Disease Control in Recirculating Hydroponic Applications

“Prior to installation of Silver Bullet’s water treatment system, we had intermittent occurrences of root issues. With Silver Bullet, we saw in increase in plant metabolism and root health we were not able to achieve with our previous water treatment program.”

The Customer’s Profile

Silver Bullet was introduced to a licensed commercial cannabis operation seeking to improve the water management program at one of their cultivation facilities. The owners have over 10 years experience employing drip irrigation and recirculating hydroponic growing methods across several commercial locations. The grower has earned a reputation as a high-quality and reliable producer, with long standing relations with several dispensaries in the San Francisco Bay area.

The facility utilizes reverse osmosis filtered irrigation water supplied to several indoor, controlled environment cultivation rooms. One half of the grow rooms use recirculating hydroponic growing methods, whereby plants are grown in soil-less media and supplied nutrient rich irrigation water at the optimum water pH, temperature and dissolved oxygen range for plant production. Prior to introduction of the Silver Bullet system, the grower had satisfactory production, but was eager to implement water treatment technology to improve business performance.

The Grower’s Water Management Needs

To maximize production efficiency and future profitability, the grower committed to upgrading the water management practices of the facility so that the following benefits could be achieved:

  • Continuous control of microbial growth so that water-borne diseases could be prevented

  • Compatibility with the existing nutrient fertilizer program

  • Replace the existing liquid chemistry treatment program

  • No plant phytotoxicity or impediment of plant growth

Silver Bullet Treatment Compared to Traditional Chemical Program

In collaboration with the grower, Silver Bullet developed a direct comparison demonstration between the Silver Bullet treatment system and the existing hypochlorous acid (chlorine hydroxide) chemical water treatment. The facility’s grow rooms were designed so that each room housed two discrete, recirculating hydroponic plant production systems that operate independently. The competing water treatment systems are in a single indoor, environmentally-controlled grow room allowing a side-by-side comparison while minimizing external variables.

The demonstration included a third-party laboratory monitoring program to compare and validate water quality and plant growth within both recirculating hydroponic systems. The program was designed so that the following performance metrics could be evaluated:

  • Bi-weekly bacterial analysis as an indicator for hydroponic disease control throughout the irrigation system

  • Monitor plant health throughout the crop cycle and compare post-harvest crop yield, plant quality and cannabinoid profiles

  • Monitor and record the safety, performance and reliability of both treatment programs

Silver Bullet’s Advanced Oxidation Solution

Silver Bullet installed its patented Advanced Oxidation Process (AOP) technology as a replacement to the existing chemical treatment program. Silver Bullet evaluated the size and hydraulic capacity of the recirculating hydroponic system, and the treatment solution was designed so that proper oxidant rates were applied to the irrigation water. Silver Bullet’s technology was installed with the recirculating irrigation loop using a customized, high-pressure injection system that allowed for optimal gas transfer and contact time. This treatment system was applied without altering the fertilizer nutrients, temperature, pH and dissolved oxygen of the water. The Silver Bullet technology also allowed the grower to maintain control of the water recirculation rate.

Root Pathogen Challenges Treatment Comparison

To minimize variables in the demonstration, both hydroponic systems began service at the same time using cloned plants derived from a single mother plant. After the initial weeks in veg production, all plants were manually transferred into the flower production room, where 50% were placed in a recirculating system treated with chlorine and 50% placed in a different recirculating system treated with Silver Bullet technology.

Figure 1: Both recirculating hydroponic systems in the final weeks of flower production. Plants treated with Silver Bullet are on the left.

After the initial weeks of the demonstration, poor plant health was observed in the system treated with chlorine. All plants within the chlorine-treated system showed severe signs of nutrient deficiency, stunted growth, wilting and browning of the leaves and plant tissue. Although several steps were taken to improve plant health, the chlorine treated system continued to deteriorate over several weeks.

In comparison, better plant health and growth rate in the Silver Bullet system resulted in improved plant size, canopy height, flower density/size, leaf size, root mass, and coloration (Figure 1). Both systems were operated for a full 8-week flowering cycle.

As part of the demonstration monitoring program, a state-certified laboratory specializing in microbial water analysis analyzed heterotrophic bacteria with Silver Bullet and the competing chlorine treated system. Results showed that the Silver Bullet system reduced bacterium in the irrigation water 85% compared to the chlorine-treated water. The results demonstrate Silver Bullet’s value proposition of biological growth control throughout recirculating irrigation systems to benefit plant production.

Results: Third-Party Validation Confirms Silver Bullet’s Success Resisting Plant Pathogens

After the respective plants treated by Silver Bullet and chlorine were harvested, Waypoint Analytical was contracted to perform water and plant tissue analysis on both systems to identify the source of the plant disease. Waypoint is a a nationwide, multi-location agricultural and environmental laboratory network. Silver Bullet worked directly with the laboratory’s plant pathogen division located in southern California, which examined the plant leaf, crown, roots and irrigation water from each of the recirculating systems.

Figure 2: Post harvest photo records showing the difference in root mass and stock diameter between the two systems. Again, roots provided with Silver Bullet treatment are on the left.

Waypoint Analytical Plant Testing Observations of Silver Bullet Plants

  • Samples tested negative for Fusarium

  • Sample leaves had significantly better color compared to the control plant leaves

  • A thicker main stem compared to the control plant stem

  • Larger diameter roots compared to control root structures

Waypoint Analytical Plant Testing Observations of Chlorine Treated Plants

  • Samples tested positive for Fusarium, which was identified within the vascular interior of the plant crown

  • Sample leaves had less than desirable color compared to Silver Bullet treated plants

  • Sample stem health and coloration was poor compared to Silver Bullet treated plants

  • Sample roots were discolored and less healthful than the roots from the Silver Bullet plants

In addition to the laboratory analysis, root biomass was calculated using the bulk weight of the plants from the two respective recirculating systems. The Silver Bullet treated plants showed, on average, 86% more root mass compared to the plants treated with wet chemistry (Figure 2). Plant size, canopy height, flower density/size, leaf size, root mass, and coloration were superior on the Silver Bullet treated plants in comparison to the chlorine.

Silver Bullet Earns Growers Trust

Throughout this demonstration, the grower was impressed with Silver Bullet’s treatment solution for hydroponic disease control, effectively mitigating the impact of a pathogen outbreak. The grower subsequently installed Silver Bullet technology on all the veg and flowering plant production operations throughout the cultivation facility.

In part due to the grower’s support, Silver Bullet is actively working with several industry consulting agencies and cultivators to expand the adoption of Silver Bullet’s treatment technology in similar applications.

If your business could benefit from improved water treatment methods, contact Silver Bullet Water Treatment for a complimentary evaluation of your water system.

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