Biodiversity of soil microbial communities in conventional and organic agriculture in Southern Sweden

Soil microorganisms in agricultural fields are an important contributor to soil nutrient cycling. The soil microorganism abundance and diversity are affected by multiple factors, including physical and chemical soil characteristics as well as agricultural farming practices, all of which combine to affect crop growth and crop yield. As organic farming bans the use of synthetic chemical inputs, inducing changes in soil tillage and fertilization types, we expect positive effects on the soil microbial communities compared to conventional farming systems. To test this, soils from 30 farms of both conventional and organic systems were sampled, including small grain cereals (annual crops) and leys (improved sown grassland - perennial crops). Soil chips inoculated with these soils were used to determine microscopically the abundance of different microorganism groups. This was followed by conducting molecular identification of microbial diversity (bacteria, fungi and protists) for fresh soils, lab incubated soils and internal parts of the soil chips. Results showed variable abundances across the microbial groups for both crop types and the agricultural systems. Preliminary molecular results of fresh soils indicate comparable genetic diversity within and between crops and farming systems. Molecular results were compared to soil chip samples resulting in rather small microbial community shifts for lab incubated soils, but with stronger shifts in internal parts of the soil chip. Our results show that microbial group abundances via soil chip microscopy vary for crop type and farming practices, indicating possible effects by specific field treatments. On the other hand, preliminary molecular microbial biodiversity results show comparable microbial diversities for the fresh sampled soils, indicating a rather stable microbial diversity in agricultural soils.