5. Conclusions
Long-term mineral and organic fertilization were demonstrated to have a
positive effect on microbial biomass enhancement. Our data clearly
showed that the soil microbial biomass and PLFAs decreased with soil
depth owing to decreasing available nutrients along soil profiles. The
microbial sensitivity of nutrients declined with soil depth in the
following order: fungi > G− bacteria > G+
bacteria > actinomycetes; this order cannot be changed by
fertilization type. Moreover, mineral fertilizers induced G+ bacteria
more than G− bacteria and actinomycetes, which suggested a close link
between G+ bacteria and mineral fertilizers. With equal fertilizer
input, straw addition especially promoted fungi at 10−20cm soil depth,
while chicken manure further stimulated G+ bacteria. In broader
perspective, understanding the mechanisms of microbial group shift due
to fertilization in paddy systems may help improving soil quality
through better fertilization management. Further studies should include
isotope analyses (13C, 14C,15N) and microbial molecular analyses (16S rRNA
sequencing, PLFA, SIP, etc) to fully reveal the fertilizer nutrient
turnover in situ in paddy soil systems.
Conflict of interest statement: The authors declare no conflict
of interest.
Data Availability Statement: The data that support the findings
of this study are available from the corresponding author upon
reasonable request.