Effect of Fertilizer Levels ... India

and accelerated the breakdown of organic substances

population as compared to fungi in wheat rhizosphere

in the added manure, which is known to stimulate the

after harvest of the wheat in both the years of the

dehydrogenase activity (Pedrazzini and Mckee, 1984). The

experimentation. The results of experiment revealed that

significant increased of enzyme activity were also found

increasing fertilizer levels from 0 to 100% NPK, farmyard

by the use of bioinoculants (PGPR+VAM) as compared

manure @ 10 t ha -1 and co-inoculation with PGPR+VAM

to no inoculation control (Table 4). Increased the enzyme

significantly increased the bacterial and fungal population

activity of soil significantly over no inoculation, may

in the rhizosphere soil. Application of increasing levels

possibly be due to the improvement in the porosity and

of fertilizer increased the bacteria and fungi population

more availability of nutrients (especially P) to the plant

in rhizosphere soil significantly upto 75% NPK levels

(Shinde and Bangar, 2003).

and further increase to 100% NPK although resulted in

It is evident from data presented in Table 4, that the

slightly increase in population but was at par to 75%

contents of soil microbial biomass carbon (SMBC) varied

NPK levels. The increase in microbial population might

significantly under different treatment. The contents of

be due to increasing levels of N, P and K which increases

biomass carbon have decreased from its initial status

the biomass, root exudates and ultimately provides

(171 mg kg -1 soil) in control. The contents of SMBC

carbon and energy to the soil microbes resulting into

were the highest under application of 100% NPK (194.17

multiplication of microbial population (Geethakumari

and 195.83 mg kg -1 soil) during both the years. Microbial

and Shivashankar, 1991). The results are harmony with

biomass carbon increased with increase in doses of

the finding of Chand et al., ( 2010).

inorganic fertilizers may be due firstly to increase in

Similarly, application of FYM @ 10 t ha -1 enhanced

microbial population (Hasebe et al., 1985) and secondly

significantly higher values of soil bacteria and fungi

to the formation of root exudates, mucigel soughed off

population over no FYM application at the harvest of the

cells and underground roots of previous cut crops, which

wheat crop during both the years (Table 4). The increased

also play an important role in increasing biomass carbon

microbial population might be due to application of

(Goyal et al., 1992). The SMBC increased with fertilizer

organic manures in turn provides adequate biomass as a

level were also reported by Gogoi et al., (2010).

feed for the microbes and helps in increasing microbial

Application of FYM @ 10 t ha -1 significantly increased

population in soil (Singh et al., 2012).

the SMBC in soil during both the years. The SMBC at

The bioinoculants PGPR, VAM and PGPR+VAM

10 t FYM ha -1 being 184.52 and 186.79 mg kg -1 soil

either singly or in combination significantly increased

during 2009-10 and 2010-11, respectively. The extent

the population of microbes viz., bacteria and fungi

increase over no FYM (176.89 and 177.42 mg kg -1 soil)

in rhizosphere soil after harvest of wheat over no

was 4.31 and 5.28% during both the years. The higher

inoculation during both the years. The bioinoculants

microbial biomass in FYM might be due to higher

trigger the microbial population might be possibly due to

below ground plant residues as well as added FYM

the improvement in the porosity and more availability of

(Grego et al., 1998). Moreover the use of bioinoculants

nutrients (especially P) to the plant by the bioinoculants

in an integrated manner enhanced the microbial biomass

(Shinde and Bangar, 2003). Sushila and Giri (2000) also

carbon during both the years. The increase might be due

reported increase in microbial population in rhizosphere of

to integrated use of fertilizer, FYM and bioinoculants

wheat with Azospirillum and Azotobacter inoculations.

add more organic matter, which provide carbon and

energy to the soil microbes resulting into multiplication

Interaction effect of fertilizers and farm yard

of microbial population and increase in soil microbial

manures

biomass carbon during both the years. The results of the

present investigation are in accordance with the finding

Data presented in Table 3 show that there was significant

of Datt et al., (2013).

interactive effect of fertilizer levels and FYM application

on available P content of soil after harvest of wheat

Microbial population (Table 4) showed higher bacterial

during both the years. The available P content of soil

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