Soil resident microbes are resilient to long-term fertilizer application

Synthetic fertilizers are part of agriculture since almost 100 years after the discovery of the Haber-Bosch process and about 50% of the current agricultural production relies on this process. Little is known how long-term application of synthetic fertilizers impacts the homeostasis of soil-resident microbial communities, a key parameter of “soil health”.

New work from a team of scientists headed by Paul Schulze-Lefert at the Max Planck Institute for Plant Breeding Research in Cologne, Germany, provides first insights on the impact of long-term application of synthetic phosphate fertilizer on soil ecology and root-associated microbial communities in an agriculturally relevant setting using soils originating from a long-term field experiment at the Martin Luther University Halle-Wittenberg.

The authors demonstrate that the soil-resident bacteria and fungi are highly resilient to persistent perturbation by synthetic phosphate fertilizer applied over more than 60 years. The most significant effect of phosphate application is observed inside the plant roots, demonstrating that plants grown in soils with contrasting phosphate availability have slight, but significant differences to their root-colonizing microbial community composition. The change in fungal root-associated consortia is more than double compared to bacterial assemblages, which may indicate a preference toward root colonization of soil-resident fungi in soils with reduced phosphate availability.

It is remarkable that a major perturbation in soil ecology could not be observed after an extended period of synthetic fertilizer application and thus the impact of fertilizer on soil health appears to be marginal. At this stage, detrimental effects of synthetic fertilizers are limited to cases of excessive application, resulting in leaching into the (aquatic) environment.