The term date (Khorma) has a Persian root which has been loaned to other languages such as Indian, Urdu, Turkish, Indonesian, and Malaysian.
Palm date, monocotyledon and indigenous to tropical regions, has huge leaves and is categorized as palm trees. Date belongs to the family of berry whose entire fleshy part is edible and nutritious. It has been an integral part of human’s diet since ancient times. Its edible fruit has a hard seed, a thin skin, and a sweet taste which hangs on a palm in the form of a cluster. The height of the palm is 10 to 20 meters or more some times.
The unripe date is called “KHARAK” or “KONG”. In Arabic language, however, the unripe date is called “HABABOOK”. “ROTAB” is another name associated with non-fully ripe dates which have a moist texture and contain less sugar compared with fully ripe ones.
The date palm grows in tropical and semi-tropical regions such as Iran. Although it is believed to have been originated from Mesopotamia, Saudi Arabia, and northern Africa, the scientific studies reveal that the date palm is a member of a species called” P.H. SIVESTRIS” which is indigenous to India. Archaeologists are of the opinion that palm-tree gardens were created 5,000 years ago. Date palms have been planted in Iran since ancient times and before Achaemenid dynasty. This tree has been referred to in SASANIAN literature, i.e. the book “BANDHASHAN”. In Chinese reference books, the country of Iran or as pronounced in Chinese language “Bousi” is known as the land of date palm— called Persian jujube and 1,000-year-old jujube in their language. In the late 9th century, the date palm was taken to China from Iran and was planted there. Amongst European countries, Spain has a longer history in growing date palms.
Classification of date by type:
Dried Date: a ripe date which moisture rate below 15%
Semi Dried Date: a ripe date with the moisture rate between 15% and 18%
Fresh Date: a ripe date with the moisture rate between 18% and 35%
Location of dates in Iran:
In recent years Iran is one of the leading Countries in Date production in the world, with annual production of about 900000 metric tons.
According to the Ministry of Agriculture, there are more than 400 species of date all over Iran but just a few of them have commercial value. Generally dates according to their level of moisture categorized into three big groups which are: Dry, Semi Dry and Wet.
Each part of Iran has a suitable climate for producing special sort of dates. Kerman province is the center for three sorts of dates which are Mazafati, Klute and Farehkon. Other provinces like Hormozgan, Khuzestan and Bushehr are suitable for other sorts like Piarom, Sayer, Kabkab and Zahedi. The main areas that produce dates in Iran are Hormozgan 21.6%, Kerman 21.1%, Khusistan 17.6%, Bushehr 13.4%, Beluchestan 12.2%, and Fars 12.3%.
Sayer Dates come from Shadegan which is located in the southwest of Iran. It has 90 km distance from Ahvaz and 971 km from Tehran. People from Shadegan mostly speak Arabic and well-known for being interested in poetry. The main source of income for local people is agricultural products and most people are involved in producing dates. Sayer date is the most common kind of date that local growers bring up. There are 2,000,000 dates tree in Shadegan which produce more than 50,000 Tones dates annually. The two big rivers that flow in this area are Karun and Jarahi and growers mostly use water from Jarahi. They made some dams on the river and use its water for irrigation.
Piarom dates belong to semi-dried group of dates and because of its shape and taste, it is known as "chocolate dates" in the international markets. Piarom is the most expensive and luxury dates in the world.
Piarom has a very thin and inseparable skin, which gives the capability of complete washing. Origin of Piarom is Haji Abad, located in the north of Hormozgan province. Due to dry and hot weather of this area, it prepared a suitable condition for growing this kind of dates. According to authorities, there are around 4,000 hectares of different kinds of date garden in Haji Abad which around half of them (2000 hectares) used to produce Piarom. Total production from gardens in this area is more than 10,000 tons each year which mostly export to European markets.
Mazafati (Ruttab) is one of the best products that are produced in warm and dry regions of Iran. This type of date is indigenous to BAM in KERMAN-Iran.
Variety and high quality, as well as the reasonable price of Iran, has caused various kinds of raw materials produced in Iran to be popular in the world and to increase the export value of this high-quality date palm.
In Iran, more than 100 different types of this product are produced, some of which are very popular and in many Asian and European countries, there are many fans and buyers.
This date might be considered as one of the most palatable and delicious dates worldwide particularly since it is eaten in its mid-stage of growth (ROTAB). Almost anyone finds this date tasty. Having a flattering black color, this type of date has a moistness ranging from %15 to %35 according to the harvest time and the cultivation place. The seed size ranges from 5.2 to 4.5 centimeters.
Growth and development stages of date palm fruit
The growth and development of date palm fruit involve several external and internal changes. These changes are often classified on the basis of change in color and chemical composition of the fruit, as five (5) distinct stages of fruit development, known as Hababouk, Kimri, Khalal, Rutab and Tamar.
