Study Shows Value of Soil Microbiome, Nurtured in Organic Farming, Harmed by Chemical-Intensive Ag

A study in the journal Biology and Fertility of Soils has confirmed once again that organic agriculture contributes significantly to soil health, improving ecological functions that are harmed by conventional, chemical-intensive farming practices. Organic soil amendments (fertilizers) that feed soil organisms increase beneficial protistan predators and support sustainable predator-prey relationships within the soil microbiome. [‘Protist’ is a catch-all term that describes ancient lineages of eukaryotes—organisms with a nucleus—that are neither a true plant, animal, or fungus.] The study shows that organic farming creates a healthy ecosystem able to support a balance of life forms in the soil. Moreover, the study finds that the use of chemical fertilizers for agricultural management disrupt the stable biological relationship between protistan predators and their bacterial prey in soils, adding to the argument for transitioning away from conventional systems that lean on toxic inputs.

Healthy soil contains millions of living species that form the microbiome. Most of the biodiversity in soil consists of bacteria and fungi, and their number and type are regulated partially by predatory protists and nematodes that feed on bacteria. Akin to the impact of predators keeping a herd of prey healthy by hunting the sick, protists keep the bacteria population healthy by removing the more inert microbes and releasing nutrients into the soil. In working together, these tiny organisms in organic land management systems determine the health of the soil for plant growth.

The authors indicate that they chose to examine protists because of the relative lack of studies regarding the effect of different fertilizers on the diversity and composition of soil protists, their importance to soil health, and their relative vulnerability to variations in agricultural practices. Compared with other microbial groups, researchers also cite evidence that protistan predators are more sensitive to the effects of petrochemical fertilizers. Fertilizers may cause changes in the diversity and taxonomic and functional compositions of soil protist communities.