared to other fruit crops as the following table shows (456).
Relative salt tolerance of fruit crops
|High salt tolerance
(ECe x 10³ = 18*)
|Medium salt tolerance
(ECe x 10³ = 10)
|Low salt tolerance
(ECe x 10³ = 5)
|Date Palm||Pomergranate||Pear Almond|
*The numbers following ECe x 103 are the electrical conductivity values of the sat-uration extracts in millimhos per cm at 25° C associated with a 50% decrease in yield.
Apart from having a certain drought resistance because of its relatively few and well protected foliage, the date palm can withstand flooding for prolonged periods partly explained by the presence of numerous and large air spaces in its root tissue (136).
With regard to soil requirements the date palm is not very demanding and will grow on almost any type of soil, from almost pure sand to heavy alluvial soils, provided they furnish the basic needs of anchorage to the palm, minerals, water penetration and drainage. The optimal situation lies, therefore, in the middle, and deep sandy loams are often quoted as the more suitable type of soil for the date palm.
In conclusion of these general ecological characteristics for date palm cultivation reference is made again to the map of the distribution of date palms in the world (Fig. 6) and the actual date production figures in the different countries in Appendix I as derived from the FAO Production and Trade Yearbooks (155).
The more important date producing countries are shown below in order of the size of the crop:
Date Production ('000 MT)
Sub-total 6 major producers 2637
Sub-total medium producers 402
The remainder of 372 000 tons is produced in some 22 countries of which the more important are Morocco, Chad, USA, Israel, United Arab Emirates and Yemen 372
World 1839 2208 2645 3411
From these figures it can be concluded that date production worldwide has been steadily increasing over the last 30 years and in 1990 reached 3,400,000 tons, 85% more than in 1960. Over 75% of this tonnage is produced in six major date producing countries, 90% of total world production comes from 10 countries out of a total of 32 date producing countries. This is as far as quantities is concerned: a qualitative evaluation is complex because of the large varietal nuances and differences in the production areas. Suffice to say that there is a great quality factor involved in estimating the crop value and that some of the smaller producer countries produce some of the best quality fruits in the world trade market.
The date palm (Phoenix Dactylifera) is a monocotyledon of the family of the Palmae, one of the genera of which are the Coryphoideae, of which one species is Phoenix Dactylifera. It is a feather palm, characterized by compound leaves with a series of leaflets on each side of a common petiole, originating from one growing point on top of the trunk. Two close relatives of the date palm are the Wild Date Palm (Phoenix Sylvestris), widely used in parts of India for sugarmaking (jaggery), and the Canary Palm (Phoenix Canariensis) frequently found as an ornamental palm on Mediterranean coasts and the Americas (Fig. 12), on occasion interrupted by a lonely, and unproductive, true date palm (Fig. 13).
The date palm may reach an age of over 100 years and reach up to 24 m in height to the growing point. Normally the useful age limit is less and consequently the height will not be more than 15-20 m maximum before it will be cut down because of declining yield and increasing difficulty (and danger) to reach the crown during pollination, bunch management and harvesting (510). A schematic picture of the date palm during a one-year productive cycle is given in Figure 14.
Five main stages in the palm's life cycle can be distinguished (322): 1. growth of the offshoot attached to the mother palm (5-8 years); 2. growth of the separated and transplanted offshoot (4-6 years); 3. start and increasing fruit yields and formation of offshoots (14-20 years); 4. full productivity but no more offshoot formation (30-35 years); 5. declining yields.
Leaves are formed in buds in a slightly ascending spiral around the growing point, at the rate of 10-30 per year. With an average lifespan of 3-7 years the number of leaves per palm varies from 30-140. Initially, the young leaf is enclosed in a leaf sheath of tender tissue which at a length of about 20 cm will open to give passage to the extruding leaf. The sheath tissue will dry out and eventually only the fibrous tissue, known as palm fibre will remain at the base of the leaf. Leaves may reach a length of 6 m, with an average of 4 m (142). Under natural conditions, the leaves, after their useful life is over, will dry and bend down alongside the trunk where they would stay for quite a while before dropping to the ground. The date cultivator, however, will each year remove the old leaves in order to give him better access to the crown. The leafbase will remain attached to the trunk and where palms are still climbed, are used as steps for the climber's feet.
