1. Taxonomy and Origin
2. Economic importance and Geographical distribution
3. Morphology
4. Edaphoclimatic requirements
5. Vegetal material
6. Growing techniques
6.1. Soil Preparation
6.2. Settings for planting
6.3. Direct sowing
6.4. Trellising
6.5. Shoot thinning
6.6. Leaf thinning
6.7. Watering
6.8. Fertilization
6.9. Fruit thinning
7. Pests and Illnesses
8. Physiopathology
9. Harvest
10. Nutritional Values

1. TAXONOMY AND ORIGIN

The cucumber belongs to the Cucurbitaceae family, whose botanical name is Cucumis sativus.

Family	Cucurbitaceae
Genus	Cucumis
Species	C. sativus
Scientific name	Cucumis sativus
Common name	Cucumber

Cucumber is native to tropical regions of southern Asia, having been cultivated in India for over 3,000 years.

From India it extended to Greece and then to Rome and subsequently was introduced into China. The cucumber crop was introduced by the Romans in other parts of Europe; records of this crop appeared in France in the ninth century, in England in the fourteenth century and in North America in the mid-sixteenth century as Columbus took cucumber seeds to America.

The first hybrid appeared in 1872.

2. ECONOMIC IMPORTANCE AND GEOGRAPHICAL DISTRIBUTION

Cucumber growing is very important because it has a high rate of consumption; it can be served as fresh or industrialized product. The cultivation of this vegetable is stable in terms of cultivated area (between 7000-8000 ha), but production and exports are increasing.

	Production in 2011 (t)	World Production (%)
1. China	47310000	73,16
2. Iran	1819000	2,81
3. Turkey	1749174	2,70
4. Russian Federation	1202360	1,86
5. Ukraine	966000	1,49
6. United States of America	772720	1,19
7. Spain	720198	1,11
8. Egypt	665070	1,03
9. Japan	584600	0,90
10. Indonesia	521535	0,81
11. Poland	510892	0,79
12. Iraq	495616	0,77
13. Netherlands	430000	0,66
14. Uzbekistan	430000	0,66
15. Mexico	425433	0,66
16. Saudi Arabia	400073	0,62
17. Kazakhstan	334000	0,52
18. Republic of Korea	303805	0,47
19. Thailand	261400	0,40

Cucumber crops are important in several Spanish regions, being species whose agronomic value lies in its seasonal production, which needs to be developed in a protected cultivation (the province of Almería covers about 55% of the total cultivated area).

Spain is the third largest producer in the European Union, with a volume of approximately 720,000 tons. The first place is the Russian Federation with approximately 1,200,000 tons and the second place is Ukraine with 960,000 tons. All data refer to the year 2011.

3. MORPHOLOGY

- Plant: herbaceous annual climber.

- Roots: Very strong root system. It consists of main root, which branches out rapidly into very fine and elongated superficial secondary roots which are white in colours. Cucumber has the capacity to create adventitious roots above the base of the stem.

- Stem: The stems are angular and thorny, creeping and climbing, reaching up to 3,5 meters long, with nodes at the point where a leaf and a tendril sprout. In the leaf axils, lateral buds and one or more flowers are developed.

- Leaf: Simple long petiole and large heart-shape leaf lamina, with three lobes which are more or less pronounced (the centre is more pronounced and generally has pointed end), dark green in colour and covered with a very fine down. The leaves are alternately and oppositely positioned to the tendrils.

- Flower: Flowers have short stalk and yellow petals. They sprout in each leaf axil and can be hermaphrodite or unisexual.

The first known crops were monoecious and had male and female flowers. At the beginning of flowering, there are only male flowers. Afterwards, there will be an equal proportion of male and female flowers in the middle part of the plant and finally at the top part, the female flowers will predominate. The percentage of male and female flowers varies depending on weather conditions.

. Induction of female flowers: short days, low temperatures and enough water.
. Induction of male flowers: long days, high temperature and insufficient water.

Currently, all commercial varieties grown are gynoecious plants, ie, have only female flowers that are clearly distinguishable from the male because they are carriers of an inferior ovary.

- Fruit: The fruit is a fleshy, smooth or rough berry, depending upon the variety. The epicarp changes from green colour, in its immature state, to yellowish orange once the fruit is ripe.