These terms are Arabic and there are no equivalent English words.
a) HABABOUK STAGE
Starts soon after fertilization and continues until the beginning of the Kimri stage. It usually takes four to five weeks to complete and is characterized by the loss of two unfertilized carpels; a very slow growth rate is another characteristic. Fruit at this stage is immature and is completely covered by the calyx and only the sharp end of the ovary is visible. Its average weight is one gram and the size is about that of a pea.
b) KIMRI STAGE
Local call this step Chogholi. At this stage the fruit is quite hard, the color is apple green and it is not suitable for eating. This stage lasts from a small green berry to an almost full-sized green date. It is the longest stage of growth and development of dates and lasts a total of nine to fourteen weeks, depending on varieties.
During the first 4 to 5 weeks, there is an average relative weekly growth of 90 %, while during the second period of Kimri stage there is only about 22 % growth.
The first phase is characterized by a rapid increase in weight and volume, rapid accumulation of reducing sugars, low but increasing rate of accumulation of total sugars and total solids, highest active acidity, high moisture content though slightly less than that of the second phase.
c) KHALAL STAGE
In local, they call it Kharal. The fruit is physiologically mature, hard ripe and the color changes completely from green to greenish yellow, yellow, pink, red or scarlet depending on the variety. It lasts three to five weeks depending on varieties, with a low average relative weekly increase in fruit weight (3 to 4 %). At the end of this stage, date fruit reaches its maximum weight and size, but sugar concentration (saccharose), total sugar and active acidity have a rapid increase associated with a decrease in water content (around 50-85 % moisture content). It is to be noted that date fruit accumulates most of their sugar, both the sucrose type and the reducing sugar type, as sucrose during the Khalal stage. At this stage color of the seed changes at the end from white to brown.
However, Khalal dates must be eaten immediately after harvesting as they will keep for only a few days without cold storage (7°C for one week or 0-1 °C for longer periods) due to their high sugar and water content which cause fermentation during hot weather. If supply and demand are in equilibrium, the Khalal season will last for a couple of weeks.
Varieties harvested and marketed at Khalal stage present the following advantages: minimum infestation, a possibility of cutting the whole bunch, easy handling and packing, high yield and consequently high income.
d) RUTAB STAGE
Also called soft ripe stage. At this stage the tip at the apex starts ripening, changes in color to brown or black and becomes soft. It begins to lose its astringency and starts acquiring a darker and less attractive color from the previous stage. At this stage, which in total lasts for 2 to 4 weeks, there is a continuous decrease in fresh fruit weight mainly due to loss of moisture. The average weekly decrease in fresh fruit weight is 10 % during the last week of the Rutab stage.
An increase in reducing sugar, a rapidly increasing rate of conversion of sucrose, a gain of total sugars and total solids also characterize this stage. It has already been observed in respect of the reducing sugar type date, i.e. With softening, the last of the tannin under the skin is precipitated in an insoluble form, so that the fruit loses any astringency that may have remained in the Khalal stage from the Kimri stage.
It is a very good stage for consumption as a hard ripe date. With the exception of a few varieties, fruit at this stage is very sweet. It is, however, very important to harvest and market the fruit at this stage. Unless they are cold stored, the fruits quickly turn sour and become of no commercial value. For dessert purposes, most people prefer dates after they have passed the Rutab stage.
e) TAMAR STAGE
Synonyms: Tamer, Tamr, also called full ripe stage or final stage in the ripening. This is the stage when the dates are fully ripe, and they completely change the color from yellow to dull brown or almost black. The texture of the flesh is soft. The skin in most varieties adheres to the flesh, and wrinkles as the flesh shrinks. The color of the skin and of the underlying flesh darkens with time.
At this stage, the date contains the maximum total solids and has lost most of its water to such an extent (below 25 % down to 10 % and less) that it makes the sugar water proportion sufficiently high to prevent fermentation. This is the best condition for storage. The average relative decrease in fruit weight during this stage is 35 %. The loss in fruit weight continues if fruits are left on the palm. This stage is equivalent to that of the raisin in the grape and the dried prune in the prune type of plum. At the Tamar stage, the fruits on a bunch do not all ripen simultaneously, but over almost a month. Hence, three to four harvest times are necessary.
Dates in all the above stages except the Tamar are perishable, due to their high water content.
Whole dates are harvested and marketed at three stages of their development (Khalal, Rutab and Tamar) depending on variety, climatic conditions and market demand.
Temperature, rain, humidity and wind are the most important climatic factors which determine the suitability of a specific site for growing date palm.
The highest maximum temperatures found in the date growing areas of the world are the result of low humidity, great insolation and long days in summer.
