1. Journal of Phytology 2010, 2(10): 42-54 ISSN: 2075-6240
An Open Access Journal Available Online: www.journal-phytology.com
REVIEW ARTICLE
BIO-FERTILIZERS IN ORGANIC AGRICULTURE
S. Sheraz Mahdi1*, G. I. Hassan2, S. A. Samoon3, H. A. Rather4, Showkat A. Dar5 and B.
Zehra6
1Divisionof Agronomy, Sher-e Kashmir University of Agricultural Sciences and Technology of Kashmir,
Shalimar, Srinagar, J & K-India-1911211
2Division of Pomology, Sher-e Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar,
Srinagar, J & K-India-191121
3Division of Floriculture, Sher-e Kashmir University of Agricultural Sciences and Technology of Kashmir,
Shalimar, Srinagar, J & K-India-191121
4Faculty of Forestry, Sher-e Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar,
Srinagar, J & K-India-191121
5Division of Entomology, Sher-e Kashmir University of Agricultural Sciences and Technology of Kashmir,
Shalimar, Srinagar, J & K-India-191121
6Faculty of Horticulture, Sher-e Kashmir University of Agricultural Sciences and Technology of Kashmir,
Shalimar, Srinagar, J & K-India-191121
SUMMARY
Experiencing the adverse effects of synthetic input dependent agriculture the concept of
organic agriculture is gaining momentum. Almost 31 million hectares of land are
currently managed organically by more than 6, 00, 000 farmers worldwide, constitutes
0.7 per cent of agriculture land. India had brought more than 2.5 m ha land under
certification of organics. In these systems production is based in synergism with nature,
which makes systems of unending life i.e. sustainable. Deteriorative effects of synthetic
chemical inputs are obvious, but, at the same time we need to revive soil health and
living which support to sustainable production system. Soil environment needs to be
made congenial for living of useful microbial population, responsible for continuous
availability of nutrients from natural sources.
Bio-fertilizers being essential components of organic farming play vital role in
maintaining long term soil fertility and sustainability by fixing atmospheric dinitrogen
(N=N), mobilizing fixed macro and micro nutrients or convert insoluble P in the soil into
forms available to plants, there by increases their efficiency and availability. Currently
there is a gap of ten million tonnes of plant nutrients between removal of crops and
supply through chemical fertilizers. In context of both the cost and environmental impact
of chemical fertilizers, excessive reliance on the chemical fertilizers is not viable strategy
in long run because of the cost, both in domestic resources and foreign exchange,
involved in setting up of fertilizer plants and sustaining the production. In this context,
organic manures (bio-fertilizers) would be the viable option for farmers to increase
productivity per unit area.
The mycorrhizal associations (VAM) in alleviating Al toxicity, increasing N, P and
micronutrient uptake, maintaining soil structure by the production specific protein called
“Glomulin” has been repeatedly demonstrated. Liquid bio-fertilizer technology now,
shares more advantage over conventional carrier based bio-fertilizers and can be
considered as a breakthrough in field of Bio-fertilizer technology and should find greater
acceptance by farmers, extension workers and commercial bio-fertilizer manufactures. In
this review, the established facts observed and the work carried out by many researchers
on bio-fertilizers is discussed.
