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Information sheets   |   Elsenburg infopaks   |   Crops, vegetables: 11

Vegetables under protection (tunnel farming) Afrikaans | Xhosa

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The cultivation of vegetables within the protection of plastic tunnels was first practised in the Republic of South Africa during the early seventies and spread to the north where the largest areas planted with vegetables and flowers occur today.

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The advantages of using a water culture (hydroponic method) of cultivating vegetables under protection are that the vegetables are very nutritious and that large yields of a high quality can be obtained.

In order to practise this method, the following are necessary:

  • A wind-free area. If this is not possible, windbreaks must be erected or planted.
  • Water must not be very saline. Remember: the water is further enriched by the addition of fertiliser for the plants in the tunnel.
  • The tunnel must preferably be situated close to a market, because the harvest must reach the market place as soon as possible.

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To avoid attacks by soil-borne diseases, the plants are planted in black plastic bags that have a capacity of 15 to 20 l and draining holes 2,5 cm above the base of the bag. The bag is filled with vermiculite, pearlite or rotted pine bark.

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This is very expensive, however, therefore pine sawdust mixed with shavings, can be used as a growth medium. The sawdust/shavings mixture must be obtained from untreated pinewood.

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The seeds are planted in plant blocks/seed-trays filled with a seedling growth medium. The seeds are sown one seed to each compartment of the seed tray, lightly covered with the growth medium and kept wet. The seedlings remain in the seed tray until they have grown to about 10 cm.

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They are then planted in the planting bags and kept wet. Climbers are trained up to overhead wires by pieces of string. The bottom part of the string is placed in the planting hole. The plant is placed on top of the string and firmed down into the growth medium to remove air from the roots. Then the other end of the string is fastened to the overhead wire.

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Tomatoes, cucumbers, green peppers, beans and sweet melons can all be trained up in this way to the wires that are strung above the rows and are fastened to the roof of the tunnel. The string is constantly wound around the main stem of the plant. This applies to all the plants except green peppers, in which case three or four stems can be used.

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All fertiliser must be added to the water with which the plants are watered three to five times a day. The water with the fertiliser must be applied until it runs out of the drainage holes at the bottom of the bag.

The fertiliser to be used is SOL-U-FERT plus Microfeed plus calcium nitrate. The mixture must have a pH of 6,5 and a conduction of 2,0 milli-Siemens per cm for cucumbers and 2,5 milli-Siemens per cm for tomatoes.

Insects often attack plants in plastic tunnels; therefore a spraying programme is essential.


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Tomatoes, English cucumbers and green peppers are at present being cultivated in tunnels. Green peppers and tomatoes can also be cultivated under shade netting. Lettuce, spinach and celery are cultivated mainly under shade netting. In this case, the crops are cultivated in gravel beds and not in tunnels and planting bags.

PC Maree
ELSENBURG / University of STELLENBOSCH