Date palm is cultivated in arid and semi-arid regions which are characterized by long and hot summers, no (or at most low) rainfall, and very low relative humidity level during the ripening period. Exceptional high temperatures (± 56°C) are well endured by a date palm for several days under irrigation. During winters, temperatures below 0°C are also endured. The zero vegetation point of a date palm is 7°C, above this level growth is active and reaches its optimum at about 32°C; the growth will continue at a stable rate until the temperature reaches 38°C/40°C when it will start decreasing.
Even though date palm is a thermopile species, it withstands large temperature fluctuations. Below 7°C growth stops and this stage is called a resting period. When frost periods are suspected, inflorescence should be protected with craft paper bags immediately after pollination. From -9 to -15°C, leaves of medium and outside canopy will be damaged and dry out. If these low temperatures are maintained for a long period (12 hours to 5 days) all leaves will show frost damage and the palm will look as if it was burnt (cases of Morocco date plantations in 1952, and 1965; Iran, 1964; USA, 1913, 1937, 1949 and 1959). The more leaves damaged, the greater the possibilities of poor fruit quality that year. Poor flowering could also be expected.
After frost occurrence and during early spring, the damaged palm restarts its normal growth.
Date gardens that were irrigated during frost periods were less damaged than the ones that were not irrigated.
The Zahidi variety (Iran) was found to be the least damaged by frost while Khalas (also Iran) is the most sensitive.
Date palm culture has mostly been developed in areas with winter rainfall which does not cause harm to the date fruits, but benefits the soils of the plantations by lessivating the deposited surface salt and avoiding the upward movement of salt from lower layers. Harvest begins mid-August until the end of October. Rain during the flowering and harvest season is likely to cause some damage to the fruits.
Air relative humidity
Depending on air humidity at the locality of a date palm plantation, various advantages and/or disadvantages are found. In fact, the date palm eco-system is mostly of an arid nature where air relative humidity has a large influence.
In the presence of high air humidity, some leaf diseases, such as Graphiola leaf spot (Graphiola phoenicis Moug. Poit.), are becoming more prevalent, while others, such as the Date mite (Bou-Faroua), become rare or absent. On the other hand, when air humidity is low, fungal diseases are absent, while pest and mite attacks are dominant.
Air humidity also affects the date quality during the maturation process. At high humidity, fruits become soft and sticky, while at low humidity they become very dry.
When air humidity is high during maturation, the skin of the date fruit shows several cuts or breaks with an edge-blackening (Blacknose), the soft fruits fall to the ground and consequently lose their commercial value.The above effect occurs only when high humidity is experienced immediately before the Khalal stage. After the fruit acquires the Khalal colour, checking no longer occurs. After the flesh softens in the Rutab stage, the skin does not break readily upon contact with moisture, but the fruit absorbs moisture and tends to become sticky and more difficult to handle. After the Tamar stage is reached, air humidity causes little damage to the fruit unless it is neglected.
Compared to other plant species, the date palm shows no damage under windy conditions. In fact, date palm can withstand strong, hot and dusty summer wind and consequently protects the other cultures by breaking the force of the wind and sheltering more susceptible vegetation.
Wind is, however, a carrier of dust and sand that adheres to the date fruits in their soft stages (Rutab and Tamar). When the fruits are at their early development stage (green/Habakouk), nearly black-indurated patches are sometimes seen on the fruit because of the wind beating the tender fruits against the hard fronds. Recently planted small offshoots can, however, easily be uprooted by strong winds.
The wind could also have an effect on the pollination efficiency; light winds are beneficial and favor pollination while high speed winds will blow away a great deal of the pollen, especially on palms found at the edges of the plantation.
Relation between quality and age of palm trees:
Palm trees have a long life (between 80 to 100 years) and usually, after 5 years, they start to produce dates. Young palm trees usually produce a higher quality of dates. In fact palm trees between 5 and 20 years old produce the best quality and as the trees get older the quality decrease.
The planting operation is divided into different activities which will be discussed separately.
It is difficult to prescribe definite plant spacing but there are specific factors influencing the spacing such as:
- to allow for sufficient sunlight when palms are tall
- to allow for sufficient working space within the plantation
- to provide sufficient space for root development.
Previously, the general assumption for a commercial date plantation was to use a plant spacing of 10 m × 10 m (100 palms/ha). It has, however, changed over time and a plant spacing of 9 m × 9 m (121 palms/ha) or 10 m × 8 m (125 palms/ha), is used in modern plantations.
The planting density also depends on ecological factors (mainly humidity) and on varieties. In general, commercial plantations use 10 m × 10 m, 9 m × 9 m or 10 m × 8 m, for all varieties. The tendency to plant more closely is found when the prevailing wind is dry and extremely hot and strong. The 10 × 10 is desired in areas where humidity during the date ripening period is high. This wider spacing is to allow sun and wind to counteract the humidity's influence. Wide spacing is also recommended whenever there is considerable danger of rain damage to dates during the ripening season.
