Microbial abundance and community composition in topsoil profiles of differently cropped and fertilized arable soils

Soil microbial communities are crucial for ecological processes such as organic matter turnover and nitrogen cycling in agricultural soils. In the LOEWE project Green Dairy, we investigated the effects of two different cow manures from high- and low productivity feeding and crop rotatio on the soil microbiome in organic farming systems. Bulk soil samples of 0-10 and 10-30 cm depth collected in spring 2024 from eight arable plots were comparatively analyzed. Alfalfa (one and two year old), spelt, maize, potatoes, oats, rye, wheat and field beans were grown on the plots. Using quantitative PCR (qPCR), we determined the total abundance of bacteria, archaea and fungi as well as ammonium oxidizing bacteria and archaea (detected by amoA genes). In addition, we analyze the diversity and phylogenetic composition of bacterial and archaeal communities by 16S rRNA gene amplicon Illumina sequencing. Current results showed that the abundance of bacteria, archaea and amoA genes in bulk soil was effected by crops. Different manure types only affected the abundance of bacterial 16S rRNA and archaeal amoA genes. In general no significant differences were obtained among the two studied top soil layers. These findings underline the influence of crop rotation on the soil microbiome and thus on soil fertility and plant performance and provide important information for the sustainable management of agricultural land.