TEORIA DE LA REINVENCION DE LOS DERECHOS HUMANOS

By Wolfgang Palme

Botanical name: Cucumis sativus

General crop requirements

Cucumbers need warm, light, free-draining soils that are rich in nutrients and humus. They should be grown with rotation breaks of 4 years. If a closer crop rotation is chosen then it is preferable to use grafted plants.

Figure 4.10 Cucumber trials; on the right showing commercial scale production.

Experimental design

Recommended replicates: at least three.

Cucumber plants can take up a lot of room (depending on variety and fruit length). It is therefore often best to use a ‘double row’ system (staggering the plants) as a way of saving space – as illustrated in Figure 4.2. See also recommendations made by CPVO for cultivation according to variety.

Table 4.19

Typical cucumber plant spacing and numbers of plants required for trials.

North & Central Unheated

North & Central Heated

Mediterranean Unheated (frost-free)

Minimum number of plants / core plot 12 12 12

Minimum size core plot (m²) 10 10 10

Plant density / m² 1.2 - 1.8 1.2 - 1.8 2 - 3.3

Steams density /m² 1.2 - 1.8 1.2 - 1.8 1

Row distance (cm) 1 row: 120 - 150 Double rows: 60/120 – 100/200 1 row: 120 - 150 Double rows: 60/120 – 100/200 1 row: 100 Double rows: 50/100

Sowing and planting

Production season and the length of crop cycle depend on local climatic conditions (e.g. temperature, light etc.) and availability of climate control (e.g. heating) in the greenhouse. If the soil temperature drops below 14-16°C for a prolonged period of time the plants will wilt and die. If the temperature rises too high and there is not enough humidity the main shoots can show leaf burn. High temperatures with high humidity are not conducive to development either – if this happens the crops should be shaded.

Table 4.20

Typical cucumber sowing and harvesting dates.

Region

- Production type

Sowing at Planting at Start of harvest End of harvest Remarks

North & Central

- Unheated April May June September

- Seasonal Heated February March May September

- Long cycle Heated December

June February July March July July October 2 Sets, grafted plants Mediterranean

- Long cycle October November December July

- Short cycle Spring January February March July - Short cycle Autumn August September October February Table 4.21. Temperatures required for the production of cucumber seedlings and plants.

Germination temperature °C Day/ Night

Days until germination

Temperature for seedlings in °C (Day/ Night)

Pot size Weeks until planting

25/ 20

Ventilation from 26 8 - 14 20 - 25 / 18 - 20Ventilation from 26 8 – 13 cm 4 - 6

Table 4.22

Optimal temperatures for cucumber growth and fruit production.

Day Night Ventilation from

Immediately after planting 22 - 24°C 16 - 18°C 25°C

Later in the growing season 20°C 15°C 22°C

Plant nutrition and irrigation

Table.4.23

Cucumber plant nutrient requirements.

Yield expectation (kg/m2₎ N (g/m²) P(g/m²) K(g/m²) Mg (g/m²) 15 25 6 44 7 25 38 10 65 13 40 56 16 88 20

Source: adapted from various sources, see Appendix B. Leaf nutrient contents are given in Appendix C. The crops need 5 - 6.5 l/m² of water each day from May onwards.

Training and pruning

Cucumbers can be grown via two methods using cords (vertical strings tied to a horizontal top wire). Side shoots, tendrils and fruits are removed up to a height of 0.75 m.

For the first method (see Figure 4.11), only tendrils and side shoots are removed from a height of 0.30m - 0.75m. One fruit per axil should be left. The main shoot has to be cut when it reaches the top wire. The last 2-3 side shoots are allowed to hang down from the top wire. This way of pruning the cucumber crop is called “Kring- method”.

For the second method (termed ‘high cord culture’), all the side shoots have to be removed. One fruit in every two is also removed. In this case one axil will be empty, another will have just one fruit. The main shoot does not have to be cut, but grows along the cords. When it reaches the top wire, its cord has to be let down to allow the base of the stem to lie along the ground.

Figure 4.11 Training and pruning of cucumbers according to the Kring method.

Disease and pest infestation, physiological disorders and other abiotic damage • Downy mildew - also affecting lettuce and other vegetables (Pseudoperonospora cubensis).

• Powdery mildew of cucurbits and other vegetables (Sphaerotheca fuliginea and Erysiphe cichoracearum). • Leafspots of vegetables (Didymella bryoniae).

• Sclerontinia sclerotiorum.

• Thrips on greenhouse crops. • Spider mites (Tetranychus urticae). • Aphids, white flies, leaf miners etc. Assessments made during growth

Many parameters can be assessed using a 1 to 9 scale (1 = very low, 3 = low, 5 = medium, 7 = high, 9 = very large / high) but quantitative measurements are preferable whenever possible.

• Number of missing plants. • Uniformity of crop.

• Vigour/density of the crop.

• Regeneration capacity after harvesting. • Internode length.

• Leaf size.

• Colour of the leaves.

• Total length of the plant (at the end of cultivation). Assessments made at harvest

Harvesting should usually begin when fruits have an average weight of more than 400g (later in the year they should reach more than 500g). However, in Northern and Central Europe early fruits of more than 300g are permitted. Harvesting should be done regularly (three times a week). The crop should be sorted according to EU quality standards. Crops are divided into marketable and non-marketable (undersized, rotten, odd-shaped or yellow). Fruits are counted and weighed.

Length and diameter of the fruit should be recorded. At least three times per year ten marketable fruits from the main stem and ten from the side shoots are measured. Diameter is determined at the thickest point.

Evaluation of the following quality parameters are assessed for ten fruits, three times a year: • Ridged fruits.

• Colour of the fruits.

• Relationship between flesh and seed construction. • Shelf-life in days.

Overall value score

This is particularly appropriate for variety trials. It takes into account all the criteria for the cultivation and marketing of the variety based on expert opinion as evaluated by researchers using information from farmers, wholesalers and consumers (1 = very low, 3 = low, 5 = medium, 7 = high, 9 = very high).

References and further information

UPOV Guidelines for the conduct of tests for distinctness, uniformity and stability. Cucumber (TP/61/2). www.upov.int