Some turf professionals are hesitant to use microbial products on turf while using wetting agents, fungicides, grow lighting or when operating in extreme heat, salt or drought environments because they fear products containing microbes will not benefit them. However, there is plenty of proof that an abundance of active, diverse, beneficial microorganisms in the soil is critical for healthy turf that can withstand stress.
How do microorganisms cope with extreme conditions?
Do microbes survive the environmental and maintenance stress on soccer pitches and golf courses?
What about storage and shelf life?
What are the microbe's strategies to survive?
What are practical steps you can take during storage and the application of products to ensure the microbes survival and best performance?
Microbes are highly specialised in the most hostile environments on this planet. Even if they are not in ideal conditions, they can often survive as dormant, inactive permanent forms. Here are some exciting examples!
Some microbes are adapted to toxic chemical environments like high salinity. Halophile (salt loving) microbes can live in environments saturated with salt, like the death sea. They pump out excess salt ions to maintain osmotic balance. The fermentation of salty foods such as soy sauce, salted cod, sauerkraut, etc. often involves halophiles as essential ingredients.
Halophile, salt loving microbes in Sauerkraut (Adobe Stock)
A thermophile is an organism that thrives at relatively high temperatures, between 40 and 120 °C. Some of them are bacteria and fungi. Thermophiles are found in hot springs and deep-sea hydrothermal vents, and in decaying plant matter, such as in a compost box in your backyard. Those organisms can survive in a wide range of temperatures. As an example, Geobacillus bacteria have been isolated from cool soils and even extremely cold ocean sediments in very high numbers, which is very surprising, given that the ambient temperatures are significantly below their minimum requirement for growth. Geobacilli are active in environments such as hot plant composts (Zeigler, Daniel R. (January 2014). "The Geobacillus paradox: why is a thermophilic bacterial genus so prevalent on a mesophilic planet?". Microbiology. 160 (Pt 1): 1–11)
Some microbes perform well in icy environments like glaciers and permafrost. They produce antifreeze proteins that prevent ice crystal formation, allowing them to remain active at temperatures as low as -20°C. Some pathogenic bacteria can even survive and thrive in frozen food in your freezer (Chattopadhyay, M. K. (2006). "Mechanism of bacterial adaptation to low temperature". Journal of Biosciences. 31 (1): 157–165).
Most bacteria are Mesophiles, they prefer moderate temperatures around 30-40°C. Most of them can enter a dormant state, forming spores with tough outer shells, to survive periods of extreme heat or cold.
Microbial packages of bacteria and/or fungi in our products such as TourTurf® Organic Green & Pitch, TourTurf® Thatch-Less® FTD Fungi Thatch Degrader or TourTurf® BAP Bacteria Activo Plus contain them in high numbers.
For example, BAP contains 200,000,000 colony forming units of Bacillus bacteria in each millilitre of product. We always try to exceed the guaranteed number of microorganisms during formulation to ensure the guaranteed amount is still available after the ‘use before date’. During the production process, the temperature is monitored carefully when adding the microbial blends to make sure we keep well below the threshold for the tolerance of the bacillus, Trichoderma and mycorrhizae.
To learn about the numerous benefits, they provide for plants and the soil, please read the article “The Multiple Advantages of Applying TourTurf® Microbes to Turf”.
The shelf life of microbial products is determined by the type of carrier material used.
Liquid products containing Bacillus spores have a guaranteed shelf life of 24 months when unopened. Once the product is opened, it must be used as soon as possible.
Granular fertilisers containing microbial packages of Bacillus spores, Gram positive and Gram-negative non-spore forming bacteria and fungal spores have a guaranteed minimum shelf life of 12 months. Granular fertilisers should be stored cool and dry.
In general, use products containing microbes as soon as possible, if possible, in the same season you purchase them.
Because of their small size, microbes are particularly sensitive to the effects of UV because of a high surface area-to-volume ratio. They lack a UV shielded germline, a trait that gives multicellular organisms some protection against the effects of UV. Bacteria do have several repair pathways that respond to UV-induced damage. But for many species, even brief exposure to direct sunlight is lethal. Wild type bacteria are often quite resilient to UV. Some bacteria have a specific response to UV exposure that can be turned on and off (https://www.nature.com/articles/s41545-020-0057-7).
Dormant spores of the various Bacillus species, including B. subtilis, are 5 to 50 times more resistant to UV radiation than are the corresponding growing cells (https://pubmed.ncbi.nlm.nih.gov/11746741/).
