18 Sep Biologicals & Winter Crops: Can Bacteria Survive the Cold?
While many farmers have been busy logging long hours on the combine this fall, some have also started rolling out their planters. Winter wheat & winter peas are examples of winter crops that are becoming increasingly attractive and profitable for producers. Improvements in seed genetics and agronomic practices have led to higher yields, but are inoculants and biologicals an option as well? Can growth-promoting bacteria remain viable and survive the winter? The answer is YES!
Soil bacteria live and travel in water film found throughout the soil (1). As winter and colder temperatures arrive, the soil and the water within will begin to freeze. However, similar to a river, the water in the soil does not freeze all at once. When temperatures get cold enough and water in the soil begins to freeze, the natural salts in the water move from the frozen water into the remaining liquid water and give it a higher salt content (2). This lowers the freezing point of the water, keeping it as a liquid and providing bacteria an environment in which to live.
And live they do! Even during the winter, soil bacteria have been found to be active, though their level of activity can slow down as temperatures drop (3). Similar to how water can naturally develop a lower freezing point, bacteria can produce antifreeze compounds that help them survive a colder environment, even down to -39°C (4). Obviously, not all bacteria will survive, some can tolerate more than others, some may even produce spores to protect themselves from the uncongenial weather.
Just as inoculants and biologicals enhance crop yields during the summer, they could be an option for winter crops as well. XiteBio® PulseRhizo® inoculant for winter peas and XiteBio® Yield+ biological for winter cereals are two examples of plant growth promoting rhizobacteria (PGPR) that perhaps can help improve your winter crop performance. Don’t let your yields be frozen!
1) Oquist M.G., et al. (2009.) Water availability controls microbial temperature responses in frozen soil CO2 production. Glob Change Biol 15:2715–2722. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2009.01898.x
2) Harrysson Drotz S., et al. (2009). Contributions of matric and osmotic potentials to the unfrozen water content of frozen soils. Geoderma 148:392–398. https://www.sciencedirect.com/science/article/abs/pii/S0016706108003212?via%3Dihub
3) Nedwell D.B. (1999). Effect of low temperature on microbial growth: Lowered affinity for substrates limits growth at low temperature. FEMS Microbiol Ecol 30:101–111. https://academic.oup.com/femsec/article/30/2/101/608571
4) Panikov N.S., Flanagan P.W., Oechel W.C., Mastepanov M.A., Christensen T.R. (2006). Microbial activity in soils frozen to below -39 degrees C. Soil Biol Biochem 38:785–794. https://www.sciencedirect.com/science/article/abs/pii/S0038071705002890