greenhouses I shade net I hydroponics I aquaponics
Soilless cultivation of lettuce, tomatoes, peppers and cucumbers has over the past two decades gained popularity in South Africa because of improved yield and quality. The majority of vegetables in South Africa were always grown in open field systems, but undercover farming yields much higher whilst using less water. Hydroponics and even aquaponics (where fish are used to enrich the water under the plants) are being practiced under protection, e.g. shade net houses and greenhouses.
Hydroponics production for the new
entrant to fresh produce farming
T
he ARC-Roodeplaat mainly utilizes two hydroponic systems, i.e. gravel film technique (closed system) and open bag systems for research trials. These two systems are commercially used in South Africa. The Gravel Film Technique (GFT) is the most popular re-circulating hydroponic system in South Africa especially for new entrants to greenhouse production. They produce leafy vegetables in a gravel film system, with a well-balanced nutrient solution that is pumped to the top of hydroponics system lines and flows down a 3% slope by gravity. The nutrient solution is collected in a reservoir at the bottom and is pumped back through the hydrolines (re-circulated). The gravel’s major role is to give support to the plant, cover the root system and prevent the nutrient solution from being exposed to sunlight. Different types of lettuce, celery, leafy herbs (e.g. parsely, basil), spinach and Swiss chard, leeks, spring onion, chives, different types of cabbage and mustards can be produced in this system. In an open bag system, plants are grown in a plastic bag filled with a grow medium (e.g. sawdust, coir or cocopeat) where nutrient solutions are dripped onto the growth medium and there is a drainage allowance of 10-15%. The system is utilized in shade net houses or plastic tunnels with or without temperature control – this can be manually controlled by opening doors or the sides of the greenhouse.
18 Undercover farming I
July/August2020
Tomatoes, sweet The population increased tremendously pruning, and peppers and comparative in South Africa and improvement of cucumbers are the standard of living has resulted in performance the major fresh of vegetables an increased demand for fresh produce such as products grown of high value and quality. in an open bag tomatoes, hydroponics cucumbers, system in a plastic covered tunnel. The lettuce and peppers in different open bag system is well adapted for production systems. The current the production of tomatoes, peppers, research can be summarized as follows: cucumbers, strawberries, and beans. Production systems for tomatoes ARC-Roodeplaats’ research is focused Tomatoes are widely grown in South on fertigation of lettuce and tomatoes, Africa and rank second cultivar evaluation, stem and fruit 19
I Volume 17 No 4
Trelissed plants are producing much more in a greenhouse than on open land and uses less water.
