Short-term effects of tillage practices and wheat straw returned to rice fields on top soil microbial community structure and microbial diversity in the middle part of China.

Soil microbial community which responses soil quality has been regarded as a sensitive indicator of soil ecosystems. A field experiment was conducted to investigate the effects of tillage practices and residue returning on top soi(l0～5 cm)microbial community structures and microbial diversity using phospholipid fatty acid(PLFA)at Junchuan town in Hubei Province of China. Treatments were established following a split-plot design of a randomized complete block with tillage practices[plough tillage(PT)and no-tillage(NT)] as the main plot and wheat straw returning level [6000 kg·hm-2 (SR3 ), 4000 kg·hm-2 (SR2 ), 2000 kg·hm-2 (SR1 )and 0 kg·hm-2 (SR0 )] as the subplot treatment. The results showed that the PLFAs of iC15:0, C16:0, 10Me17:0, Cyc19:0 were dominant in microbial community. They accounted for 9.6%～11.6%, 16.1%～19.0%, 8.7%～13.0% and 7.6%～9.8% of total PLFAs contents,respectively. The PLFAs contents of different treatments ranged from 25.35 nmol·g-1 to 43.06 nmol·g-1 . Tilling soil significantly enhanced the abundance of PLFAs indicator of fungi, Gram-negative bacteria, fungi/bacterial ratio, MUFA/STFA ratio and Shannon-Winner index, while G + /G -bacteria ratio decreased significantly under PT as compared with NT. Residue straw returning had a significant positive effect on bacteria, fungi, Gram-negative bacteria, Gram-positive bacteria, fungi/bacteria, Shannon-Winner, Simpson index and Margalf index. Therefore, our results suggest that wheat straw residue returned to paddy fields enhanced microbial community biomass and increased microbial diversity, while tillage practices signifi- cantly changed microbial community structure on paddy topsoil.