Key words: Bio-fertilizers, Crop growth, Sustainability, VA-mycorrhizae
S. Sheraz Mahdi et al. Bio-fertilizers in Organic Agriculture. J Phytol 2/10 (2010) 42-54
*Corresponding Author, Email: sheerazsyed@rediffmail.com

2. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
1. Introduction considerable opportunity for organic farming
Organic farming has emerged as an due to least utilization of chemical inputs. It
important priority area globally in view of is estimated that 18 million hectare of such
the growing demand for safe and healthy land is available in the NE that can be
food and long term sustainability and exploited for organic production. With the
concerns on environmental pollution sizable acreage under naturally
associated with indiscriminate use of agro- organic/default organic cultivation, India
chemicals. Though the use of chemical inputs has tremendous potential to grow crops
in agriculture is inevitable to meet the organically and emerge as a major supplier
growing demand for food in world, there are of organic products in world’s organic
opportunities in selected crops and niche market (Venkatashwarlu. 2008a) The report
areas where organic production can be of Task Force on Organic Farming appointed
encouraged to tape the domestic export by the Government of India also observed
market. that in vast areas of the country, where
Bio-fertilizers are being essential limited amount of chemicals are used and
component of organic farming are the have low productivity could be exploited as
preparations containing live or latent cells of potential areas to develop into organic
efficient strains of nitrogen fixing, phosphate agriculture. Arresting the decline of soil
solubilizing or cellulolytic micro-organisms organic matter is the most potent weapon in
used for application to seed, soil or fighting against unabated soil degradation
composting areas with the objective of and imperiled sustainability of agriculture in
increasing number of such micro-organisms tropical regions of India, particularly those
and accelerate those microbial processes under the influence of arid, semiarid and
which augment the availability of nutrients sub-humid climate. Application of organic
that can be easily assimilated by plants. Bio- manures particularly bio-fertilizers is the
fertilizers play a very significant role in only option to improve the soil organic
improving soil fertility by fixing atmospheric carbon for sustenance of soil quality and
nitrogen, both, in association with plant roots future agricultural productivity (Ramesh,
and without it, solubilise insoluble soil 2008).
phosphates and produces plant growth
substances in the soil. They are in fact being Why to explore bio-fertilizers:-
promoted to harvest the naturally available, Indiscriminate use of synthetic fertilizers
biological system of nutrient mobilization has led to the pollution and contamination of
(Venkatashwarlu, 2008a). The role and the soil, has polluted water basins, destroyed
importance of biofertilizers in sustainable micro-organisms and friendly insects,
crop production has been reviewed by making the crop more prone to diseases and
several authors (Biswas et al. 1985; Wani and reduced soil fertility.
Lee, 1995; Katyal et al. 1994). But the • Demand is much higher than the
progress in the field of BF production availability. It is estimated that by
technology remained always below 2020, to achieve the targeted
satisfaction in Asia because of various production of 321 million tonnes of
constraints. food grain, the requirement of
It may be noted, only 30 % of India’s total nutrient will be 28.8 million tonnes,
cultivable area is covered with fertilizers while their availability will be only
where irrigation facilities are available and 21.6 million tones being a deficit of
the remaining 70 % of the arable land, which about 7.2 million tones.
is mainly rain fed, very negligible amount of • Depleting feedstock/fossil fuels
fertilizers are being used. Farmers in these (energy crisis) and increasing cost of
areas often use organic manures as a source fertilizers. This is becoming
of nutrients that are readily available either unaffordable by small and marginal
in their own farm or in their locality. The farmers.
North- Eastern (NE) region of India provides

3. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
• Depleting soil fertility due to needed to restore the population of effective
widening gap between nutrient strains of the Rhizobium near the rhizosphere
removal and supplies. to hasten N-fixation. Each legume requires a
• Growing concern about specific species of Rhozobium to form
environmental hazards. effective nodules. Many legumes may be
• Increasing threat to sustainable modulated by diverse strains of Rhizobia, but
agriculture. growth is enhanced only when nodules are
Besides above facts, the long term use of produced by effective strains of Rhizobia. It is
bio-fertilizers is economical, eco-friendly, thus extremely important to match
more efficient, productive and accessible to microsymbionts prudently for maximum
marginal and small farmers over chemical nitrogen fixation. A strain of Rhizobia that
fertilizers (Venkataraman and nodulates and fixes a large amount of
Shanmugasundaram, 1992). nitrogen in association with one legume
species may also do the same in association
Estimated demand and supply of some with certain other legume species. This must
important bio-fertilizers in India be verified by testing. Leguminous plants
The annual requirement and production that demonstrate this tendency to respond
of different bio-fertilizers have clearly shown similarly to particular strains of Rhizobia are
tremendous gap in this area. Thus a strategy considered “effectiveness” group (Wani and
for judicious combination of chemical Lee 2002).
fertilizers and biofertilizers will be
economically viable and ecological useful. It Azospirillum: belongs to family
should be recommended that biofertilizers Spirilaceae, heterotrophic and associative in
are not a substitute, but a supplement to nature. In addition to their nitrogen fixing
chemical fertilizers for maximizing not only ability of about 20-40 kg/ha, they also
the yield but also agro system stability. produce growth regulating substances.
