IN DEMAND: Soil-less gardening uses less water than conventional gardening.

Space-saving soil-less gardening is the next big thing, writes Sacha van Niekerk.

Remember the hanging gardens of Babylon? It turns out mankind has known for a long time that it is possible to grow plants without soil. 

The concept, known as hydroponics, relies on nutrient-rich water and sometimes air - some suggest up to 90 percent less than in traditional gardening methods.

It’s so popular that you can spot amazingly lush hydroponically grown lettuce, chilli, tomato, strawberry and the like on Instagram, and easily buy a hydroponics kit online for your windowsill or office desk. Trends and circumstance have sparked the concept in South Africa, as water storages and escalating food costs have given rise to home gardening.

More and more millennials - and boomers - are into “indoor” plants and they want to eat food knowing where it has come from and how it is grown. The environmentally conscious approach is often referred to as “clean food”.

Which is perhaps why no one is taking offence at the fact that these plants are drawing nutrients from pools of fish - and yes, their manure. Or for that matter, worm castings. (In all fairness, there are various sources of nutrients.)

While it’s tricky to begin with without a kit, hydroponics is said to yield much more all year round and in a smaller space. It’s free of soil pests, and therefore pesticides.

It lends itself well to vertical gardens and there’s no reason why you can’t grown your own groceries in your garage.

It has also, of course, reinvigorated commercial farming.

Keith Tozer and his wife, Fiona, bought a smallholding in Crestholme (between Durban and Pietermaritzburg) in 1983 and wanted to use the property as productively as possible.

“We spent years trying to get the best results we could using normal soil culture, but the soil quality here is not ideal and our supply of water from a borehole is limited, so results were usually average at best. Our interest in hydroponics was sparked earlier when we spent a few years in the Middle East during the 1970s and witnessed the amazing results that were possible in that arid desert region,” Tozer said.

After leaving the corporate environment in 1994, he decided to work full time on the smallholding.

“I researched all hydroponics systems that were developed for commercial growing and decided on the gravel flow technique system because it was the simplest, most robust and versatile system.

“We built our own system in 1995 and it has been in continuous production ever since.” Today, Flow Grow is a commercial grower of a range of vegetables.

“Our produce is sold via third parties to vegetable retailers, hotels, restaurants, schools and hospitals.

"It also costs much less to grow hydroponically than in the soil. This is why hydroponics has become so popular both for commercial and home use,” said Tozer.

A number of different techniques has been developed, using a variety of different mediums.

Common to all systems is the use of a nutrient solution which is water with the nutrients added.

“The techniques differ in the way they anchor the plant and deliver the nutrient solution to the plant’s root system. Some techniques replicate the action of the soil.

"The medium is watered on a cycle, and between watering the medium retains enough of the nutrient solution for the plants to use,” Tozer said.

“This would include all top- or bottom- irrigated systems like drip-irrigated systems, and the flood and drain systems.

"These systems typically use pots, bags or troughs. Mediums like wood shavings, sand, vermiculite, perlite and expanded clay (leca) are used.

“Because the medium absorbs the nutrient solution, it eventually rots and has to be replaced frequently.

"The flow techniques do not replicate the action of soil, but instead deliver the nutrient on a continuous basis.

“This allows for the use of a non-absorbent medium, such as the granite that our systems use.

“Our commercial growing operation has enabled us to evaluate and experiment with many of the hydroponic techniques that have been developed.

“The gravel flow technique proved to be the most practical, robust and efficient system. Everything grows quickly, plants are of a uniform size, and all are of fantastic quality and taste,” said Tozer.

What are the benefits of hydroponics?

Excellent results

The balanced nutrient supply ensures that the plant is being perfectly fed and watered, resulting in rapid, even growth, larger yields and very nutritious and tasty produce. No special gardening skills are needed to use the system.

Cost effective

The system is so efficient that the costs of growing are much lower than growing in soil. A reticulated hydroponics system will use about one tenth of the water and fertiliser required to grow the same plants in soil. The pump’s electricity consumption is negligible.

Efficient use of nutrients

For good growth results, a plant needs a balanced nutrient supply. Soil, supplemented by additional composts and fertilisers, is the nutrient source in normal soil culture. It is not easy to identify exactly what salts and trace elements are in the soil. Often fertilisers are used to try to create the balance. For example, super phosphate to add phosphorous. Very little of the fertiliser added to soil is ever used by the plants. In our system, all of the nutrients are used by the plants - none are wasted and no crop rotation needed.

Efficient use of water

Other than a small loss by evaporation, all water used by this system goes into the plant growth process, either to be stored in the plant or released through transpiration. With soil culture, 90 percent of the water is not used by the plants - it just drains away.

Excellent root aeration

The provision of oxygen to the root system is an essential element of growth. The bubbling of the nutrient solution as it passes through the gravel medium creates excellent aeration.

Rapid growth

The plant root size develops according to the amount of nutrients available. Poor soil will result in a big root system. Good soil will result in a smaller root system. With hydroponics, where the nutrient solution is perfect the root system does not grow large, and the energy goes into the plant body resulting in quicker growth.

Few weeds

Eliminating soil to a large extent eliminates weeds. Wind or mechanically introduced weeds are easily removed. With soil culture there is a lot of fertiliser wastage on weeds.

Labour saving

No soil preparation is required. Weeding is minimal. There is no watering required. Planting and harvesting are quick and simple.

Rewarding

It is great fun and very rewarding to grow your own food. Many of our users also say they find spending time with their system is very therapeutic.

Space efficient

Because the root systems do not grow massive, plants can be planted much closer together than in soil. Enough space has to be allowed for the top structure only and not for the root system. In soil, the root system is usually about twice the diameter of the plant. With hydroponics, it is about half the diameter of the plant.

Versatile

This system can be set up and used anywhere - outdoors in the open, under shade cloth or plastic, on a verandah, patio or sunroof, or indoors under special lighting.

Elevated

The elevated system brings the working height to a standard counter level, completely eliminating bending and crouching working positions.

Being elevated improves air movement around the plants, and reduces disease and pest risks.

Hygiene and cleanliness

The exclusion of all dung and compost from the fertiliser programme eliminates the danger of spreading diseases such as gastro-enteritis. All produce grown in the system remains clean and hygienic from planting to harvest.

Easy to operate and maintain

Provided there is an uninterrupted electrical supply to the system, it only requires topping up with nutrients and water and very little maintenance.