The Future of Hydroponic Crop Production: The Membrane Menis

Did you know that hydroponic cultivation dates back to the ancient time of Babylon? Today, modern technology has given us thousands of types of different hydroponic system designs around the world, and not one of them is perfect.

It’s widely accepted that stonewool slab culture and coco-based media are both commercially-viable hydroponic methods, while deep water culture, nutrient film technique and aeroponics can yield incredibly fast growth.

However, all current hydroponic systems out there have serious limitations and the potential for failure. I’ve recently been introduced to an innovative hydroponic system design, a system that I believe has the potential to drastically change the way we view hobby and commercial crop production.

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So where did this exciting idea come from? The Hydroponic Gardening Society of Victoria introduced me to the concept. The society is a lovely group of extremely enthusiastic horticulturalists. Members meet monthly to showcase their beautiful gardens, share seeds and experiences, and discuss hydroponics over tea and biscuits.

Andrew Parker is one of the society’s esteemed members and is a qualified research engineer in the field of mechanical design and development. He recently published a 192-page e-book (The New Hydroponics, 2014) that comprehensively details this system design and provides a thorough investigation into hydroponic cultivation. The results from his years of commitment to ongoing trials are astounding.

The method Andrew outlines in his book is a revolutionary, yet very simplistic concept. It’s called the membrane meniscus method and it doesn’t require a growing medium, air or water pumps. Using this method of hydroponic plant production, plants can achieve phenomenal growth rates at incredibly high densities. The membrane method can easily produce more than 600 spring onions in just one square meter.

How Does the Hydroponic Membrane Meniscus System Work?

The membrane meniscus design uses an extremely slow inlet that drips into a mat at the base of a tray. The nutrient solution flows slowly through the buffer mat and drips out the other side of the tray. As the buffer mat absorbs the moisture, the nutrient solution flows vertically upward through the wicking action of the roots. The roots grow directly on top of a fabric membrane above the buffer mat and develop into a thick root mass.

The top of the tray is covered with a lightproof plastic sheet with openings for the stems. The plant shoots flourish above the plastic while the root system develops extremely happily in the dark. As the root tips develop across the fabric, the thin liquid film surrounding the roots draws nutrients upwards by capillary action. Incredibly, the plant roots grow in fresh air! Through the natural process of diffusion, plants receive an abundant amount of oxygen, and the slow drip is sufficient to ensure nutrients are constantly refreshed and can be efficiently absorbed.

This new, distinctive approach to hydroponic cultivation requires only gravity to provide ample flow to the drip inlet, and the negligible outflow can be easily captured and recycled. Without the need for air or water pumps, the membrane method also removes the potential for mechanical failure, ensuring the systems are extremely low maintenance.

Although gravity is generally sufficient, depending on your crop arrangement for commercial or larger hobby systems, a small water pump may be necessary to ensure the slow drip flow is ample. For all intents and purposes, the membrane meniscus method can be described as powerless because a single, small solar panel can be used to feed hundreds of thirsty plants.

By using the root system as the wicking mechanism, growers are able to plant at significantly higher densities than previously trialed and the results are extremely promising. Even large, heavily fruiting or flowering crops such as tomatoes and cucumbers can be effectively cultivated with minimal upfront costs. The design is so adaptable that plants can be grown in either a sea of green or a screen of green approach with astonishing results.

Aside from its practicality, it is the science behind this clever method that really impresses me. Unlike NFT or DWC systems, additional aeration in a reservoir is not required for the membrane meniscus method, and the extremely thin layer of liquid surrounding the roots provides a consistent supply of nutrients and oxygen.

A meniscus forms this essential coating of water. If you can remember back to your high school science class, the meniscus is the curve in the upper part of a liquid that is caused by surface tension. As liquid depth decreases, the rate of diffusion providing dissolved oxygen increases, so this thin liquid film provides a perfectly aerated water supply.

As the root mass develops into a thick mat and the turnover rate is high, additional nutriment is naturally provided to the plant. This moisture turnover rate is crucial to the absorption and distribution of oxygen in the root zone.

As dissolved oxygen implicitly affects most plant functions, including respiration, transpiration and photosynthesis, it is imperative that growers maintain a healthy, robust, oxygen-rich root system. Healthy roots are more capable of resisting pathogens and improving the overall health of a plant, so they need to be carefully monitored by farmers. Unfortunately with many traditional hydroponic techniques, examining and maintaining the root zone can be quite difficult.

One of the most attractive features of the membrane meniscus method is its practicality and ease of use for both hobby and commercial growers. With its simplistic and accessible design, it allows for easy routine inspections, adjustments and cleaning. The ongoing maintenance is as simple as ensuring the drip-feed doesn’t clog and keeping up with quick visual checks that cover the entire plant system.

Another interesting characteristic of the membrane method is the layer of fabric between the buffer mat and the membrane. Traditional hydroponic systems encourage the roots to be in direct contact with the nutrient solution. This allows the root exudates (the secretions and mucilage excreted from the root surface) to influence and contaminate the nutrient solution.

By providing a layer between the roots and the nutriment, the solution remains more stable and balanced, and the plant is able to absorb mineral nutrients more economically. For hobby systems, this sub-layer is generally an optional addition as the diffusion between the root zone and the nutrient supply zone is too small to be significant in the clever membrane design.

This leads us into the really juicy bit: how the membrane method saves you serious money. Current trials have found that hydroponic-specific A/B nutrients work beautifully with the meniscus model. Amazingly, the membrane method has the potential to use significantly fewer mineral nutrients while still increasing yields. It’s accepted that dissolved oxygen is essential for the efficient uptake of nutrient elements, and in the membrane system, the oxygen is continually dissolved in the solution and replenished as it is consumed.

This highly saturated oxygenation allows for more rapid nutrient uptake, which means your plants will actually thrive at a much lower EC. In commercial hydroponics, the farmer aims to find an acceptable range of elemental concentration, balancing the cost vs. return of mineral nutriment supply alongside the relevant environmental conditions. This design has the potential to drastically reduce our mineral fertilizer use and lower our overall horticultural industry’s environmental footprint.

So, while saving money on upfront costs, electricity and hydroponic nutrient supplies, you can also grow some genuinely environmentally friendly and delicious fruits and vegetables using the membrane meniscus method.

For those innovative and industrious hydroponic enthusiasts who want to experiment with this method (you can expect some monster yields), simply find a copy of the e-book I mentioned earlier. It’s comprehensive and extremely helpful. It’s also worth noting that it’s only the very early days of this discovery and that further research is always essential to fine-tune any horticulture system.

Andrew is preparing his next publication with a focus on increased crop densities, module and channel assembly, and large-scale commercial production systems. His current trials have exceeded 100 kg per square meter per year for tomatoes with basic environmental control, and all other crop yields have exceeded industry standards.

My own membrane method chilli trials at home are thriving, and I’m continually learning about how my plants and the system interact. The practical tips I’ve discovered when designing my own membrane system are largely related to the external growth factors surrounding the system.

Always remember that temperature influences dissolved oxygen levels in an aqueous solution, so ensure your tray and reservoirs are located accordingly. And, as with any other hydroponic system, to prevent algae and pathogenic problems, always look out for light leaks and make sure your plumbing is tidy and effective. Measure twice, cut once!