Maintaining water culture systems

Hydroponic production systems can be very attractive. Their productivity and efficiency are a few of the qualities that draw people to them.

However, although their high-tech appearance and automated features give the impression these systems are low maintenance, that is certainly not the case. These systems are not crock pots where you can “set it and forget it;” rather, maintenance is required to keep them operating smoothly.

This article focuses on some of the routine maintenance required to keep water culture systems like nutrient-film technique (NFT) and deep-water culture (DWC) functioning their best year-round.

Focus on filters

Filters are commonly used to help keep particulates out of the nutrient solution. While loose organic substrates such as ground coconut coir and sphagnum peat moss used for hydroponic production are stabilized either chemically with a binder or physically with a spun-bound fabric or paper fiber wrapper, particles still come loose and get into the nutrient solution.

Even inorganic substrates including phenolic foam, which are stabilized by nature, can still sluff off particulates into the nutrient solution. Other organic debris, like dead root tissue and algae particles, can also build up and cause problems. Regular maintenance on your filter system will ensure consistent flow of nutrient solution throughout your system. This is especially important for in-line filters just before headers to microtubing. Failure to maintain filters not only slows or ultimately stops flows, but can also allow particulates to get into the system and clog lines (Fig. 1).

Clean those rafts and channels

Regardless of which system you are using, regular cleaning and maintenance of NFT channels and DWC rafts is essential. Each harvest is an opportunity to clean channels and rafts in good working condition, as well as sanitize them to reduce pathogens that are problematic to plant growth or human health. For NFT channels, inspect them for any damage that may be contributing to leaks. If the channels have end caps on them, make sure they are thoroughly attached; if not, set them aside to dry and reapply the adhesive you are using. While not the channel per se, taking time to inspect the microtubing and associate plumbing for NFT channels is useful. Make sure tubes are properly inserted into grommets, and that grommets are still on DWC rafts, inspect the polystyrene to ensure its integrity; cracks in the tray not only make them weaker and prone to breakage, but also serve as a place for algae to grow and establish.

In order to effectively sanitize rafts and channels, be sure to clean them first, then follow-up with a sanitizer. Regardless of which cleaners and sanitizers you are using, always make sure they are food grade and that you follow the manufacturers’ instructions. This will help ensure they are effective and safe. On a smaller scale, most raft and channel cleaning and sanitizing takes place by hand. Automation can help reduce the amount of labor it takes to clean and sanitize rafts (Fig. 2) and channels and, while it is most often used for large-scale operations, small-scale solutions are definitely possible (think: cleaning brush in an electric drill).

Reservoirs require periodic cleaning, too

Nutrient solution reservoirs also need to be kept as clean as possible to stop the spread of any unwanted plant or human pathogens and algae throughout production systems.

The best time to clean your nutrient reservoir is when systems are being flushed and nutrient solutions exchanged for fresh solution. Although nutrient solution exchanges are often done on a calendar basis, such as every three to four weeks, it is preferable to do it on an as-needed basis based on nutrient solution tests showing imbalances in nutrient concentrations or insufficient or excessive concentrations of nutrients. Taking this approach, you may find 100% exchanges are not occurring as often, reducing the opportunity to have an empty reservoir.

For algae management, treat the nutrient solution like a sump for fan-and-pad cooling. Keep it shaded to minimize sunlight reaching the tank to minimize algae growth; if possible, place it in the ground for maximize light blockage.

Biofilm is another issue hydroponic producers must contend with. Allowing biofilm to develop can increase the likelihood of plant and human pathogens building up in a system. Although periodic shock treatments to systems can help clean biofilm, a regular maintenance program can help keep it in check. There is already a good chance the techniques used to control biofilm are already being used to keep the health of hydroponic systems in check.

Ultraviolet (UV) sterilization is an effective practice and is also used for plant and human pathogens. Peracids, such as hydrogen peroxide products, are also effective for maintenance treatments. To maximize the effectiveness of these treatments, properly functioning filters help reduce particulates that can otherwise reduce their effectiveness in suppressing biofilms.

The practices outlined in this article are steps you can take each week to keep NFT and DWC systems operating smoothly and successfully. By paying attention to small details, you can avoid big problems in production.

Christopher (ccurrey@iastate.edu) is an associate professor in the Department of Horticulture at Iowa State University.