Importance of fungi in a 63 years old long-term field experiment with 20 years of maize growth

Highlights

• Long-term N fertilization did not affect the microbial abundance.

• Fungi to bacteria ratio were up to 5.9 in the rhizosphere and 2.8 in bulk soil.

• δ¹³C values showed fungi to be the most active group in the rhizosphere.

Abstract

Microbial diversity and their activity in the rhizosphere and bulk soil areas were measured in a long-term field trial (started in 1956), where maize has been grown for the last 20 years with and without N fertilisation. Various microbial groups and their substrate feeding strategies (i.e. demonstrating activities) were identified through phospholipid fatty acids (PLFAs) analysis and their δ¹³C values. Microbial abundance (esp. fungi) remained unaffected by long-term N fertilisation. However, fungi dominated over bacteria with 2–3 times higher biomass in the rhizosphere than bulk soil. The δ¹³C of PLFAs showed that fungi had the highest values, particularly in fertilised rhizosphere areas, indicating that this was the most active group (than any other microbial group) for assimilation of maize rhizodeposits.