The leaflets (pinnae) of the compound leaf (frond) (Fig. 15a) may range in length from 15 cm to about 1 m with a width ranging from 1 to 6.5 cm. Total number of leaflets on one frond may vary from 120 to 240. Apart from pinnae the petiole (midrib) usually also grows spines in the lower region. They are hard and very sharp pins, ranging in length from almost nothing to over 20 cm. They are situated at the two outer edges of the midrib and may number from 10 to about 60. The date cultivator will quite often remove the spines to prevent injury during cultural practices.
Figure 15: Major Parts of the Date Palm
Some 12 (0-25 range) flower buds develop during the winter in the axils of some of the leaves just below the growing point. The inflorescence, enveloped in a sheath or spathe (Fig. 15b), pushes through the fibre on the leaf base it originated from to a length of 25 to 100 cm. It will split open upon maturation of the inside flower cluster, which consists of a main stem (fruit stalk) which rapidly lengthens outside the spathe, and a number of spikelets originating mainly from or near the apex of the main fruit stalk.
The date palm is dioecious, which means there are male and female plants. The yellowish flowers are small, attached directly to the spikelets; male flowers are sweet-scented and have six stamens, female flowers consist of three carpels with ovules, of which normally only one will develop into a fruit (Fig. 15c). For fruit setting, fertilisation of the female flowers by male pollen is required, which in date palm cultivation is not left to the wind or insects but is done traditionally by man by inserting a piece of a spikelet of male flower at the moment of the opening of the female flowers. More modern methods will collect the pollen from the males and in combination with a carrier (such as flour) will be dusted on the female flowers with a mechanical device.
Upon successful pollination the fruit will now start to develop through different distinguishable stages until it reaches maturity, a term which, especially in date cultivation, needs qualification (see later).
As not all female flowers are produced at the same time, the stage of maturity of the dates is also staggered for the different bunches. Even on one particular bunch, ripening will usually start from the lower end of the hanging bunch going upward. This means the grower will be required to climb his palms more than once for each operation, e.g. at least 3 times for pollination. At the last round of harvesting the fruit bunch is cut off.
It is difficult to give an average figure for the size of the annual crop per palm because it depends so much on growing conditions, the variety, the age of the palm, and the skill of the cultivator. In comparing crop yields an allowance must also be made for the stage at which the fruit is harvested, for instance fresh hard dates (Khalaal or Bisr, around 50% moisture) yield much more in fruit weight than a dry desert date (say 15% moisture).
A unique record was kept by a private Californian date grower (91) who, over a period of more than twenty years (1934-1956), kept track of all fruit bunches formed and the total weight of dates produced from the time of planting the offshoots for a total of 435 Deglet Noor Palms. The following cumulative figures give an interesting picture of the production capacity of a commercial date grove under Californian conditions (Fig. 16):
Production record of a Californian Date Grower
over 21 productive
|Number of palms||435||435|
|Number of bunches||114 214||68 295|
|Dates produced (kgs)||864 162||532 993|
|Average date weight/ bunch (kgs)||7.56||7.80|
|Average number of bunches/tree||262.5||157.0|
|Bunches per tree (1 yr. av.)||12.5||15.7|
|Kgs per tree||1985.9||1225.3|
|Kgs per tree (1 yr. av.)||94.6||122.5|
Additional observations during this period were the following:
i. formation of offshoots (up to 8 per tree) does not seem to have an effect on the productive capacity of the palm compared to palms not forming offshoots
ii. full maturity of the palms is not reached before 12-13 years
iii. outside rows of palms, exposed to more sunshine bear consistently more fruit than those planted inside, giving some weight to the thesis that the standard planting distance of 30 x 30 feet (9 x 9 m) may be a little too close (from a productivity point of view).
The above production figures from an intensive date cultivation system go far beyond the results of traditional date growing practices. Overall country averages in the date production countries do not go much higher than 20-30 kgs/palm/year, though the production inputs are also less (fertilizers, pesticides) and generally the palms are much closer spaced. Even so, in well organized date plantations in favourable environments in the old world yields may reach 100 kgs/palm/year and over (Fig. 17).
