Vertical farming—growing systems involving soilless mediums in stacked, highly controlled indoor environments—has boomed over the past decade.
By utilizing indoor spaces and advanced technologies, vertical farms offer numerous advantages, including localized food sys
tems, reduced water consumption, and resiliency against the extreme weather events currently threatening most of the planet’s major growing regions.
Despite the potential of these systems, many vertical farms face significant challenges in establishing long-term economic viability. To justify the significant outlays needed for growing equipment, energy supply, and building space, vertical farms must achieve optimal productivity. To do so, vertical farms need to be based on safe crop production systems that are extremely resilient to crop-destroying pathogens and other biological threats.
The Food Safety Challenges of Vertical Farming
Commercial vertical farming operations usually employ soilless growing systems like hydroponics or aeroponics. A nutrient solution cycles throughout the entire system to significantly improve the water and fertilizer efficiency of hydroponic farms. But the efficiency of closed-loop systems also creates considerable food safety challenges for growers.
The efficient transport and re-use of a nutrient solution can unintentionally facilitate the rapid spread and growth of disease and pathogens. This can quickly destroy entire crops or render them unsaleable due to food safety concerns. The attempt to procure a sterile, controlled environment designed to avoid these outbreaks can quickly become a detriment, as pathogens can spread rapidly in the absence of the moderating influence of diverse microbial ecosystems that exist in traditional soil-based growing systems. Pathogens can be introduced via improperly washed processing equipment, propagation tools, irrigation water, and the hands of farm workers, and by neglecting to inspect purchased plants before they enter the facility.
Pathogens and disease can throw the economic viability of vertical farms to the wind. In a game of such tight margins, vertical farmers continue to experiment with underutilized strategies for improving farm biosecurity, including introducing microbial inoculants into their growing systems.
Microbial Inoculants and Vertical Farming
The use of microbial inoculants in vertical farming environments is done with a focus on their plant growth and yield-boosting benefits. But the greatest potential for these products may lie in their ability to mitigate major biosecurity threats to crop success. This includes plant pathogens and the buildup of toxic root exudates.
The indoor, controlled environments of vertical farms naturally minimize the quantity and variety of pests and pathogens that field-based crops must contend with. However, the closed-loop hydroponics systems—where nutrients and water continuously cycle throughout the system—are not immune to damaging pathogenic outbreaks.
If filtration systems and sanitation protocols are not optimized, pathogens can rapidly proliferate and spread through an entire vertical farm far faster and more efficiently than they would in soil-based crops. Consistently high ambient temperatures, high humidity, nutrient-rich solutions, and close plant spacing may also create environments in which plant pathogens can thrive.
A well-managed vertical farm will minimize disease risk, but the complete exclusion of pathogens from these controlled growing environments is essentially impossible. Certain microbial species, including several Bacillus strains, can further mitigate outbreaks. These microbes suppress plant diseases by producing phytohormones and antimicrobial compounds that can lower populations of plant pathogenic microbes such as bacteria and fungi. Microbial inoculants containing Bacillus species can help control Pythium spp., Cryptococcus coccoides, Fusarium oxysporum, and Rhizoctonia solani in popular vertically farmed crops like tomatoes and salad greens.
Ultimately, microbial life will colonize vertically farmed plants—whether you add beneficial microbes or not. So, filling the free real estate with plant-benefiting bugs early on is one-way growers can mitigate pathogen colonization.
Toxic Root Exudate Buildup
The closed-loop nature of vertical farming systems creates other challenges too, namely the accumulation of potentially harmful organic compounds released through plant roots. The buildup of these toxic root exudates can lead to autotoxicity, a phenomenon in which “a plant species releases chemical substances which inhibit or delay germination and/or growth of the same plant species.”
Avoiding autotoxicity in vertical farms requires the implementation of removal strategies. The challenge is removing accumulated root exudates without interfering with the nutrient composition of the aqueous solution cycling through the system. Physical and chemical techniques, like ozonation, activated carbon adsorption, TiO2 photocatalysis, and membrane filtration, are typically required to degrade or remove these compounds while maximizing the useful lifespan of the nutrient solution.
In addition to these techniques, introducing beneficial microbes via inoculations can help mitigate autotoxicity. Certain microbial species degrade phytotoxins that can eventually inhibit plant growth if left untreated.
Using Microbial Inoculants in Vertical Farms
In many ways, the closed-loop, highly controlled growing systems found in vertical farms represent the ideal environment for testing the efficacy of microbial inoculants. The plant growth-promoting benefits of beneficial microbes in vertical farming systems are well documented—many indoor growers already use microbes to reduce fertilizer use while sustaining and improving yields.
Beyond plant growth benefits, the role microbial inoculants can play in improving food safety and saleable yields by mitigating biotic stresses remains understudied, but current research suggests promise here as well. Many plant growth-promoting microorganisms (PGPM) found in high-quality inoculants may also prevent or significantly reduce the negative impacts of Fusarium, Phytophthora, and Pythium—the most common plant pathogens threatening vertical farming systems.
Large upfront infrastructure investments and the ongoing energy demands of artificial lighting mean that the margin of error for vertical farms is extremely tight. Microbial inoculants present a low-risk and potentially high-reward strategy to improve yields and mitigate pathogenic outbreaks—ultimately improving the long-term economic viability of vertical farms.
Getting Started with Microbial Inoculants
Microbial inoculants like Impello’s Continuμm™ can be added to aqueous nutrient solutions in vertical farming systems, from seeding right through harvest. The consortium of Bacillus and Paenibacillus bacterial strains found in Continuμm™ can enhance plant growth while improving plant resilience to common biotic stresses found in vertical farming systems.
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