Agriculture Reference
In-Depth Information
Introduction
Bio-fertilizers are microbial inoculants of bacteria, algae, fungi that augment the
availability of nutrients to the plants. Use of bio-fertilizers, in contrast to chemical
fertilizers, accounts economical and ecological benefits to farmers (Brahmaprakash
and Sahu
2012
). Different types of microorganisms show the potential of converting
essential soil nutrients which are in unavailable form to available form with the help
of biological activity biological process such as nitrogen fixation and solubilization
of rock phosphate (Rokhzadi et al.
2008
). Bio-fertilizers improve plant growth, pro-
tect plants from amelioration of toxic effect in soils, root pest and disease control,
improved water usage and soil fertility (Halim
2009
; El-yazeid et al.
2007
; Badawi
et al.
2011
; Mader et al.
2011
; Mohammadi and Sohrabi
2012
).
In addition they get engaged in symbiotic as well as associative microbial activi-
ties with higher plants Tiwari et al. 2003. These being an economical and safer source
of plant nutrition for increasing the agricultural production, improve soil fertility and
are called mini fertilizer factories (Vyas et al.
2008
). The microorganisms form root
nodules in leguminous plants by colonizing roots of legumes. Nitrogen fixation, phos-
phorus solublization and phytohormone production abilities have been observed and
result in enhancement of agricultural productivity, e.g.
Rhizobium
for legumes (grain,
fodder) (Ali et al.
2010
) plant growth promoting rhizobacteria (PGPR) for cereals
(wheat, rice, grasses etc.),
Azolla
for rice ecosystem, and actinomycetes (
Frankia
spp.) (Zhang et al.
2012
), for forest trees (Danso et al.
1992
). These microorganisms
also have the ability to convert atmospheric nitrogen to plant usable form and can pro-
vide up to 200 kg N/ha/crop. Besides nitrogen, phosphorus is an essential element for
crop production. Another group of bacteria which play important role in stimulating
growth of plants are plant growth-promoting rhizobacteria (PGPR), they in addition
to stimulating growth of plants also control plant pathogens, and pest infestation i.e
they act as bio-fertilizers as well as biopesticides and ought to have meticulous con-
sideration for agricultural purposes (Lugtenberg and Kamilova
2009
). PGPR colo-
nizes the rhizosphere, i.e, around the root, and even in the intercellular spaces of root.
Advantages of Bio-fertilizers over Chemical Fertilizers
Uses of microbial products have various advantages over traditional chemicals for
agricultural purposes (Mahdi et al.
2010
). These products have been commended
safer than many of the chemicals that are used, they can fix atmospheric nitrogen
in nodules of leguminous plants and soil and make it available to the plants and in-
crease the fertility of soil (Shankar et al.
2012
). They solublize the insoluble forms
of phosphorous and again make is available to the plants (Hashemabadi et al.
2012
),
they also produce hormones which promote the growth of rhizosphere in addition to
these properties they also help in mineralization of soil by decomposing the organic
matter (Mahdi et al.
2010
).
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