Time of planting
The critical factor is to transplant the young tissue culture date palms or offshoots at that time of the year that will ensure a good survival rate and proper establishment before the beginning of a "hard" season.
In most of the date regions in the northern hemisphere, spring and autumn are preferred for the planting out of tissue culture-derived date plants or offshoots. Spring avoids the cold of winter and takes advantage of the warm weather that encourages rapid growth, while autumn gives the young shoot a longer time to establish itself before the heat of summer. Each of the two seasons, however, has its corresponding disadvantage; spring, the early approach of the great heat, and autumn, the early approach of the cold.
In the southern hemisphere the best time of establishment is during autumn (February/March) because of the following reasons:
- Winters are relatively frost free,
- Very high summer temperatures,
- Strong, dry winds during August-January, and
- Sand storms during the summer.
In areas without extreme dry, hot summers and with severe frost during winter it is recommended to plant during August/September or at a time safe from the occurrence of frost.
Planting time and depth
Planting should always be initiated early in the morning to limit stress on the date plantlets and also to allow sufficient time for adaptation (from the plastic bag to the soil). Bags are to be removed with care and the plant, with most of its surrounding substrate, to be planted carefully.
Planting is probably the area where most people make the vital mistake of planting the plant too deep. The planting depth is critical because the "heart" of the plant should never be covered with water. Once the plant is covered with water the growing point rots and the plant dies off. If a date plant is planted too shallow, its roots will desiccate and die.
The golden rule is to ensure that the greater diameter of the bulb of the plant is at the same level as the soil surface after transplanting and to ensure that water does not go over the top of the date plant.
Immediately after transplanting, a basin is prepared around the palm to prevent run-off and to ensure a sufficient supply of water to the plant. When using a micro irrigation system, it is recommended to have a basin of approximately 3 m in diameter and 20 to 30 cm deep. The basin should have a slight downward slope towards the plant to allow the water to reach the root system of the young plant.
The benefits of organic material were highlighted when land preparation, as part of the plantation development, was discussed. The mulching is done by putting a layer of organic material (e.g. wheat straw) around the base of the palm. Mulching of the basin has the following advantages:
- Limits water loss from the soil through evaporation;
- Prevents crust formation;
- Allows better water penetration into the soil:
- Limits weed growth around the plant; and
- Improves the humus content of the soil.
Date Palm Propagation
There are three techniques to propagate date palm: Seed propagation, offshoot propagation, and the recently developed tissue culture techniques.
Seed propagation, also called sexual propagation, although useful for breeding purposes, is not a proper method of date palm vegetative propagation, and should be discouraged. Reasons in favor of discouraging seed propagation, are the following:
* Date palm is a dioecious species and consequently half of the progeny will be males and half will be females, with no certain way to determine at an early stage the sex of the progeny, nor fruit or pollen quality prior to flowering (often only seven years later);
* Female plants originating from seedlings usually produce late maturing fruits of variable and generally inferior quality compared to established clonal palms. In a seedling plantation it is rare that more than 10 percent of the palms produce fruit of satisfactory quality;
* Date palms are heterozygous, and thus there will be much variation within the progeny, and desirable characteristics of the parent palm may be lost. In other words, it is not true to type propagation and no two seedling palms are alike;
* Seedlings differ considerably with regard to production potential, fruit quality and harvesting time, making them very difficult to market as one harvest;
* The above reasons result in waste of time, space and money.
Thus, seed propagation is by far the easiest and quickest method of propagation. However, it is not a true to type propagation technique and no two seedlings will be alike. Because of its diversity, the seed approach could only be useful for breeding purposes. When conditions are known to be unfavorable for date fruit production (case of marginal areas), the planting of date seeds, for future selection on fruit quality, is the most economical way of selecting clones that have some desirable characters such as rain and/or salt tolerance.
Offshoot plants are true to type to the parent palm. The offshoots develop from axillary buds on the trunk of the mother plant and consequently the fruit produced will be of the same quality as the mother palm and ensures uniformity of produce. The offshoot plant will bear fruits 2 - 3 years earlier than seedlings.
Offshoots are mainly produced in a limited number (20 to 30 at most) during the early life of the palm (10 to 15 years from the date of its planting) depending on the variety and on prior fertilization treatment, irrigation and earthing up around the trunks. Although 20 to 30 offshoots are produced by a palm, only three or four offshoots are suitable for planting out in one year and must still go into the nursery for 1 to 2 years before field planting. Zahidi, Berim and Hayani varieties are known to produce large numbers of offshoots, while Mektoum and Barhee varieties produce relatively low numbers of offshoots.
The offshoot selected for removal must be disease and pest free and at least three to five years old with a base diameter between 20 and 35 cm, weighing over 10 kg but not more than 25 kg because of handling difficulties. Signs of mature offshoots are the availability of their own roots, first fructification and the production of a second generation of offshoots.
