Long-term No-Tillage and Different Residue Amounts Alter Soil Microbial Community Composition and Increase the Risk of Maize Root Rot in Northeast China

Conservation agriculture practices, such as no-tillage and crop residue retention, are proposed as sustainable soil management practices. However, it remains unclear how long-term no-tillage and residue retention affect microbial community composition and soil-borne plant pathogen abundances. This study investigated the impact of long-term (10 years) no-tillage with different mulching amounts (0%, 33%, 67% and 100% of 7.5 t/ha maize straw) on soil microbial community composition and abundances of two pathogenic fungi (Fusariurn graminearum and Pusan= monWonne) during the maize growing season in northeast China. We explored the changes of soil microbial community and pathogenic fungi abundance by Illumina MiSeq sequencing and quantitative PCR, respectively. No-tillage with residue retention significantly increased fungal richness but had little effect on bacterial diversity. Permutational multivariate analysis of variance showed that both tillage and sampling time had significant influences on fungal community structure, whereas the bacterial community structure was only affected by the sampling time, indicating that fungi were more sensitive than bacteria to tillage practices. Relative abundances of some fungal and bacterial genera changed significantly under no-tillage and residue treatments, with the greatest change found in the 33% mulching treatment. In addition, the quantitative PCR results showed that no-tillage with residue retention significantly increased F. graminearum and F. moniliforme abundances, suggesting that the risk of maize foot rot increased in the corn field. Spearman correlation analysis revealed that the abundances of these two pathogenic fungi were associated with soil properties and some microbial genera. Furthermore, no-tillage with 33% and 100% mulching had the greatest effect on F. graminearum and F. moniliforme abundances. These findings can provide some guidance for tillage and residue management practices of maize cropping in northeast China.