Although there are many species under this
genus like, A.amazonense, A.halopraeferens,
2. Potential characteristic features of A.brasilense, but, worldwide distribution and
some bio-fertilizers benefits of inoculation have been proved
Nitrogen fixers mainly with the A.lipoferum and A.brasilense.
Rhizobium: belongs to family Rhizobiaceae, The Azospirillum form associative symbiosis
symbiotic in nature, fix nitrogen 50-100 kg/ with many plants particularly with those
ha. with legumes only. It is useful for pulse having the C4-dicarboxyliac path way of
legumes like chickpea, red-gram, pea, lentil, photosynthesis (Hatch and Slack pathway),
black gram, etc., oil-seed legumes like because they grow and fix nitrogen on salts
soybean and groundnut and forage legumes of organic acids such as malic, aspartic acid
like berseem and lucerne. Successful (Arun, 2007a). Thus it is mainly
nodulation of leguminous crops by recommended for maize, sugarcane,
Rhizobium largely depends on the availability sorghum, pearl millet etc. The Azotobacter
of compatible strain for a particular legume. colonizing the roots not only remains on the
It colonizes the roots of specific legumes to root surface but also a sizable proportion of
form tumour like growths called root them penetrates into the root tissues and
nodules, which acts as factories of ammonia lives in harmony with the plants. They do
production. Rhizobium has ability to fix not, however, produce any visible nodules or
atmospheric nitrogen in symbiotic out growth on root tissue.
association with legumes and certain non-
legumes like Parasponia. Rhizobium Azotobacter: belongs to family
population in the soil depends on the Azotobacteriaceae, aerobic, free living, and
presence of legume crops in the field. In heterotrophic in nature. Azotobacters are
absence of legumes, the population present in neutral or alkaline soils and A.
decreases. Artificial seed inoculation is often chroococcum is the most commonly occurring

4. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
species in arable soils. A. vinelandii, A. BGA forms symbiotic association capable of
beijerinckii, A. insignis and A. macrocytogenes fixing nitrogen with fungi, liverworts, ferns
are other reported species. The number of and flowering plants, but the most common
Azotobacter rarely exceeds of 104 to 105 g-1 of symbiotic association has been found
soil due to lack of organic matter and between a free floating aquatic fern, the
presence of antagonistic microorganisms in Azolla and Anabaena azollae (BGA). Azolla
soil. The bacterium produces anti-fungal contains 4-5% N on dry basis and 0.2-0.4% on
antibiotics which inhibits the growth of wet basis and can be the potential source of
several pathogenic fungi in the root region organic manure and nitrogen in rice
thereby preventing seedling mortality to a production. The important factor in using
certain extent (Subba Rao, 2001a). The Azolla as biofertilizer for rice crop is its quick
isolated culture of Azotobacter fixes about 10 decomposition in the soil and efficient
mg nitrogen g-1 of carbon source under in availability of its nitrogen to rice plants
vitro conditions. Azotobacter also to known to (Kannaiyan, 1990). Besides N-fixation, these
synthesize biologically active growth biofertilizers or biomanures also contribute
promoting substances such as vitamins of B- significant amounts of P, K, S, Zn, Fe, Mb
group, indole acetic acid (IAA) and and other micronutrient. The fern forms a
gibberellins. Many strains of Azotobacter also green mat over water with a branched stem,
exhibited fungi static properties against plant deeply bilobed leaves and roots. The dorsal
pathogens such as Fusarium, Alternaria and fleshy lobe of the leaf contains the algal
Helminthosporium. The population of symbiont within the central cavity. Azolla
Azotobacter is generally low in the can be applied as green manure by
rhizosphere of the crop plants and in incorporating in the fields prior to rice
uncultivated soils. The occurrence of this planting. The most common species
organism has been reported from the occurring in India is A. pinnata and same can
rhizosphere of a number of crop plants such be propagated on commercial scale by
as rice, maize, sugarcane, bajra, vegetables vegetative means. It may yield on average
and plantation crops, (Arun, 2007a). about 1.5 kg per square meter in a week.
India has recently introduced some species of
Blue Green Algae (Cyanobacteria) and Azolla for their large biomass production,
Azolla: These belongs to eight different which are A.caroliniana, A. microphylla, A.
families, phototrophic in nature and produce filiculoides and A. mexicana.