Small offshoots weighing 5 kg and less, if needed, could also be used, but their survival potential will be much lower than that of larger offshoots. They should initially be looked after, for at least two years, in a nursery, or mist bed in a greenhouse or a shade net structure. Fungi are usually a serious problem in a mist bed, and the offshoots must be treated twice a month with a large spectrum fungicide.
The best time for the removal of offshoots and transplanting into the nursery for rooting (never directly into the field) is after the soil begins to warm up in the late spring and early summer (March/April). February/March and September/October are then the most suitable period for field planting, respectively.
Two types of offshoots occur on a date palm tree: the lower and older ones, and the upper and younger ones. It is believed that low offshoots are more active physiologically than high ones; they probably grow faster (the number of leaves produced increases with age). In fact, the high offshoots have fewer carbohydrates than low offshoots, resulting in low roots production and consequently low survival rate. It is also suspected that high offshoots develop when no fruit is on the palm.
After 3 to 5 years of attachment to the parent palm, depending on the variety, offshoots will form their own roots and start producing a second generation of offshoots. Only at this stage they are ready to be removed.
Care and skill, acquired only by experience, is important in order to cut and remove an offshoot properly from its mother palm. The operation, usually carried out by two skilled laborers, starts by irrigation several days before cutting. Soil is then dug away from the offshoot(s) using a sharp, straight-blade shovel (a ball of earth, 5 to 8 cm thick, must be left attached to the roots of the offshoot, with the connection exposed on each side). Roots should at no time be cut closer than necessary, since most of the cut roots die and new roots just emerging are susceptible to injuries.
A specially designed chisel is recommended to cut offshoots.
Lower leaves must be cut off and the remaining ones tied together in order to facilitate handling. Once the loose fiber and old leaf bases are cut away and the connection between the offshoot and the mother-palm is located, the first cut is made to the side of the base of the offshoot close to the main trunk. The flat side of the chisel is put towards the weak point of the offshoot and the beveled side towards the mother palm. Injury must be avoided at all times, the offshoot's tender heart should never be damaged and the cutting operation must be only from one side to obtain a smooth cut surface.
After completion of the removal of the offshoot, the old leaf stubs and lower leaves are cut off close to the fiber and the basal part left bare of leaves. Ten or twelve leaves around the bud are retained and tied close together 6 to 8 cm above the bud with heavy twine or wire. The terminal parts of these leaves extending beyond the tie (20 cm above the tip - centre of the offshoot) are also cut off. It is advised that the cut surfaces of both the offshoot and the mother palm be covered with a copper sulfate product in order to avoid infection by Diploid and other parasites.
Survival of cut-offshoots depends to a large extent on the variety.
It is advisable that an offshoot never be planted into the field directly after removal from the mother plant. A rooting period of one to two years in a nursery is essential in order to ensure an optimum survival rate and to avoid uneven development of the plantation.
In most soils, the early and rapid growth of the offshoot is better when the holes are prepared one to two months before planting. The size of the hole should be one m³ and the holes should be filled with a mixture of topsoil and 10 to 15 kg of manure of high quality (with very little unmatured matter) and NPK fertilizers. The filled holes should be irrigated several times to promote the decomposition of the manure and also to allow the mixed soil to settle in the hole. Well-rotted manure can be used in holes prepared and irrigated shortly before planting, but extreme care must be taken to put the manure (and fertilizers) deep enough to form a layer of soil of at least 15 to 20 cm thick between the manure and the base of the offshoot.
The leaf base of the offshoot should be clearly above the soil level. It is important to plant the offshoot to the depth of its greatest diameter in order to avoid the rotting of the base (if it is too low) and to prevent the water reaching the loose fiber near the bud which causes its desiccation (if it is too high). The plant water basin, of 1.5 to 1.8 m in diameter and 20 to 30 cm deep, should be prepared around the offshoot.
The soil near the newly planted offshoots should be kept moist at all times by light and frequent irrigation. The irrigation frequency is dependent on the type of soil. Very sandy soils require daily irrigation during the first summer. Heavy soils require irrigation only once a week; while in most soils irrigation is required every second or third day. During the first six weeks (or till the appearance of new growth) the date grower should always inspect his/her planted offshoots to make sure that the surface soil does not dry and shrink away from the offshoot. A mulch of hay or straw around the offshoot will enhance moisture contention, weed control and finally improve humus in the basin. Young offshoots and tissue culture-derived plants should be protected from harsh climatic conditions (sun and wind during the first summer and cold the following winter) and against some animals (rabbits, etc.). The use of shade net/hessian wrapping or a tent of date leaves is recommended. The top is to be left open so that new growth may push through.
