Agriculture Reference
In-Depth Information
Table 1.3
(continued)
Carrier material
Inoculant bacterium Characteristics
Wastewater sludge
Sinorhizobium
meliloti
Seed inoculants; result showed the
suitability of using sludge as a car-
rier because it had the same or a
higher potential than peat to sup-
port survival of
S. meliloti
Wheat bran, sugar cane bagasse
Rhizobium
/
Bradyrhizobium
and PS fungus,
A. niger
Soil inoculants; the number of micro-
organisms was the highest with
peat, followed by bran and sugar-
cane bagasse
Nutrient-supplemented pumice
Rhizobium
Seed inoculants; good storage and
handling properties and could be
mixed directly with the seeds dur-
ing the sowing process
use of any ideal carrier material is important in the production of good quality
microbial inoculants including microphos. Among various materials, peat soil,
lignite, vermiculite, charcoal, press mud, wastewater sludge, cow dung cake pow-
der, sawdust, farmyard manure (FYM) and soil mixture have been used by many
workers as carrier materials for producing the microbial inoculants (Ben Rebah
et al.
2002
; Trivedi et al.
2005
; Maheshwari
2008
; Khan et al.
2010
,
2013
). Of these
materials, the neutralized peat soil/lignite has been found as the better carrier
material for inoculant production. However, an ideal carrier should have these
properties: (i) it should be inexpensive, mixable, packageable and locally available
in powder or granular form in adequate quantities; (ii) the carrier must permit gas
exchange, particularly oxygen, and have high organic matter content (Bashan
1998
)
and water holding and retention capacity and it should be more than 50 %; (iii) it
should be easy to process (mixing, curing and packaging operations) and free of
lump-forming materials; (iv) it should be easy to sterilize by autoclaving or gamma-
irradiation; (v) it should have good adhesion to seeds (Hegde and Brahmaprakash
1992
) and good pH buffering capacity (Keyser et al.
1993
); (vi) it should be
non-toxic to inoculant bacterial strain and plant and easily biodegradable and
non-polluting; (vii) it should nearly be sterile and uniform; (viii) it should support
growth and survival of bacteria; and (ix) rapid release of bacteria in soil. For
preparation of seed inoculant, the carrier material is milled to fine powder with
particle size of 10-40
m. The selected carriers are then sterilized before mixing
with inoculum so that high number of inoculant bacteria can be maintained on
carrier for long storage period. Furthermore, carrier is sterilized to prevent unde-
sirable spreading of pathogenic bacteria to agricultural field. Different methods
have been adopted to sterilize the carrier materials in order to find the most suitable
one without any effect on their quality. In this context, gamma-irradiation has been
found as the most suitable way of sterilization since gamma-irradiation does not
alter the physical and chemical characteristics of the carrier materials. However,
there are other ways by which carrier materials can also be sterilized. Of these,
μ