The pulp is watery and whitish in colour, with seeds on the inside situated throughout the length of the fruit. The number of seeds varies and they are oval and slightly flat in shape and tend to be whitish yellow in colour.

4. EDAPHOCLIMATIC REQUIREMENTS

The proper management of climatic factors together is essential for the proper functioning of the crop, since all are closely interrelated and the action of one affects the other.

- Temperature: it is less demanding in hot condition than melons, but more demanding than courgettes.

Temperatures during the day, ranging between 20°C and 30°C, have scarcely effect on the production, although at higher temperatures up to 25°C, early production can be higher. Above 30°C, imbalances in plants are observed which directly affect the processes of photosynthesis and respiration. Nighttimes temperatures at or below 17°C can cause malformations in leaves and in fruits. The critical temperature which ranges from 12°C to 1°C causes frost damage (general plant wilting is difficult to recover).The use of a double-covered vine type greenhouse is useful for increasing the temperature and enhancing the cucumber production system. Temperatures above 40°C cause the cessation of growth.

- Humidity: The cucumber is a plant that requires high levels of humidity due to the large surface area of its leaves. The optimum relative humidity during the day is 60-70% and at night between 70-90%. However, excess moisture during the day can reduce the production by reducing the results of transpiration and photosynthesis, although this situation is not frequent.

In places where humidity level is above 90% and with a saturated steam atmosphere, the condensation on the crop or the dripping from the roof may cause fungal diseases. In addition, a wet plant in the morning will start working later because the first energy available will be used by the leaves to evaporate water from its surface.

Low relative humidity causes fruit burns, rapid development of red spider and even thrips.

- Light: The cucumber plant will grow, flower and produce fruit in a normal way even when daylight hours become shorter (less than 12 hours of light). However, it will also tolerate a high intensity of light. The greater the amount of sunlight, the more abundance of crop yield will result.

- Wind: The presence of wind accelerates water loss and decreases the relative humidity which increases water requirements. Consequently, it decreases fertilization due to inadequate moisture floral styles; it stops the growth of the plant, reduces the production and accelerates plant senescence.

- Soil: The cucumber can be grown in any types of loose soil as long as it is well drained and with sufficient organic matters. It is a moderately salt-tolerant plant (somewhat less than the melon plant). If the concentration of salts in the soil is too high, plants absorb with difficulty the irrigation water, the growth is slower, the stem is weaker, the leaves are smaller and darker in colour and the fruits are twisted. If the salt concentration is too low, the result will be reversed, giving more leafy plants, which are more sensitive to various diseases. The optimum pH is between 5,5 and 7.

For optimum crop growth, soil temperature should be between 18-20°C and the minimum should be between 12-14°C.

5. VEGETAL MATERIAL

The main criteria for the selection of vegetal material are the following:

- Characteristics of the commercial variety: plant vigour, fruit characteristics, disease resistance, etc.
- Target market.
- Greenhouse structure.
- Soil.
- Climate.
- Quality of irrigation water.

Key aspects to consider in choosing the crop variety that suits the growing conditions and consumer preferences are:

- Commercial production which must be as high as possible.
- Plant vigour that allows long cycle and good tolerance to low temperatures and shortening days.
- Strong resistance to diseases (mildew, powdery mildew, etc.).
- Length of fruit, which should be standard (minimum of 30cm and a maximum of 38cm) and stable to different growing conditions.
- Firmness and fruit conservation, which must be adequate to withstand transport and can stay long enough in the market in good condition.
- Other aspects to be considered are earliness of production and fruit characteristics (length, color, stripes, etc.).

Most cultivated varieties of cucumber are hybrids, having demonstrated a higher productivity compared to non-hybrid. They are characterized by:

- Best quality (higher weight, good and uniform color, greater mechanical resistance ...)
- Higher productions
- Increased tolerance to pests and diseases

They can be grouped into the following types:
- Short and cucumber pickle ("Spanish type"). They are small-fruited varieties (maximum length of 15cm), green epicarp with yellow or white stripes. They are used for fresh consumption or for pickling (in this case they are collected smaller). Varieties can be monoecious, gynoecious with pollinator and parthenocarpic gynoecious.

- Medium length cucumber ("French type"). Varieties of medium length (20-25 cm) are either monoecious or gynoecious. Within this type, it is differentiated the variety whose fruit has thorns from the one which has a smooth epicarp or minicucumber (similar to "Almería type", but shorter). It is fully parthenocarpic bloom.