To summarize, offshoot propagation is true to type but it is not very practical from a mass propagation point of view, and consequently does not satisfy the large needs of plant material. The following reasons illustrate this handicap:
- Offshoot production is limited to a certain period in the palm's life span (a short vegetative phase of about 10 to 15 years);
- During this short phase, only a limited number of offshoots are produced (20 to 30 offshoots, at most, depending on the variety);
- Some varieties produce more than others (some do not produce offshoots at all);
- A mature specimen with no offshoots will be lost if not propagated through another technique;
- Depending on the care given, a low planting survival rate is frequently obtained when using offshoots;
- The use of offshoots will enhance the spread of date palm diseases and pests;
- Offshoot propagation is difficult, laborious, and therefore expensive.
Tissue culture propagation
The application of tissue culture techniques for date palm, also called in vitro propagation, has many advantages:
- Propagation of healthy selected female cultivars (disease and pest-free), Bayoud resistant cultivars, or males having superior pollen with useful metaxenia characteristics which can easily and rapidly be propagated;
- Large scale multiplication;
- No seasonal effect on plants because they can be multiplied under controlled conditions in the laboratory throughout the year;
- Production of genetically uniform plants;
- Economically reliable when large production is required.
Embryo culture involves excising an embryo-aseptically from the seed and planting it in a sterile nutrient medium.
It is important that immediately after transferring saplings to new location do irrigation and they usually keep wet around new trees in the first months. In the first year proper and regular irrigation is very important but as much as trees become older, they become stronger and they need less water. Once the plantation is established, a frequent irrigation schedule is to be followed to allow sufficient water supply to the young date palm. The irrigation frequent is soil type dependant, but on very sandy soils it requires daily irrigation during the first summer. Heavy soils will require irrigation once a week, while in most soils, irrigation is required every second or third day. During the first six weeks, the date growers should inspect their planted date palms to verify that the surface soil does not dry and shrink away from the plant.
Usually, a Piarom sapling needs around 10 years to become mature enough. Of course, this duration depends on climate and soil of each area. In the north of Haji Abad (Dehestan Village), it usually takes more than 10 years because the weather is cooler. For irrigation in Haji Abad area, they use the water which flows in a big river in that area but it is a seasonal river and just during winter water flows. During summer they use water which was extracted from the ground and they guide this water by some piping systems to trees. They usually do irrigation 3 or 4 times during summer. While most growers in Dehestan area use piping system and drip irrigation, some growers still use traditional systems like flood irrigation.
Any water applied when not necessary, is a waste of a precious commodity. For example: if water is applied too late in the season, then it is useless because the crop is already dead or the production suffered so much that there will be no fruit, even though deficient water is then applied over the growing period. The opposite is also true; if too much water is applied, the plant may also suffer. The crop may die due to water-logging.
Different irrigation techniques
This irrigation method is the oldest method known, and is also the method most widely used in date palm culture. It has, however, advantages as well as disadvantages which are outlined below:
(1) running costs are low
(2) easy to apply
(3) initial costs are low if the area is fairly flat.
(1) difficult to achieve a high efficiency rate
(2) labour intensive
(3) irrigates areas in between where no palms are planted
(4) not well suited for sandy soils.
(1) more efficient use of water
(2) running costs are low
(3) easy to schedule/manage
(4) topography is not a limitation
(5) only the water needed by the palm is applied
(6) not influenced by wind
(7) easy to automate
(8) not labor intensive.
(1) expensive (Installation)
(2) requires very clean water
(3) sometimes difficult to determine if the correct amount of water has been applied by the system, and when it becomes clear that it is too little, it may be too late.
Growers fertilize at the autumn after harvest. They usually use the animal fertilizer which is produced by their animals or buy from local ranchers. They usually prepare around 10 to 15 Kg natural fertilizer for each tree and hold down around roots. For a good harvest, this has to be done each two years. Using of chemical fertilizer is not very common among growers, just in recent years a few of growers who use their lands for growing of other crops like wheat, bean and so on, usually use chemical fertilizers like phosphate and Urea.
Time of application
In an effort to obtain the best results from any fertilizer application, it is important to link the stages of application to critical times over the growing period, i.e. vegetative phase, reproduction phase. The same principle applies to date palm fertilization and therefore the time of application is co-ordinated with certain growth phases during the year.
The date season is divided into two growth phases: vegetative and reproductive. The latter is also divided into two stages namely the flower formation stage (February - April in the northern hemisphere and June - August in the southern hemisphere), and the fruit development stage (July - October in the northern hemisphere and November - February in the southern hemisphere). Scheduling the application of fertilizers according to these phases ensures an increase in the amount of properly developed flowers and a potential increase in yield. The best results will be realized when the fertilizer applications are done as soon as possible after the initiation of the two stages (flower and fruit formation). Therefore, it is recommended that these applications take place during February and July for northern hemisphere, and June and November for southern hemisphere.
