Abstract:
Shifting agricultural soil ecosystem represents stress of varying
degrees depending upon the length of the fallow cycle. In this study, we
try to assess the synergistic effect of microbial diversity on different
rhizospheric niches (loosely adhered and strongly adhered rhizosphere
soil, bulk soil, and the crop root interior) of different fallow cycles
(5, 8, and 20 years) using culture-dependent and independent approaches
along with their metabolic profiling. Culture dependent study shows
higher bacterial diversity in strongly adhered rhizosphere soil followed
by loosely adhered rhizosphere soil (F = 156, p < 0.001)
irrespective of crop type and fallow cycle length. The high-throughput
16S rRNA gene sequencing shows 5% higher bacterial diversity in 5 years
than in 8 and 20 years fallow soil (p < 0.05). The community
composition was significantly affected by the length of fallow periods
in all rhizosphere niches, driven primarily by an increased relative
abundance of Proteobacteria and Bacteroidetes in long than
short fallow cycles. We have observed a selective promotion of
rhizobacterial communities in different niches of low nutrient soil in
the short fallow period that complies with the crop field’s bacterial
metabolic pathways. Our study answers an inconclusive question on
bacterial diversity dynamics in shifting field crop rhizosphere and
soil, highlighting the predominant role of bacterial community in the
crop grown in a stressed soil system. This study may provide a
scientific roadmap in developing microbial inoculum for better crop
performance in nutrient-poor soil.
Keywords: Shifting agriculture, fallow cycle, rhizosphere niches,
bacterial community.