- Long cucumber ("Dutch type"). Variety whose fruits exceed 25cm in length, gynoecious, completely parthenocarpic fruits and smooth epicarp, more or less furrowed. The leaf size is much larger.

6. GROWING TECHNIQUES

6.1. Soil preparation

The ground is prepared by passing the plow and the harrow to leave it with a fine texture that favours the development of crop roots.

6.2. Settings for planting

For early crops with the intention to subsequently remove them early to make a spring crop, the distances are shorter (1,5m x 0,4m x 0,5m or 1,2m). The planting density conditions in southeast Spain can range between 11,000 and 13,000 plants/ha. If the crop being sown is a later crop or the idea is to extend production on into the colder months, then the settings for planting will be increased in order to reduce planting density with the aim of avoiding competition for light and providing proper ventilation.

6.3. Direct sowing

The cucumber is planted in pads or seedbeds or directly on the ground.

Planting is done in pits of 2-3 cm depth in which are placed 3-4 seeds. It is thinned after leaving 1-2 plants only.

6.4. Trellising

Trellising and tying the plants is a must in order to maintain them in an upright position; it will also improve general air circulation and will make it easier to take advantage of the sunlight and to undertake all of the care necessary with relation to crop production (pruning, harvesting, etc.). This will benefit the final production, fruit quality and disease control.

The tying is usually done with polypropylene thread which is tied to the basal end of the ground area (bundled, knotted or attached by loops) and to another wire located at a certain height above the ground. As the plant grows, it will be fastened or tied up to the stake until the plant reaches the wire. Once the plant reaches the wire, it will then move towards the next wire situated at a distance of 0,5m away, while at the same time leaving a trailing shoot over the wire.

Several types of espalier trellising:
- Trellis on inclined plane:
Distance between stake: 4m
Row spacing: 0,40m

- Trellis Type A (planting on both sides of the trellis):
Stakes joined at one end
Distance between stakes: 1-1,30m

- Vertical trellis/espalier

6.5. Shoot thinning

With regard to cucumbers of the "Dutch type", the side shoots are removed in order to leave the plant with a single main stem. The thinning method is similar to other types of cucumber, although the side shoots are not eliminated but blunted from the second leaf upwards.

6.6. Leaf thinning

The old, yellow or diseased leaves should be removed. When humidity is too high, it will be necessary to treat the cuts with paste fungicide thinning.

6.7. Watering

Initially, we must conduct a thorough pre-sowing irrigation to achieve adequate moisture at the time of planting.

Subsequently, in order to force a good rooting, water stress can be provoked. In this way, the root system is able to become more widespread and explore more floor space.

6.8. Fertilization

In protected cucumber crop in southeast Spain, water intake and much of the nutrients are widely applied by drip irrigation. Their applications depend on the growth stage of the plant and the environment in which it develops (soil type, climatic conditions, water quality, irrigation, etc.).

In soil and sanded cultivation, setting the timing and amount of irrigation is determined basically by the following parameters:
- Soil moisture tension, which is determined by the proper use of tensiometer.
- Soil type (field capacity, saturation rate).
- Evapotranspiration.
- Efficient Irrigation (flow uniformity of the droppers).
- Quality of irrigation water (the poorer the quality of water, the higher the salinity level is, and the volume of water needed to move the salts is higher).

- Media consumption (l/m²·day) of cucumber "Dutch type" growing in greenhouse.
Source: Agricultural Technical Documents. Experimental Station "Las Palmerillas". Caja Rural of Almería.

MONTHS	AUG		SEPT		OCT		NOV		DEC		JAN		FEB
Fortnights	1ª	2ª	1ª	2ª	1ª	2ª	1ª	2ª	1ª	2ª	1ª	2ª	1ª	2ª
A	1,63	2,95	3,68	3,80	4,21	3,39	2,40	2,04	1,78	1,41	1.19	1,31	1,53	1,69
B		1,48	2,75	3,04	3,51	3,39	2,40	2,04	1,94	1,41	1.19	1,31	1,53	1,69
C			1,38	2,28	2,81	2,83	2,40	2,04	1,94	1,41	1.46	1,31	1,53	1,69
D				1,14	2,11	2,26	2,00	2,04	1,94	1,41	1,46	1,31	1,53	1,69
E					1,05	1,70	1,60	1,70	1,94	1,55	1,46	1,61	1,53	1,69

A: sowing or transplanting 1^st half of August.
B: sowing or transplanting 2^nd half of August.
C: sowing or transplanting 1^st half of September.
D: sowing or transplanting 2^nd half of September.
E: sowing or transplanting 1^st half of October.