The most common technique of pollination is to cut the strands of male flowers from a freshly opened male spathe and place two to three of these strands, lengthwise and in an inverted position, between the strands of the female inflorescence. This should be done after some pollen has been shaken over the female inflorescence.
In order to keep the male strands in place and also to avoid the entanglement of the female cluster's strands during their rapid growth, it is recommended to use a twine (a strip torn from a palm leaflet or a string) to tie the pollinated female cluster 5 to 7 cm from the outer end.
This pollination technique is more economical and allows proper use of the pollen as well as adequate control of the timing of pollination. There are several techniques to apply dry pollen:
(a) Cotton pieces: The most common technique of using dry pollen is to dust it on cotton pieces about the size of a walnut and place one or two pieces between the strands of female inflorescences.
(b) Use of a puffer: A small manual insecticide duster, known as a 'puffer' is also used to apply dry pollen. This technique is used either alone or in addition to the cotton pieces technique
(c) Mechanical pollination: It consists of pollinating freshly opened female spathes from the ground with the use of a special apparatus. Mechanical pollination from ground level for three times and with 1:4 (pollen/filler ratio) recommends to achieve high yielding of most date varieties. It seems that the frequency of mechanical pollination as well as the suitable concentration of pollen/filler ratio are the most important factors in date palm pollination.
Satisfying pollination results are obtained within 2 or 4 days after the female spathe has opened. March and April is the normal pollination period in the Northern Hemisphere; July and August for the Southern Hemisphere. Variety and season could delay or advance the opening of the flowers.
Flowering period of male palm
Flowering periods of male and female palms should be synchronised in order to have enough pollen when the female spathes open. It is preferable if the male spathe opens 2 to 4 days earlier than the female spathe. Male palms should receive the same cultural techniques as the female palms and must preferably be planted in areas that receive more sunlight; (i.e. in the northern hemisphere, their exposure to the south favors, in general, early flowering). Lack of irrigation during fall and winter at was found to be the only reason of delaying the flowering date, and consequently resulting in low fruit set.
Date palm bunch covers offer several advantages and are commonly used in the New World of date culture areas in order to protect fruits from high humidity and rain, from bird attacks and also from damage caused by insects.
Protection from high humidity and rain
In various date growing areas rain could coincide with the ripening season and consequently causes severe loss of fruit. A sturdy light-brown craft-paper is used to cover and provide good protection of the bunch during the ripening season. Protection is applied to the bunches in late kimri stage. Paper covers, wrapped around the bunch and tied to the fruit stalk, could be used in combination with a pesticide programmer because the lower part of the bunch is not covered. Covering bunches too early may lead to the sun burning of the outer young fruits, once the cover is removed.
Immediately before the Khalal stage, minute superficial breaks, or checks in the fruit skin occur. The abundance of these checks and their types (transverse, longitudinal or irregular) vary in different varieties. When the checking is severe it is usually followed by a darkening and shriveling of the tip (black nose).
At the Khalal color (yellow to red), checking no longer occurs and water will produce deeper and longer breaks or cracks (splitting phenomenon) in the skin and flesh beneath. Furthermore, humid weather during the Khalal stage also favors the attack by various fungi causing serious spoilage from rot. At the Rutab stage, moisture no longer causes skin breakage, but the fruit absorbs moisture and becomes sticky, less attractive and more difficult to handle. High moisture content of the fruit will result in fermentation and souring that often results in heavy losses. At the Tamar stage, high humidity and rain cause little damage to the fruit except when it is neglected. The timing of bunch protection from rain is usually when the fruit starts to acquire its Khalal color. An early covering will increase checking and blacknose because it reduces ventilation within the bunch. Although, the fruits escape damage by actual wetting, damage by excessive humidity increases.
Protection from birds
Birds of various species cause severe damage by eating on the fruit during the Rutab and Tamar stage. Birds, besides eating the fruits while on the bunches (mostly at the Khalal stage), kick the fruit off the bunches, resulting in the loss of date fruits that fall to the ground. When there is danger of severe bird, it is advised to initiate a bird control system. With the paper bags, the bunch should also be protected beneath with a good grade of porous cloth or netting that will exclude birds and insects, but at the same time not interfere seriously with ventilation of the fruit. The importance of ventilation increases during the later stages of fruit growth and ripening as well as with the frequency of showers and periods of high humidity. If such conditions occur, it is advised to use a cover flared out and not extending down around the sides of the bunch. The thinning of central-strands of a bunch will promote better aeration of fruits. Rings or spreaders 15 to 30 cm in diameter, made usually of heavy wire, could be inserted in the centers to keep the bunches open as the fruit becomes full sized. Such accessory is mainly recommended with short-strands varieties, bearing fairly soft fruits. Those of a many-pointed star shape (or corrugated wire) remain in place better than circular ones and they must be inserted before the fruit reaches the Khalal stage.
