By Robert N. Ames, PhD, Scientist Emeritus, Agricen Sciences
As previously mentioned, we can recognize stress on agricultural crops fairly easily based on poor growth, wilting or disease symptoms. However, we rarely consider stresses on the functioning of microorganisms in the soil – mostly because they can’t be easily seen, and we don’t really understand how most of these organisms function. We do know that the life cycle of individual soil microorganisms is short and may be only a few hours or days for many of them. So any disturbance of the soil will have an impact on the microbes present and their functioning within the microbial community.
Before we start looking at stresses to microbes, I think it will be helpful to better understand the concept of the microbial community. Most of us have been in an airplane at night and have seen the lights of the cities below. At a high elevation, the cities look like separate clusters of lights, but when we get lower, we can see that they are actually interconnected with roads, power lines and cell towers. There are brightly lighted areas of high activity and less-lighted areas of the countryside.
This is how I envision microbial communities in the soil. There are areas of the soil where the microorganisms are very active, especially near and around plant roots – and there are areas well away from the roots or sources of nutrients where the organisms are less active. So the microbial communities can be large or small, but they are constantly interacting and communicating. Also, as with us in our individual communities, soil microorganisms that make up the microbial community have thousands of different jobs, skills and services that they perform.
Stresses or impacts to the microbial community can occur with any type of soil disturbance. Even common agricultural practices such as cultivation, irrigation or fertilizer application induces a change or stress on the functioning of microbial communities to which they must adjust. This is much like a major road construction project causing you to take another route to work or slowing your ability to travel across town.
In the next blog post, I will outline the various components of microbial stress response to help us understand how the microbial community may respond to these changes.