N Fertilization Dependent Bacterial and Archaeal …
73
is incorporated into the field which undergoes multi-stage anoxic degradation into
plant available nutrients. In such condition, fertilization with organic amendments
rapidly declines the oligotrophs while shooting up the OTU of copiotrophic straw
decomposers thereby determining a well-organized bacterial decomposers compared
to non-fertilized or synthetic fertilizer amended soil [110]. In yet other outlook, it is
claimed that rather than different fertilization, upland-rotation creates a considerable
shift in paddy microbiome promoting soil sustainability [40]. Additionally, there
is an interesting documentation that soil variables such as pH imparts significant
effect on microbial diversity rather than geographic distance [45]. A continental-scale
analyses also revealed a positive correlation between chemo-diversity of dissolved
soil organic matter and microbial taxonomic profile wherein both play a significant
role in soil biogeochemical cycle [59]. However, the crop itself capable of recruiting
the associated microbiome, shapes the root-associated bacteria and archaea based on
its stage of growth. It is reported that paddy root is colonized by diversified microbial
communities in the early stage. While, few taxa outcompetes all other communities
and colonize paddy rhizosphere in the later stages based on the selection by the host
rather than above listed factors [28]. In a nutshell, paddy microbiota is predominantly
decided by soil physicochemical variables, fertilization, geographic distance, age of
the plant and upland-lowland rotation systems.
4 Organic Versus Inorganic N Supplements
Application of urea and ammonium sulfate contributes to the N source for paddy fields
in most of the countries as paddy prefers NH 4
+ more than NO 3
− [29]. The applied
organic manures also get converted into ammonia through mineralization mediated
by soil associated microbes. Organic amendments including biochar of bamboo and
paddy straw are also recommended to retain N in paddy field by preventing its
leaching under water logged condition [27]. While listing the organic sources of N
in paddy field, the contribution of the aquatic fern, Azolla and its associative bacteria
Anabaena azollae becomes inevitable. In general, rice ecosystem emits CH 4 and
N 2 O while serving as a huge depository for CO 2 . Apart from their primary role in
fixation of atmospheric N, Azolla cover also decreases the emission of methane from
paddy field possibly by increasing the concentration of dissolved oxygen [54]. Paddyassociated microbes play an inevitable role in C and N biogeochemical cycling so
as to maintain a positive carbon and nitrogen budget in the soil. Rice ecosystem is
also amended with diversified organic supplements which exerts varying effects on
paddy microbiota in correlation with global warming. A higher load of heterotrophic
bacterial, fungal, actinobacterial and denitrifying bacterial populations were evident
in green manure-amended soil followed by soils that received integrated nutrient with
organic and inorganic fertilizer [73]. For instance, optimum application of inorganic
N fertilizer significantly declined CH 4 emission, while amendment of wheat straw
raised up its emission considerably contributing to global warming [64]. Foresaid
results were re-validated by documenting increase in the population of methanogenic
73
is incorporated into the field which undergoes multi-stage anoxic degradation into
plant available nutrients. In such condition, fertilization with organic amendments
rapidly declines the oligotrophs while shooting up the OTU of copiotrophic straw
decomposers thereby determining a well-organized bacterial decomposers compared
to non-fertilized or synthetic fertilizer amended soil [110]. In yet other outlook, it is
claimed that rather than different fertilization, upland-rotation creates a considerable
shift in paddy microbiome promoting soil sustainability [40]. Additionally, there
is an interesting documentation that soil variables such as pH imparts significant
effect on microbial diversity rather than geographic distance [45]. A continental-scale
analyses also revealed a positive correlation between chemo-diversity of dissolved
soil organic matter and microbial taxonomic profile wherein both play a significant
role in soil biogeochemical cycle [59]. However, the crop itself capable of recruiting
the associated microbiome, shapes the root-associated bacteria and archaea based on
its stage of growth. It is reported that paddy root is colonized by diversified microbial
communities in the early stage. While, few taxa outcompetes all other communities
and colonize paddy rhizosphere in the later stages based on the selection by the host
rather than above listed factors [28]. In a nutshell, paddy microbiota is predominantly
decided by soil physicochemical variables, fertilization, geographic distance, age of
the plant and upland-lowland rotation systems.
4 Organic Versus Inorganic N Supplements
Application of urea and ammonium sulfate contributes to the N source for paddy fields
in most of the countries as paddy prefers NH 4
+ more than NO 3
− [29]. The applied
organic manures also get converted into ammonia through mineralization mediated
by soil associated microbes. Organic amendments including biochar of bamboo and
paddy straw are also recommended to retain N in paddy field by preventing its
leaching under water logged condition [27]. While listing the organic sources of N
in paddy field, the contribution of the aquatic fern, Azolla and its associative bacteria
Anabaena azollae becomes inevitable. In general, rice ecosystem emits CH 4 and
N 2 O while serving as a huge depository for CO 2 . Apart from their primary role in
fixation of atmospheric N, Azolla cover also decreases the emission of methane from
paddy field possibly by increasing the concentration of dissolved oxygen [54]. Paddyassociated microbes play an inevitable role in C and N biogeochemical cycling so
as to maintain a positive carbon and nitrogen budget in the soil. Rice ecosystem is
also amended with diversified organic supplements which exerts varying effects on
paddy microbiota in correlation with global warming. A higher load of heterotrophic
bacterial, fungal, actinobacterial and denitrifying bacterial populations were evident
in green manure-amended soil followed by soils that received integrated nutrient with
organic and inorganic fertilizer [73]. For instance, optimum application of inorganic
N fertilizer significantly declined CH 4 emission, while amendment of wheat straw
raised up its emission considerably contributing to global warming [64]. Foresaid
results were re-validated by documenting increase in the population of methanogenic