Protection from insects
The bags retain the fruit and provide some protection from birds, but they do not hinder fruit-infesting insects. Unless only Khalal fruit is harvested, insects may damage more than 50 % of the Rutab fruit. Stored dates from such palms will show large infestation by living and dead insects.
Physical exclusion of most insects by use of screen bags is a practical measure used in various localities in the Middle East. Moths and other insects larger than fruit beetles (Nitidulidae) are excluded. The bags are of flexible 18 × 20 mesh wire or shade net (80 %) and are 1.0 to 1.5 m2, depending on the bunch size to be covered. It is closely tied to the fruit stalk to ensure that rain water will not enter and also to prevent it from being blown away by wind. The best timing of its placement is mid-to-late chimri stage.
To avoid confusion, one should differentiate between pruning in general terms and pruning in date palm. Pruning in fruit trees and bushes of temperate fruit consists of the removal of living wood, while pruning in date palm is in general the removal of only dead or nearly dead fronds and their bases. Depending on variety and cultural conditions, date palm leaves can remain alive for at least seven years with a maximum activity during the first year and an ultimate decrease in their photosynthetic capacity. As the leaves do not drop of their own accord, they must then be cut off.
Pruning is desirable in order to improve date fruit quality and also enhance the bearing capacity. In fact, when too many leaves (as many as 180 leaves/palm unpruned for 5 to 6 years) are retained and reaching below level of the fruit bunches, a high percentage of fruit affected with checking and black nose and of fruit in the dry grades is obtained. Checking, occurring during mid-summer is increased by high relative humidity caused by lower leaves. Furthermore, such lower leaves probably compete with the fruit, and create favorable sites for diseases and pests. Removing the leaves up to about the point where the lower ends of most fruit bunches are exposed is highly recommended for adult full bearing palms. Pruning is mainly practised after fruit harvest; Pruning could also be realized at any convenient time between the harvesting and the flowering season (thinning period is recommended) and because of the greater ease in cutting, it is desirable to remove them before the bases became hard and dry. The dry, old hanging and withering or diseased leaves are cut along with superfluous offshoots. Leaf pruning could also be synchronised with tying down of bunches or with bagging. It is recommended that leaves which are still green are not pruned so as to take full advantage of photosynthesis. Considerable evidence shows that, other conditions being equal, the fruit bearing capacity of a date palm is in proportion to the number of green leaves it carries.
During the pruning operation, unwanted offshoots should also be removed to foster growth of those that are retained on the palm for propagation, to make access to the palm easier and to promote growth and bearing of the parent palm. In very dense offshoots growth, some of the small plants may be seedlings rather than true offshoots, and must be discarded.
However, where there is any fear of frost in the coming winter, no pruning is recommended and the leaves are left for the protection from the cold of the young tender leaves.
Another important pruning process is the removal of spines, also called thorns. It is advantageous to annually remove spines from the base of new leaves in order to facilitate pollination and handling of fruit bunches. Cut thorns they are a source of some danger, because they lodge in leaf bases on the soil where they persist as a hazard. Date spines are usually removed from the new growth of fronds in the crown of the palm just before the pollination season to allow easy access to the date spathes as they emerge. If the palms have been dethorned the previous year, the new growth will be 2 or 3 rounds of fronds, each round developing 13 new leaves, a total of about 26 to 36 fronds to be dethorned. Such an operation will ensure a safe approach to the spathes for their pollination and also avoid any risk of injury to laborers during other technical practices (tying down, protection of bunches, harvesting, etc.). It is common to use dethorning knives of various designs to remove these spines: a long sharp curved blade or pruning knife mounted on a wooden handle 30 to 45 cm long, or a sickle type blade with a sharp cutting edge.
Harvest season is the most important and exciting season for farmers. all the Date varieties are harvested when all the dates in the bunch or even on the whole palm have less than 20 % water content (of the weight of the fruit). Dates containing more water must be dried (artificially or by the sun) to a level of 16 % to 19 %, to make it possible to preserve them without refrigeration. In this state the fruit has its customary appearance (according to each specific variety), with its characteristic wrinkles and color, ranging from dark brown to light yellow. farmers have to climb the palm trees and cut the branches of dates and by rope send them down. Then make separate dates fruits from branches.
In fact, this is the first step in sorting. In the next step, growers separate defective fruits from good ones. In this step, all dates which were damaged by animals like birds or insects will be separated and then the rest of product will be packed. Usually all these processes are done by growers in near of their gardens. After first sorting and packing by growers, we transfer product to Pariz Nuts factory where we start double sorting. In this stage, we use a machine for washing and polishing dates. By doing this, all external contamination will be removed. After polishing, dates will be transferred to a belt conveyor where again we do sorting and inspection manually. In this stage, dates will be sorted based on size and if there are still bad shaped or defective ones, they will be removed. We can claim our dates are inspected one by one, and this guarantees the quality of our products.