Auxin, Indole acetic acid and Gibberllic acid,
fix 20-30 kg N/ha in submerged rice fields as Phosphate solubilizers
they are abundant in paddy, so also referred Several reports have examined the ability
as ‘paddy organisms’. N is the key input of different bacterial species to solubilize
required in large quantities for low land rice insoluble inorganic phosphate compounds,
production. Soil N and BNF by associated such as tricalcium phosphate, dicalcium
organisms are major sources of N for low phosphate, hydroxyapatite, and rock
land rice. The 50-60% N requirement is met phosphate. Among the bacterial genera with
through the combination of mineralization of this capacity are pseudomonas, Bacillus,
soil organic N and BNF by free living and Rhizobium, Burkholderia, Achromobacter,
rice plant associated bacteria (Roger and Agrobacterium, Microccocus, Aereobacter,
Ladha, 1992). To achieve food security Flavobacterium and Erwinia. There are
through sustainable agriculture, the considerable populations of phosphate-
requirement for fixed nitrogen must be solubilizing bacteria in soil and in plant
increasingly met by BNF rather than by rhizospheres. These include both aerobic
industrial nitrogen fixation. Most N fixing and anaerobic strains, with a prevalence of
BGA are filamentous, consisting of chain of aerobic strains in submerged soils. A
vegetative cells including specialized cells considerably higher concentration of
called heterocyst which function as micro phosphate solubilizing bacteria is commonly
nodule for synthesis and N fixing machinery. found in the rhizosphere in comparison with

5. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
non rhizosphere soil (Raghu and Macrae, genera of fungi that contain species, which
2000). The soil bacteria belonging to the are known to produce Arbuscular mycorrhizal
genera Pseudomonas and Bacillus and Fungi fungi (AMF) with plants. Two of these genera,
are more common. The major Glomus and Sclerocytis, produce
microbiological means by which insoluble-P chlamydospores only. Four genera form
compounds are mobilized is by the spores that are similar to azygospores:
production of organic acids, accompanied by Gigaspora, Scutellospora, Acaulospora and
acidification of the medium. The organic and Entrophospora. The oldest and most prevalent
inorganic acids convert tricalcium phosphate of these associations are the arbuscular
to di- and- monobasic phosphates with the mycorrhizal (AM) symbioses that first
net result of an enhanced availability of the evolved 400 million years ago, coinciding
element to the plant. The type of organic acid with the appearance of the first land plants.
produced and their amounts differ with Crop domestication, in comparison, is a
different organisms. Tri- and di-carboxylic relatively recent event, beginning 10, 000
acids are more effective as compared to years ago (Sawers et al. 2007).
mono basic and aromatic acids. Aliphatic
acids are also found to be more effective in P- Zinc solubilizers
solubilization compared to phenolic, citric The nitrogen fixers like Rhizobium,
and fumaric acids. The analysis of culture Azospirillum, Azotobacter, BGA and Phosphate
filtrates of PSMs has shown the presence of solubilizing bacteria like B. magaterium,
number of organic acids including citric, Pseudomonas striata, and phosphate
fumaric, lactic, 2-ketogluconic, gluconic, mobilizing Mycorrhiza have been widely
glyoxylic and ketobutyric acids. accepted as bio-fertilizers (Subba Roa, 2001a).
