In an NFT system, plants are supported in slightly sloping channels rather than soil. A shallow flow of nutrient-enriched water moves continuously along the bottom of each channel and across the roots. Plants take up the water and nutrients they require, while the remaining solution continues to the end of the channel.

At the South Australian farm, the solution was collected at the end of each raised bench through larger collection pipes before flowing into a below-ground return system. It then returned to the central nutrient reservoir, where it could be filtered, adjusted for nutrient concentration and pH, and pumped back to the growing channels, creating a continuous recirculating loop.

Small pots help protect young plants during heavy rain

Another feature that caught my attention was the use of small support pots. The pots support young plants during establishment while allowing roots to grow through the bottom and into the nutrient channel. A small amount of growing medium holds the seedling and developing root system together.

The grower explained that these pots are particularly useful during heavy rain. Because nutrient solution is continuously flowing through the channels, the main concern is not waterlogging but heavy rain washing growing media from the planting hole and disturbing newly established roots. The support pot helps hold the media and root ball together until the root system is established, after which it can be removed.

Heavy rainfall can dilute the nutrient solution within a recirculating system, requiring growers to monitor electrical conductivity (EC), pH and reservoir volume and make adjustments as required. This is particularly relevant in WA, where winter rainfall and occasional intense rain events should be considered in system design.

Greater control over water and nutrition

One of the main attractions of NFT is the level of control it can provide over water and nutrition. In conventional field production, irrigation water and fertiliser move through the soil, where availability to the crop is influenced by soil texture, drainage, salinity, pH and other factors. In a hydroponic system, the grower directly manages the nutrient solution supplied to the root zone. EC provides an indication of dissolved nutrient and salt concentration, while pH influences nutrient availability, and commercial systems may automate some of this monitoring and adjustment.

Because water is recirculated, water not immediately taken up by the crop returns to the reservoir rather than being lost below the root zone. This could be particularly attractive in WA, where irrigation efficiency and access to suitable water are increasingly important considerations for growers. The system also reduces some of the variability associated with soil production. Poor or non-wetting soils, differences in soil texture and uneven fertility become less important when plants receive water and nutrients directly through the hydroponic system. However, greater control does not necessarily mean easier production. Hydroponics reduces some field-production variables but requires more precise management of water, nutrition and equipment.

Heat is likely to be one of the major challenges for outdoor NFT production in Western Australia. During summer, exposed growing channels, pipes and tanks can absorb solar radiation, causing the circulating nutrient solution to warm as it moves through the system. Warmer water holds less dissolved oxygen, while high root-zone temperatures can place additional stress on plants and increase the risk of root health problems.

Return water also travelled through below-ground pipes, while pumps, filters and nutrient-management equipment were housed under cover.

For WA conditions, however, an underground reservoir should be viewed as one part of a broader heat-management strategy rather than a complete solution. During prolonged hot weather, nutrient solution can still gain considerable heat in exposed growing channels. Depending on region and season, growers may also need to consider shade structures, larger reservoirs, temperature monitoring and, where justified, additional cooling.

The suitability of outdoor NFT is likely to vary considerably across WA growing regions. Around Perth, Peel and Gingin, the system could suit autumn, winter and spring leafy vegetable production, while summer production would require careful management of heat and hot easterly winds. The South West may provide more favourable summer temperatures, although growers would need to consider cooler winter conditions, frost risk and higher rainfall.

Geraldton and Carnarvon present different conditions. Winter temperatures may provide opportunities for leafy vegetable production, but summer heat, wind and water quality would present significant challenges, making shade, cooling and careful water management increasingly important.

The key point is that a system performing successfully in South Australia cannot simply be copied and expected to perform in the same way in WA. System design needs to reflect the local climate, water source, crop, market and management capacity of the business.

Water quality becomes even more important

Recirculating water can improve water-use efficiency, but it also means growers need to understand their source water.

As plants take up water, salts not absorbed by the crop can remain in solution and gradually accumulate. This is particularly relevant for WA vegetable businesses using bore water, where groundwater quality can vary significantly and contain sodium, chloride, calcium, magnesium, bicarbonate and other dissolved minerals.

These minerals can affect plant growth, nutrient availability and fertiliser formulation, while contributing to deposits in filters, pipes and other components. A comprehensive water analysis should therefore be one of the first steps before designing a commercial hydroponic system. Once operating, regular monitoring of EC, pH, nutrient-solution temperature, dissolved oxygen and reservoir levels remains important.

Although positioning the reservoir underground may provide temperature-management advantages, it must remain accessible for inspection, cleaning and maintenance.

Crop health risks can spread quickly

Growing without soil does not mean growing without disease. Root pathogens can be particularly important in recirculating hydroponic systems because the water connects plants across the production area. If a problem enters the nutrient solution, it may spread to many plants sharing the same reservoir. Good hygiene, regular crop inspection and early detection are therefore critical.

Where practical, production areas could be separated into different hydraulic zones rather than connecting the entire crop to a single reservoir. This can help limit the impact of a water-quality problem or disease outbreak. Channels, tanks, equipment and pipework also require regular cleaning between crops.

Reliability is non-negotiable

NFT relies on continuous water movement, and plants have relatively little moisture reserve if nutrient flow stops. A pump failure, blocked pipe, electrical fault or low reservoir level can quickly become a serious crop problem, particularly during hot weather. Commercial systems need to be designed with failures in mind, with backup pumps, low-water alarms, equipment alerts, spare fittings and emergency power providing valuable protection.

The physical construction of the growing area is equally important. Channels need a consistent slope to maintain uniform water movement, as uneven or sagging sections can create areas where water pools or roots receive insufficient flow. A small design problem repeated across hundreds of channels could quickly become a much larger production issue.

Start with a commercial-scale pilot

The South Australian farm demonstrated that outdoor hydroponics can support substantial commercial leafy vegetable production, but it also showed that a successful system is about much more than the growing channels themselves.

Temporary support pots protect young plants during establishment, while raised benches, return infrastructure and protected pumping equipment support the recirculating system.

For a WA grower interested in this approach, a staged commercial-scale pilot would be a sensible starting point. Ideally, a trial would operate through both summer and winter using the farm's actual water source and intended varieties. Measurements could include marketable yield, crop duration, water and fertiliser use, labour requirements, electricity consumption, EC and pH stability, crop losses and production costs. These results could then be compared directly with existing field production.

For WA, the opportunity is not simply about growing vegetables without soil. It is about creating a production system in which water, nutrition and the root environment can be monitored and managed more precisely. That control is also the challenge: when water flow, nutrient concentration, temperature or equipment performance moves outside the required range, plants can respond quickly.

Outdoor NFT could have a place in WA leafy vegetable production, particularly where water efficiency, soil constraints or crop consistency provide a strong business case. The South Australian example provides practical ideas worth considering: protecting young plants during establishment, using gravity to assist water return, keeping key equipment under cover and positioning the return system and reservoir below ground to help protect the recirculating nutrient solution from environmental extremes.