Figure 17: Harvesting Whole Bunches of Khalaal (cv Khuneizi). Note strung (nylon) rope attached to climbing belt to slide down the bunch (Bahrain)
Annual crop volume and individual fruit size can be influenced by the grower by bunch removal and fruit thinning. Bunch removal, usually the very early and late ones, is aimed at avoiding overbearing of the palm with a consequent poor yield in the next year. For mature Deglet Noor palms normally not more than 15 bunches are left on with an overall leaf to bunch ratio of 8 or 9. Fruit thinning is accomplished in three ways:
i. cutting back the tips of the strands by about ¼ along a horizontal plane
ii. removal of the inner strands, leaving about 40-45 strands per bunch
iii.reduce number of dates on one strand to about 40.
The result of fruit thinning is less overall yield but bigger sized fruit developed on well ventilated bunches (Fig. 18).
Figure 18: Bunch of Thyinned Deglet Noor (California)
Both bunch removal and fruit thinning are location and variety specific, not necessarily transferable elsewhere without on-site testing.
The trunk of the palm is composed of vascular bundles held together with connective tissue. Towards the periphery, where the leaf bases are embedded, the tissues tend to become more lignified and tough. The diameter of the trunk will not increase once the full crown of fronds has developed.
Roots of the date palm originate from the more or less ball shaped foot of the trunk and are singular with little or no secondary thickening or branching into rootlets. The date palm has no tap root, but 4 zones in the root system can be distinguished (363).
1st Zone: Roots sprouting from the upper part of the trunk base. They have partially a negative geotropism and do not go deeper than 1/4 m, apparently playing a role in the respiratory system, evidenced by the large air pockets in the tissue.
2nd Zone: This is the most intense rooting zone with numerous roots branched into rootlets spreading into the earth with the main purpose of collecting nutritive substances and moisture. By and large the zone stretches from a little below to 1 m below ground level.
3rd Zone: The development of roots into the third zone (roughly from 1-2 m underground) largely depends on the availability of nutritional substances in the higher zones, i.e. in poor soils the roots of the second zone will also extend into the third zone.
4th Zone: Finally in the 4th zone, some 2 m below ground level, roots may develop with a strong geotropism, in search for water, when this is not available in sufficient quantities in the higher zones.
In its natural state the date palm would propagate by seed, which either falls to the ground after the fruit has matured or after having been spread byanimals or man carrying away and eating the fruit. The date palm, however, also has the capability of vegetative propagation by the formation of offshoots (Fig. 19 and 20). Although in the natural state these offshoots tend to become competitor to the mother palm, for man this method of propagation has two major advantages: firstly, the offshoot is the exact replica of the mother palm, thus the established characteristics of the palm are carried on unchanged. This in contrast by multiplication through seed, which includes always the genetic inheritance of the father palm and carries no guarantee of continued desirable qualities in the offspring. This becomes of special importance when one considers that it may take up to ten years before the first fruits are produced on a seedling palm. This is in contrast to fruit from vegetative offshoots which may bear fruit after 4 to 5 years. Though selection programmes through cross pollination have been initiated the results, because of the time factor and the low expectancy rate, have not been encouraging. Almost all propagation nowadays is done through offshoots, though it has its limitations when rapid expansion of date cultivation of one particular variety is desired, the reason being the slow vegetative reproduction rate. One mother palm will produce 6 to 12 offshoots in her lifetime, or at the very best an average of one child every five years, which does not allow for vast replacement or expansion programmes. Much attention is therefore given with high expect-ations focussed on propagation through tissue culture. Results at the laboratory stage have been positive and promising but turning them into practical field applications has so far not become foolproof.
Figure 19: Newly Planted Offshoots (8 x 16 m) (Bahrain)
Figure 20: 4-Year Old Plantation of Zahdi Offshoots (California)
With the above general description of world date production and the major characteristics of date palm cultivation the following chapters will focus on the products derived from the date palm.
The more important product is the date fruit, in particular in a market economy. In a subsistence economy, however, the situation is more diffuse with respect to the use of other palm products, especially in the more remote areas.
Because of the great diversity in date fruits, originating not only from inherent varietal differences, but also from different growth conditions and post-harvest treatment, the description of the use of dates has been classified into four groups, i.e. I whole dates, II date fruit products and preparations, III derived date fruit products and IV by-products of date packing and processing. In Chapter V the remaining palm products will be reviewed.
|Contents - Previous - Next|