Melanin, carotenoids and mycosporines are the three major pigments that are well documented in fungi and act as sunscreens or antioxidants to minimize the damage generated from UV exposure (Almeida-Paes et al., 2012b; Avalos and Limón, 2015; Belozerskaya et al., 2017; Volkmann et al., 2003).
It was demonstrated that transcription of cellulase genes increased during growth on cellulose in constant light compared to constant darkness (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2954361/). Certain mutants of Trichoderma spp. have been reported to have better rhizosphere competence compared to their parent strains (https://www.researchgate.net/publication/371486920_Exposure_of_Trichoderma_isolates_to_different_doses_of_UV_radiation_for_development_of_mutants_and_their_stability_in_subsequent_generations).
UV is lethal (depending on wavelength and exposure), but microbes have strategies not just for countering the negative effects but harnessing mechanisms to benefit from it.
To ensure the best performance of microorganisms, try to get them into the root zone as fast as possible. It might help to open the root zone by using any means of aerification. Use the irrigation system to water in the product. When applying liquid products, add a penetrant like TourTurf® EPT Respond® Extreme Penetrator to improve soil penetration and apply the product with a higher application rate of water and use bigger nozzles to apply them where they belong, in the soil.
UVC light destroys the DNA of actively growing pathogenic fungi and seems to be a promising tool in integrated disease management, allowing to reduce the use of fungicides. More and more devices from different manufactures are available to treat turf. According to one leading manufacturer: “The effectiveness of UVC treatment depends on its spectrum and dosage. ... When biological organisms are exposed to UVC light within the range of 200 nm to 280 nm, the light penetrates their cell walls and disrupts the DNA molecules” (https://sglsystem.com/products/sustainable-grass-disease-management/the-uvc180/). Those devices cannot selectively protect beneficial bacteria and fungi.
Therefore, you could reapply microbial products after UVC treatment. Use aerification, big droplets, high water volume and penetrants to apply microbial products into the soil where they are protected from natural and artificial UV light including UVC treatment.
From the data available, that's not always the case. Beneficial soil fungi might be more susceptible to damage than bacteria. There are some studies that have reported synergistic effects from the application of bacteria from the genus Bacillus, when applied in combination with some synthetic pesticides. For example, Peng and co-workers studied a possible synergistic effect of B. subtilis NJ-18 with flutolanil and difenoconazole fungicides. The obtained results showed that, when combined, the agents demonstrated superior control of wheat sharp eyespot caused by Rhizoctonia cerealis (Peng, Di & Shandong, Li & Chen, Changjun & Zhou, Mingguo. (2013). Combined Application of Bacillus subtilis NJ-18 with Fungicides for Control of Sharp Eyespot of Wheat. Biological Control. 70).
Other studies in agricultural soil indicated that even low pesticidal concentrations may cause tremendous shifts in chemical and biological soil properties, biochemical activity, and soil microorganisms (Cycoń et al., International Biodeterioration & Biodegradation, Volume 64, Issue 4, 2010, Pages 316-323, ISSN 0964-8305).
It is best practice to use as little fungicides and pesticides as possible to avoid negatively influencing the microbial community in the soil. If fungicide applications are unavoidable, continue to reapply products containing TourTurf® microbial packages to reintroduce and increase the count of beneficial soil microbes a few days after any fungicide application.
When testing the effects of our new organic TourTurf® REO Respond® Extreme Organic Wetting Agent on soil microorganisms, the amount of soil microorganisms increased, presumably because of the optimized soil moisture levels throughout the season.
Read the article describing this effect here: Wetting Agent & Biostimulant approved for organic farming.
TourTurf® REO
Even conventional wetting agents like TourTurf® ELL Respond® Extreme Long Lasting will not reduce the amount of soil microorganisms according to internal trials.
Microorganisms are highly specialised to even the most extreme environments
Because of artificial turf rootzones and maintenance practices, the environmental conditions for soil microorganisms are not always ideal.
Most beneficial soil microorganisms prefer moderate warm temperatures, moist but not wet conditions and depend on oxygen
If conditions are not ideal, they can often survive as dormant, inactive permanent forms
Apply products, containing soil microbial packages, directly to the soil to avoid UV exposure
Keep the soil at optimal moisture levels, well aerated and limit pesticide applications to the absolute minimum
Reapply beneficial soil bacteria and fungi regularly to keep up high levels