Drought with high heat causes serious crop damage, but what about live soil microbes working away in the roots and rhizospheres? Will they survive the severe conditions experienced this summer?
Heat and moisture are two main factors impacting soil microflora. Will the microbes make it through our summer drought, then survive what might be another snow-less winter?
A weekly e-newsletter called Growing Possibilities, produced by XiteBio, recently delved into that concern. They looked at the question from the bacteria’s point of view.
Information presented here was gleaned from that e-newsletter.
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Soil moisture insulates against temperature change. Dry soil heats up faster as the weather turns hotter. Normal summer heat is unlikely to harm soil microflora. Soil microbes like a warm environment. Their growth and activity are encouraged by a little heat.
Beneficial soil bacteria increase their activity and respiration rates until soil temperature is slightly over 30 C. It appears helpful bacteria will actually thrive in the low 30 C temps we are expecting.
When soil temperatures approach 40 C, bacterial activity begins to decline. At 45 C their activity and respiration come to a near-standstill.
In a heat wave like the one this summer, the soil where microbes reside is unlikely to get hot enough to have a serious negative impact.
With dryness in cahoots with a heat wave, obtaining adequate moisture is a high priority for plants and microbes.
Manas Banerjee, chief executive officer and head researcher at XiteBio, says his company’s Plant Growth Promoting Bacteria (PGPR) may offer some help in hot dry conditions.
Banerjee explains that under stressful conditions, some PGPR products release a sticky substance that helps bacteria hold onto moisture and nutrients from adjacent soil. It prevents desiccation of bacteria and plant roots and increases soil aggregation to maintain a better water potential close to the plant.
PGPR helps plants find moisture by encouraging the development of root systems and root hairs. A well-developed root system is essential in combatting water deficiency. PGPR produce phytohormones to encourage early root hair and root system growth. This enhances their ability to find and uptake water later in the growing season.
In an email interview, Banerjee said, “PGPR bacteria has greater tolerance for environmental stresses, however, prolonged effects are hard to determine. We don’t know if our bacterium have been harmed by heat or flooding. Both native and applied microbes are affected similarly, and applied bacteria are not tagged.
“A farmer can obtain a base line of bacterial activity with lab tests to measure microbial biomass, enzyme activity, biolog plates, functional diversity and mineralization potential.”
Although hot summer temperatures usually don’t harm PGPR bacteria already in the ground, this is not the case for inoculants and biologicals still in their packaging. If an inoculant or biological product is still unopened, this does not mean it’s safe.
Inoculants and biologicals left outside where direct sunlight and ultraviolet rays can get to them, can be damaged and even rendered unusable. These living breathing bacteria require safe storage conditions to remain viable to colonise plant roots. Storage temperature should not exceed 28 C.
