101 Questions answered
How Strategic Tillage Impacts Soil Microbes: Short-term Loss, Long-term Gain
Yes, but any form of soil disturbance – even seeding – kills microbes, so it’s not as bad as it sounds. Soil life is constantly reproducing and dying due to changes in conditions such as soil moisture and temperature.
One-off or irregular tillage isn’t too bad. It tends to cause a temporary increase in microbial activity (by exposing previously protected organic matter so the soil life can have a bit of a feeding frenzy) followed by a drop in activity.
Microbes can recover, if given enough time and there is enough soil organic matter. Regular and intense tillage in low-organic soils can lower microbial populations over time. Microbes work harder to recover with each disturbance, using soil carbon in the process. Regular tillage also damages soil structure, meaning fewer pores for water, oxygen and roots and overall a less friendly place for soil microbes.
Practices that move soil carbon deeper into the soil like spading or inversion will also cause a drop in surface microbes as the microbes follow the carbon. If the soil is spaded or inverted, or topsoil is mixed or buried, the microbes get buried with it. This leads to microbes being more evenly distributed in the soil, rather than concentrated at the surface with the organic matter.
Tillage has the biggest impact on fungal hyphae because it breaks the hyphal networks (threads). This is bad for useful fungi like mycorrhizae which help crops take up water and nutrients, but good for pathogenic fungi like Rhizoctonia (and why tillage temporarily decreases Rhizoctonia). A single tillage event can cause a sudden crash in fungal biomass, but it will recover if tillage is not regular.
So, there is no need to worry that strategic tillage is obliterating your soil biology. In fact, if the strategic tillage is used to ameliorate other soil constraints, such as mixing lime into an acidic layer or burying water repellent soil, and creating a better environment for crop growth, it increases the chance of improving soil biology.
