Ground lay gravel flow technique systems for commercial growers
The gravel flow technique has been used commercially in South Africa since the late 1980s. Our own system was built in 1995 and has been in continuous production ever since. The system has been used with great success to grow a range of salad lines like lettuce and celery. Over the years we have grown many different crops and all have grown well. The system is robust and simple to operate and has required only the occasional maintenance and repair. Typically the system is set up in a simple pole and wire shade cloth structure to provide protection from the heat of the summer sun, hail, heavy rain, wind, birds and other animals. The site must be prepared correctly to provide the required gradient for the beds. Beds are usually 30m long and 1m wide. Unlike our tray system these systems use two tanks. The nutrient is gravity fed from an elevated header tank through the beds and returned to a (usually buried) sump tank. It is pumped back to the header tank at intervals. This limits reliance on and consumption of electricity. The gravel beds are constructed directly onto the prepared platform using a steel and wire frame with a flexible plastic sheeting. Each bed can be isolated individually with an inlet valve. Feed and return plumbing is buried to avoid damage and heat build up. A thin layer of gravel is laid in walkways to promote cleanliness and limit weed growth.
For many years we have been assisting growers to set up commercial systems. Over this time we have fine tuned the systems based on our own experiences and now manufacture a number of components which were previously not available off the shelf. These include bed steel requirements, inlet and outlet manifolds and system dosing stations.
We are able to supply all materials for the construction of the shade house and the commercial gravel flow hydroponics systems. While the systems can be configured to any size, we recommend that they are set up in 1000sq m (shade house) units. This optimises the cost per sq m growing space, enables the use of manageable sized tanks and piping, and limits ground preparation work to 40mx40m platforms. Each system provides 720 sq m of gravel beds. Multiple units can be erected to provide the required growing space per site. A viable vegetable production business would require a minimum of two units. We do not usually supply the stone medium or the structure poles as much of the cost is in transport, and they can usually both be purchased closer to site. We do supply the following.
Shade cloth - pre-stitched panels
Wire and wire strainers, bolts and nuts
Steel, wire, plastic liners, staples
Flowgrow bed feed and return manifolds
Feed and return valves, pipes and fittings
2 x tanks, 220v submersible pump, pipes and fittings
Float switch and 220v dol starter
Water mains feed - inline stopcock and ball float valve
Flowgrow dosing station
Wire strainer Heavy duty stapler
Structure erection guide
System construction guide
System operation guide
Hanna pH meter
Hanna EC meter
Stihl mist blower - optional
Our construction manuals and plans for the structure and the hydroponics systems are comprehensive enough to allow for the work to be done by a competent artisan or DIY enthusiast with a small team of labourers. Such a team well managed and using the correct tools can construct a single system in approximately six weeks. (Including the shade house structure). We do not undertake construction or installation work. The manuals are specific to the materials and assemblies supplied and are not sold separately. Our manuals cover the following topics and include detailed plans and diagrams.
Digging holes and planting poles
Bolting cross members
Structure wire installation
Installing shade cloth
Bed steel installation
Bed plastic liner installation
Tanks, valves and piping installation
Stone medium installation and washing Commissioning the system
Daily routine / general
Managing power failures
A selection of pictures showing a number of different systems and crops
The structure is a simple pole and wire constuction with the top pitched to ensure that any occurance of hail does not collapse it. The shade cloth gives protection against hail, heavy rain, wind, large insects, birds and animals, and takes the heat out of summer sunshine while allowing in maximum light.
The gravel beds are constructed directly onto the compacted earth of the platform. The flexible plastic sheeting is folded and stapled over a peg and wire frame. Our own plastic has lasted 20 years without requiring replacement. A thin layer of gravel is placed in the pathways to reduce weeds and keep the work areas free of mud and dirt.