How do microorganisms survive the cold? Do microbe numbers decrease each winter? Do I need to inoculate each year? We’ve gotten lots of these questions from our customers and we’ll try to address them in this week’s edition of Growing Possibilities.
Like other soil microorganisms, soil bacteria have a few adaptations to survive the colder months. One adaptation is the ability to slow their metabolic rate (energy they are using). Researchers have found that microbial metabolic rate changes with the seasons. During early fall, activity picks up due to increased nutrients left behind by plant material from harvest. The activity drops to stagnant yet stable rates during the cold months of winter (some soil bacteria are still found to be active low as -39OC!) until soils thaw once again in the spring and metabolism speeds up (1). Another adaptation that bacteria have is the ability to sporulate during stressful conditions. Microorganisms will release spores that can lie dormant during winter and will resume activity in the spring (2).
Are these adaptations enough to sustain healthy microbial counts for the spring? Not necessarily. Subzero temperatures have adverse effects on microbial overwinter survival and numbers (3). There may not be a high enough survival rate for reliable colonization of the rhizosphere in the following growing season (4).
Can anything be done to protect soil bacteria during winter? One method of increasing overwinter survival of bacteria is to use cover crops. Cover crops serve as a protective layer, decrease erosion, and foster a winter habitat of roots. The remaining biomass from cover crops can act as a carbon source in the spring, feeding soil microorganisms even when the primary crops are not actively growing (5). Another method of increasing microbial overwintering is no-till regenerative farming methods, resulting in higher root coverage and better survival rates (3). These methods can help to boost microbial activity in the spring-with having nutrients available sooner, leading to a jumpstart of the growing season (5).
Are these methods a reliable way to boost healthy microbial counts for the spring? Again, not necessarily. Researchers find that these methods produce mixed results, and still do not guarantee a high enough survival rate for colonization of the rhizosphere in the following growing season (1). Any way you want to cut it, subzero temperatures have adverse effects on microbial survival (3). While all these methods may be good sustainable practices, the only bullet proof way to increase microbial count in your soil is to add inoculants. XiteBio’s liquid inoculants (e.g. XiteBio® SoyRhizo® and XiteBio® PulseRhizo®) not only add desired rhizobia in optimum number, but our unique formulation technology (AGPT ®) also stimulate and galvanize native microflora (6).
If you would like to learn more on this subject, please contact one of our sales agronomists or give us a call at 1-855-XITEBIO. Until next time, we wish you healthier plants and better yields.
- https://www.sciencedirect.com/science/article/abs/pii/S0038071705002890
- https://pmc.ncbi.nlm.nih.gov/articles/PMC135340/
- https://www.sciencedirect.com/science/article/abs/pii/S1001074214002356
- https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/soils-fertility-and-nutrients/inoculation-of-pulse-crops#:~:text=However%2C%20bacteria%20that%20survive%20in,they%20plant%20a%20pulse%20crop.
- https://hpj.com/2023/12/07/what-happens-to-soil-microbes-during-the-winter-months/
- https://xitebio.ca/sustainable-technologies/