I am excited to welcome back Dr. Tuesday Simmons for the fourth "Tuesdays with Dr. Tuesday" monthly issue. Over the next few months, Dr. Simmons will share her perspective on the importance of the soil microbiome to agriculture and the development of new technologies.
You can read her full bio at the end of this post.
So far in this blog series, we’ve discussed basics of the soil microbiome, how plants interact with soil microbes, and the complexities of soil health. So how does this all connect with the practicalities of farming today? Farmers may recognize the importance of the soil microbiome, but it’s crucial for researchers and extension specialists to share new data on how farming practices can impact their underground allies.
In this article, we’ll dig into (no, I won’t stop using that pun) the impact of different management strategies (including tillage, cover cropping, crop rotation, and application of inputs) on the soil microbiome.
What “drives” the soil microbiome?
As soil microbiologists have sought to understand this “final frontier”, a major area of research is determining what variables might influence (or “drive”) the soil microbiome. For instance, in my PhD research, I investigated how drought can be a driver, pushing microbial communities in a specific direction.
The major drivers of the soil microbiome are: pH, climate, and organic carbon.
Not surprisingly, when you add in the complexity of crops growing in the soil and farmers cultivating them, there are a lot more variables that can drive the microbiome, primarily crop species and age (2).
Soil microbiologists have been working to understand the impact that farming practices have on microbial communities, and I’ve summarized some of their research here.
If you’re curious about how scientists determine what microbes are present in a soil, refer back to the first post in this series: Soil Microbes are Feeding the World.
Physical impacts: tillage
Like the other farming practices I’ll talk about, there are other resources that discuss the broader impact of tillage on soil quality, so here I’ll focus on the impacts to soil microbes.
Scientists have found that using conservation tillage practices increased soil carbon (total, active, and microbial biomass), but there’s no difference in microbial biodiversity between tilling and no-till systems (3). Despite no change in diversity, there are some differences in the types of microbes growing in the two different soils: nitrogen fixers are more abundant in no-till soils (3).
There is some evidence that a reduced tilling practice results in the most stable microbial communities over no-till or conventional till practices (4). A more stable microbiome can be beneficial because it resists the invasion of pathogens as well as bounces back more easily from disturbance.