MSc.

Ginger is one of the major spice crops of Kerala. Several constraints
hinder its production and the major one is its succeptibility to various diseases.
This has led to the use of high doses of chemical pesticides. Ginger is also a
highly nutrient exhausting crop, which demands use of high doses of fertilizers.
Although, chemical fertilizers and pesticides are highly effective, their continuous
use has led to many environmental problems. Alternative approaches are therefore
needed to minimize the use of chemical fertilizers and agrochemicals, since ginger
is directly consumed. Emphasis should be given for the organic cultivation of
ginger. The role of bioinoculants assumes special significance in this context. The
magnitude of plant growth promoting activities is reported to be better in the case
of consortia or mixed cultures than single strain. Therefore, bioinoculants
formulation consisting of biofertilizer and biocontrol agent would be a novel
technology which will provide nutrients as well as manage diseases. The literature
on the use of consortia of biofertilizers and biocontrol agents are scanty. Hence, a
study was undertaken on “Evaluation of bioinoculant consortia for organic
cultivation of ginger’’ with an objective to evaluate and find a suitable consortia
of bioinoculants for ginger cultivation.
Azospirillum lipoferum, phosphate solubilizing bacteria (PSB), potash
solubilizing bacteria (KSB), Pseudomonas fluorescens and Trichoderma viride
cultures of KAU were used for the study. When tested for their compatibility with
each other, it was found that Azospirillum lipoferum, PSB, KSB, Pseudomonas
fluorescens were mutually compatible with each other. However, Pseudomonas
fluorescens and Trichoderma viride were incompatible.
Based on the compatibility test, consortia consisting of biofertilizers alone
and biofertilizer + biocontrol agents were selected for the field evaluation. The
consortia KAU-AZO +KAU- PSB + KAU-KSB, KAU-AZO + KAU-PSB +
KAU-KSB + KAU-PF and KAU-AZO + KAU-PSB + KAU-KSB + KAU-TV
were selected. These consortia were compared with individual bioinoculants,
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PGPR Mix I, PGPR Mix II, Organic adhoc package (KAU, 2009) and POP
recommendation (KAU, 2011).
Based on the overall biometric and yield parameters, T11 (Organic adhoc
package, KAU, 2009) was found to be best among all the treatments evaluated.
Among the consortia, days taken for germination was minimum (17.33) in
the case of T6 (KAU-AZO+KAU-PSB+ KAU-KSB) while both T7 (KAUAZO+
KAU-PSB+ KAU-KSB +KAU-PF) and T8 (KAU-AZO+KAU-PSB+ KAUKSB
+KAU-TV) recorded the highest per cent (91.67) germination. Plant height,
number of tillers, and yield were maximum in T8 (KAU-AZO+KAU-PSB+ KAUKSB
+KAU-TV).
With regard to disease and pest incidence, T8 (KAU-AZO + KAU-PSB +
KAU-KSB + KAU-TV) recorded minimum per cent rhizome rot (5.23%)
incidence. However, T7 (KAU-AZO+KAU-PSB+ KAU-KSB +KAU-PF)
recorded the minimum per cent incidence (5.21) of Rhizoctonia leaf blight and
shoot-borer (4.17 %). The T6 treatment (KAU-AZO+KAU-PSB+ KAU-KSB) was
the least succeptible (6.25 %) to rhizome maggots.
At the time of harvest, T7 (KAU-AZO+KAU-PSB+KAU-KSB +KAU-PF)
and T8 (KAU-AZO+KAU-PSB+ KAU-KSB +KAU-TV) recorded the lowest pH
(5.30) and T8 (KAU-AZO + KAU-PSB+ KAU-KSB+ KAU-TV) registered
highest available nitrogen (188.68 kg/ha) among the consortia. However, highest
organic carbon (1.55 %) and available phosphorus (37.44 kg/ha) was recorded in
T7 (KAU-AZO+KAU-PSB+KAU-KSB+ KAU-PF). All the consortial treatments
were on par with each other with respect to available potassium content in soil.
Population of inoculated individual and consortial isolates in soil indicated a
decreasing trend till the time of harvest. The population decreased from 108 cfu/ml
to 104 cfu/ml in the case of bacteria and 106 to 10 3 cfu/ml in the case of fungus.
The Benefit:Cost ratio was maximum (1.65) in the case of T8 (KAU-AZO +
KAU-PSB + KAU-KSB + KAU-TV).
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The present studies clearly indicated that consortia inoculated plants
performed better than the individual isolates. The consortia of bioinoculants
treated plants were on par, but T8 (KAU-AZO + KAU-PSB + KAU-KSB + KAUTV)
was the most promising treatment among the consortia. Therefore, it can be
concluded that bioinoculant consortia consisting of bioagents for nutrient fixation
/solubilization (N, P, K) and fungicidal effect would be a novel technology in
present-day agriculture.