eBusiness Weekly
Special Correspondent
General
Cucumber (cucumis sativus) is a member of the Cucurbitaceal family native to Africa. Cucumber is an annual deep rooted crop with plenty of tendrils and has hairy leaves. Optimum growing temperatures are between 20° C to 25° C. At temperatures below 16°C growth slows down and cucumbers are frost sensitive. Most cultivars are Monaecious, they have separate male and female flowers on the same plant. They are not Parthenocarpic like greenhouse cucumbers which do not require pollination of flowers for fruit production. As Monaecious cucumbers are dependent on bees for pollination it is recommended that two to three hives per hectare are placed near the field. Up to eight bee visits per flower is required to ensure pollination for fruit formation.
Spacing
Spacing rows can be 1,2m-1,8m apart and 50cm-1m apart in row spacing, depending on what plant population is needed and varieties selected.
Plastic mulch can be applied where drip irrigation is used. Plastic mulch helps control weeds, improves the use of water and fertiliser. It also reduces incidents of fruit rot where the fruits are not in contact with the soil.
If cucumbers are to be grown on beds spacing of 1,2m- 1,8m bed centre to bed centre then two rows can be put on the top of the beds.
The rows can be 40cm apart, and in row of 50cm- 80cm apart. Cucumbers can be direct seeded in the ground or seedlings grown in a nursery. If direct seeding is used, then the soil temperature must not be below 13°C or poor uneven germination will take place. With direct seeding the depth of the seed should be 20 mm – 28mm deep. Speedlings need to be covered when transplanted up to the top of the plug. Plant populations can vary from 14 000 per hectare up to 40 000 per hectare.
Trellising
Cucumbers can be trellised in order to achieve better yields with better quality of the fruits. If trellising is used it should be 1,6m up to 1,8m in height. Strong poles are spaced every 4m apart.
A twelve gauge wire is placed about 12cm off the soil level and a 8 gauge wire is pulled on the top. Twine or netting can be strung between the wires so plants can be trained up.
Planning ahead for rotation purposes, if the trellising is used say for a tomato crop then the cucumber crop can follow the tomato crop using the same trellis system saving on double work.
Training needs to be done on a weekly basis to ensure all the vines are tied onto the netting or twine. Pinch out the side shoots from the bottom up to around 50cm, after this leave them to grow out.
Advantages of trellised
cucumbers are:
1)Increased picking efficiency.
2) Better yields.
3) Straight fruits
4) Uniform colour, not like fruits grown on the soil which have a white/yellow area where it has been lying on the soil surface.
5) Reduces fruit loss to soil diseases.
6) Better pest management.
Disadvantages:
1) Extra cost of trellising materials.
2) Extra labour costs to erect, dismantle and training of the vines.
3) Plants are prone to wind damage therefore wind breaks need to be put in wind prone areas by putting up 50 percent shade cloth of 2m height up wind of the crop.
Field preparation
Ploughing or sub soiling needs to be done to a depth to break up a hard pan if present in the soil. The PH should be between 5,5 – 6. Cucumbers are adapted to a wide variety of soil types that have good drainage and adequate water holding capacity. Soil should be harrowed to a reasonable tilth after ploughing or sub soiling so direct seeding can have good soil to seed contact.
Fertilisation
Rates can be based on soil sample analysis results.
Basal: Compound “D” at 600kg – 750kg per hectare can be used.
Top dressing: Apply first application two weeks after germination or transplanting of 50kg per hectare AN. Then every two weeks until first fruit set, then add 35kgs per hectare Muriate of Potash and every two weeks from then on both the AN and Muriate of Potash.
Potassium helps to produce a deep green colour to the fruit as well as firm flesh and helps to produce good yields. Manure or Compost applications improve quality and yields. Up to 20 tonnes per hectare is recommended, as this helps to improve soil texture and improves root growth.
Irrigation
Cucumbers need a constant water supply to enable a good yield of quality fruits.
Generally, soils must not dry out at planting or transplanting. Soil types will depend on the frequency and amount. From flowering to fruit development depending on the weather, amounts should be supplied by checking on evaporation pan figures. Roughly 50mm irrigation is required per week. Normally, drip irrigation is recommended for cucumbers.
Maturity
Generally first harvest from planting takes 45 – 55 days. Depending on disease and pest control cucumbers can normally carry on producing for 14 weeks. At harvest the fruit must have reached full diameter and while the seeds inside are still soft and small. Normally, the average length is between 15cm – 20cm and a diameter 4cm – 7cm. From pollination to harvest is normally 15 – 18 days. Cucumber plants set fruits and develop over a long period of time, therefore marketable fruits extend over a period of time.
Harvesting
Cucumbers are hand-picked. When picking, the fruits should be clipped or snapped near the stem and not pulled off or damage to the vine will occur. Once picked place gently in the picking crate and keep cool and covered with a damp cloth. Once transported to the pack shed keep the fruits cooled down to 10°C for best shelf life. Remove any oversize fruits left on the vine by mistake from the previous harvest as they will drain the plant of all nutrients and can cause yield loss.
Damaged or decaying fruit should also be removed. If cucumbers have to be stored the average shelf life is about 10 – 14 days at a temperature of between 10° C – 13° C, and 90 percent to 95 percent RH.