There is another less widely used technique which consists of removing the liquid phase of the soil by suction through a porous ceramic and subsequent determination of the electrical conductivity.

In cucumber "Dutch type," it is very important to maintain a constant humidity level and elevated floor for optimal root development and, subsequently, during the time of fruit formation and fattening. On sanded grounds, the roots develop preferably in the organic material layer located between the sand and soil, so a stable humidity in this area should be maintained, which is usually achieved by watering every 2 days.
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When the crop reaches maturity stage, with a height higher than the stake, coinciding with the temperatures in early autumn, the frequency can be minimized, watering every 3 or 4 days with the same volumes. When the water is of poor quality, irrigation should be performed daily to avoid salinity problems, keeping track with a tensiometer 10-15cb, in order to avoid root suffocation.

In hydroponic crops, irrigation is automated and there are different systems to determine crop water needs, the most widespread is the use of demand-irrigation tray. The time and amount of irrigation depend on the physical characteristics of the substrate.

With regard to nutrition, it is important to take into account the ratios of Nitrogen/Potassium throughout the whole crop cycle, which is usually 1/ 0,7 from transplant to the fourth-fifth week, changing to 1/1 until the beginning of fruit fattening and later on to 1/3.

Phosphorus plays an important role in rooting and flowering stages, as it is crucial for the formation of roots and size of the flowers.

Calcium is a very important element in enhancing plant quality and promotes plant resistance to diseases.

The microelements, mainly iron and manganese, will noticeably affect the color of the fruit, the quality and vitality of the plant.

At the time of fertilization, there is a very wide range of fertilizer applications in which no substantial differences are observed in the crop, given the fact that varied and contradictory application methods can be found in the same area with the same soil type and the same variety. However, in order not to make great errors, the total dose of fertilizer should not exceed above 2g/l, being advisable is to provide 1g/l for water conductivity of 1ms/cm approximately.

There are two methods which are basically used today in order to establish the nutritional needs: first, based on the extraction of the crop, on which there are wide and varied bibliographies, and second, based on an "ideal" nutrient solution to which applications will be adjusted after conducting water analysis. The latter method is the one used in hydroponics, and for it to be carried out in ground or sanded crops, it requires the placement of suction probes to determine the composition of the soil solution through macro and micronutrients analyses, CE and pH.

The most widely used are simple fertilizers: in soluble solid form (calcium nitrate, potassium nitrate, ammonium nitrate, monopotassium phosphate, monoammonium phosphate, potassium sulfate and magnesium sulfate) and in liquid (phosphoric acid and nitric acid) due to its low cost and they allow easy adjustment of the nutrient solution. However, complex crystalline solid and liquid fertilizers also exist in the market that can be used alone or in combination with simple fertilizers, to keep the balance required at different stages of crop development.

The contribution of microelements, which had been largely neglected in the past, is vital for proper plant nutrition. There is a wide range in solid, liquid and mineral chelates form in the market, when it is necessary to promote the absorption of nutrients and the stability of the plant.

There are also numerous deficiency correctors both macro and micronutrient which can be applied through foliar or drip irrigation. Examples are aminoacids - for preventive and curative use, which help the plant at critical stages in its development or under unfavorable environmental conditions and other products (humic and fulvic acids, saline correctors, etc.) that improve environmental conditions and facilitate the assimilation of nutrients by the plant.

6.9. Fruit thinning

Fruits should be eliminated from the first 7-8 leaves (60-75cm), so that the plant can develop a strong root system before going into production. These fruits located on the lower part of the plant are often of poor quality for they touch the ground. They also prevent the normal development of the aerial part and consequently limit the production.

The curved, malformed and aborted fruits and must be eliminated as soon as possible, as well as those that appear clustered in the leaf axils of some varieties, leaving only a single fruit per axil. This facilitates the filling of the remaining fruits and also contributes to early fruit maturity.

Author:
Infoagro