Effect of long-term mineral fertilisation on soil microbial abundance, community structure and diversity in a Typic Hapludoll under intensive farming systems

Abstract

Fertilizer application can influence not only plant communities, but also the soil microbial community, and consequently soil quality. Mineral fertilization can directly or indirectly affect the soil chemical properties, microbial abundance, the structure of the soil microbial community and diversity. We investigated the impact of the following six different mineral fertilizer regimes in a maize/soybean rotation system: control (CK, without fertilization), PS (application of phosphorus plus sulphur), NS (application of nitrogen plus S), NP (application of N plus P), NPS (application of N, P plus S), and NPSm (application of N, P, S plus micronutrients). Soil samples were collected during the physiological maturity stage of maize and soybean in march of 2013 and 2014, respectively. Overall, mineral fertilization resulted in a significantly decreased soil pH and an increased total organic carbon (TOC) compared to the CK. In addition, the analysis of terminal restriction fragment length polymorphism (T-RFLP) revealed that fertilizers caused a shift in the composition of both bacterial and fungal communities. In the 2013 season, the highest value of Shannon diversity of bacterial terminal restriction fragments was registered under CK. In the 2014 season, NPSm showed the lowest values of diversity for both bacterial and fungal TRFs. Considering both crop growing seasons, the analysis of phospholipid fatty acid (PLFA) detected the lowest value of total PLFAs under CK, suggesting that fertilization increased total microbial biomass. Furthermore, the bacterial and fungal abundance were examined using a real time polymerase chain reaction (qPCR). Overall, the results revealed that mineral fertilization led to decreased bacterial abundance (16S rRNA), while fungal abundance (18S rRNA) was found to be increased in both crop growing seasons. Our results show that mineral fertilizer application has a significant impact on soil properties, bacterial and fungal abundance and microbial diversity. However, further studies need to be carried out to obtain a better understand the mechanisms involved in the changes of microbial communities as a consequence of the application of fertilizers.