302
C. Pandey et al.
and also to increase the plant potential to produce more with the recommended dose
of fertilizers. This is quite possible by increasing the “Nutrient use efficiency” (NUE)
of the plants. It is the key component to enhance crop productivity. Generally, the
NUE is crop or variety-specific but, there are reports, which suggest that PGPRs can
effectively increase the NUE in different plants, result in higher crop productivity
and nutrient quality. Recent research on plant–microbe interaction has revealed that
PGPRs affect the ability of host plants to efficiently utilize the absorbed nutrients and
increase yield and nutritive quality of the produce (Pandey et al. 2018a, b; Rahman
et al. 2018).
13.2.3 PGPRs in NUE Enhancement
High crop yield is the result of adequate availability of nutrients in the soil and their
optimum uptake and accumulation in the plant systems. This, in turn, may enhance
the NUE of the plant. It has been reported that PGPR provides the optimum level of
nutrients to the plants and thereby increasing plant growth and yield (Pandey et al.
2018b; Rahman et al. 2018). Usually, nutrients are present in the soil but, generally,
they remain in plant unavailable form and PGPRs can convert them into the available
form (Adesemoye and Kloepper 2009).
PGPR group of bacteria are soluble in nature. Some of the bacterial genera increase
soil N, P, and K availability by solubilization and fixation reaction. PGPRs possess
different mechanisms for higher nitrogen availability which include ammonification,
nitrification, denitrification, mineralization, etc. (Ogunseitan 2005). A diverse range
of PGPRs are known to enhance nitrogen use efficiency, for instance, Acetobacter,
Azoarcus, Arthrobacter, Azotobacter, Azospirillum, Bacillus, Burkholderia, Enterobacter, Pseudomonas, Nitrobacter, Nitrosomonas, Rhizobium, etc. (Table 13.4).
Nitrogen use efficiency is the plants’ ability to utilize available nitrogen in the
field to enhance plant growth and productivity. To achieve the best NUE scientific researches were based on 4R principle, i.e., right source, right rate, right time,
and right placement. NUE depends on the transport, storage, recycling, remobilization, and plant growth stage along with the nutrient uptake. The synchronization
of nitrogen availability with nitrogen demand can increase nitrogen use efficiency
significantly.
Spolaor and coworkers (2016) suggested consortium of A. brasilense Ab-V5 +
V6 and consortium of A. brasilense Ab-V5 and Rhizobium sp 53GRM1 to be effective to enhance the NUE of popcorn and enhanced the grain yield. Zeffa et al. (2019)
applied A. brasilense Ab-V5 to improve maize growth and concluded that it increased
NUE in N limiting conditions along with the improved root architecture, N assimilation, uptake, and increased biomass. Authors concluded that the morphological and
structural changes in the plant occured because of the production of phytohormones
by A. brasilense Ab-V5. Ahmad et al. (2017) reported that the PGPR impregnation
with the DAP and urea enhanced nitrogen and phosphorus use efficiency of wheat
and thereby increased photosynthetic rate, growth, and yield.
C. Pandey et al.
and also to increase the plant potential to produce more with the recommended dose
of fertilizers. This is quite possible by increasing the “Nutrient use efficiency” (NUE)
of the plants. It is the key component to enhance crop productivity. Generally, the
NUE is crop or variety-specific but, there are reports, which suggest that PGPRs can
effectively increase the NUE in different plants, result in higher crop productivity
and nutrient quality. Recent research on plant–microbe interaction has revealed that
PGPRs affect the ability of host plants to efficiently utilize the absorbed nutrients and
increase yield and nutritive quality of the produce (Pandey et al. 2018a, b; Rahman
et al. 2018).
13.2.3 PGPRs in NUE Enhancement
High crop yield is the result of adequate availability of nutrients in the soil and their
optimum uptake and accumulation in the plant systems. This, in turn, may enhance
the NUE of the plant. It has been reported that PGPR provides the optimum level of
nutrients to the plants and thereby increasing plant growth and yield (Pandey et al.
2018b; Rahman et al. 2018). Usually, nutrients are present in the soil but, generally,
they remain in plant unavailable form and PGPRs can convert them into the available
form (Adesemoye and Kloepper 2009).
PGPR group of bacteria are soluble in nature. Some of the bacterial genera increase
soil N, P, and K availability by solubilization and fixation reaction. PGPRs possess
different mechanisms for higher nitrogen availability which include ammonification,
nitrification, denitrification, mineralization, etc. (Ogunseitan 2005). A diverse range
of PGPRs are known to enhance nitrogen use efficiency, for instance, Acetobacter,
Azoarcus, Arthrobacter, Azotobacter, Azospirillum, Bacillus, Burkholderia, Enterobacter, Pseudomonas, Nitrobacter, Nitrosomonas, Rhizobium, etc. (Table 13.4).
Nitrogen use efficiency is the plants’ ability to utilize available nitrogen in the
field to enhance plant growth and productivity. To achieve the best NUE scientific researches were based on 4R principle, i.e., right source, right rate, right time,
and right placement. NUE depends on the transport, storage, recycling, remobilization, and plant growth stage along with the nutrient uptake. The synchronization
of nitrogen availability with nitrogen demand can increase nitrogen use efficiency
significantly.
Spolaor and coworkers (2016) suggested consortium of A. brasilense Ab-V5 +
V6 and consortium of A. brasilense Ab-V5 and Rhizobium sp 53GRM1 to be effective to enhance the NUE of popcorn and enhanced the grain yield. Zeffa et al. (2019)
applied A. brasilense Ab-V5 to improve maize growth and concluded that it increased
NUE in N limiting conditions along with the improved root architecture, N assimilation, uptake, and increased biomass. Authors concluded that the morphological and
structural changes in the plant occured because of the production of phytohormones
by A. brasilense Ab-V5. Ahmad et al. (2017) reported that the PGPR impregnation
with the DAP and urea enhanced nitrogen and phosphorus use efficiency of wheat
and thereby increased photosynthetic rate, growth, and yield.