However these supply only major nutrients
Phosphate absorbers but a host of microorganism that can
Mycorrhiza (an ancient symbiosis in transform micronutrients are there in soil
organic agriculture) that can be used as bio-fertilizers to supply
The term Mycorrhiza denotes “fungus micronutrients like zinc, iron, copper etc.,
roots”. It is a symbiotic association between zinc being utmost important is found in the
host plants and certain group of fungi at the earth’s crust to the tune of 0.008 per cent but
root system, in which the fungal partner is more than 50 per cent of Indian soils exhibit
benefited by obtaining its carbon deficiency of zinc with content must below
requirements from the photosynthates of the the critical level of 1.5 ppm of available zinc
host and the host in turn is benefited by (Katyal and Rattan, 1993). The plant
obtaining the much needed nutrients constraints in absorbing zinc from the soil
especially phosphorus, calcium, copper, zinc are overcome by external application of
etc., which are otherwise inaccessible to it, soluble zinc sulphate (ZnSO4). But the fate of
with the help of the fine absorbing hyphae of applied zinc in the submerged soil conditions
the fungus. These fungi are associated with is pathetic and only 1-4% of total available
majority of agricultural crops, except with zinc is utilized by the crop and 75% of
those crops/plants belonging to families of applied zinc is transformed into different
Chenopodiaceae, Amaranthaceae, mineral fractions (Zn-fixation) which are not
Caryophyllaceae, Polygonaceae, Brassicaceae, available for plant absorption (crystalline
Commelinaceae, Juncaceae and Cyperaceae. They iron oxide bound and residual zinc). There
are ubiquitous in geographic distribution appears to be two main mechanisms of zinc-
occurring with plants growing in artic, fixation, one operates in acidic soils and is
temperate and tropical regions alike. VAM closely related with cat ion exchange and
occur over a broad ecological range from other operates in alkaline conditions where
aquatic to desert environments (Mosse et al. fixation takes by means of chemisorptions, (
1981). Of 150 species of fungi that have been chemisorptions of zinc on calcium carbonate
described in order Glomales of class formed a solid-solution of ZnCaCO3), and by
Zygomycetes, only small proportions are
presumed to be mycorrhizal. There are six

6. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
complexation by organic ligands (Alloway, effects on plant yields. The effect of
2008). Azotobacter chroococcum on vegetative growth
The zinc can be solubilized by and yields of maize has been studied by
microorganisms viz., B. subtilis, Thiobacillus numerous authors (Hussain et al., 1987;
thioxidans and Saccharomyces sp. These Martinez Toledo et al., 1988; Nieto and
microorganisms can be used as bio-fertilizers Frankenberger, 1991; Mishra et al., 1995;
for solubilization of fixed micronutrients like Pandey et al., 1998; Radwan, 1998), as well as
zinc (Raj, 2007). The results have shown that the effect of inoculation with this bacterium
a Bacillus sp. (Zn solubilizing bacteria) can be on wheat (Emam et al., 1986; Rai and Gaur,
used as bio-fertilizer for zinc or in soils 1988; Tippanavar and Reddy, 1993,
where native zinc is higher or in conjunction Elshanshoury, 1995; Pati et al., 1995; Fares,
with insoluble cheaper zinc compounds like 1997a).
zinc oxide (ZnO), zinc carbonate (ZnCO3) Alkaline phosphatase activity in the
and zinc sulphide (ZnS) instead of costly zinc peach roots was highest with Azotobacter
sulphate (Mahdi et al. 2010). chroococcum + P fertilizer (Godara et al., 1995).
Results of a greenhouse pot experiments
3. Potential role of bio-fertilizers in with onion showed that application of G.
agriculture fasciculatum + A. chrooccocum + 50% of the
Nitrogen-fixers (NF) and Phosphate recommended P rate resulted in the greatest
solubilizers (PSBs) root length, plant height, bulb girth, bulb
The incorporation of bio-fertilizers (N- fresh weight, root colonization and P uptake
fixers) plays major role in improving soil (Mandhare et al. 1998). Inoculation with
fertility, yield attributing characters and Azotobacter + Rhizobium + VAM gave the
thereby final yield has been reported by highest increase in straw and grain yield of
many workers (Subashini et al. 2007a; wheat plants with rock phosphate as a P-
Kachroo and Razdan, 2006; Son et al. 2007). fertilizer (Fares, 1997a). Elgala et al. (1995)
In addition, their application in soil improves concluded that with microbial inoculation
soil biota and minimizes the sole use of rock phosphate could be used as cheap
chemical fertilizers (Subashini et al. 2007a). source of P in alkaline soils and that
Under temperate conditions, inoculation combined inoculation could reduce the rate
of Rhizobium improved number of pods of fertilizer required to maintain high
plant-1, number of seed pod-1 and 1000-seed productivity.
weight (g) and thereby yield over the control. It is an established fact that the efficiency
The number of pods plant-1, number of seed of phosphatic fertilizers is very low (15-20%)
pod-1 and 1000-seed weight (g) recorded due to its fixation in acidic and alkaline soils
were 25.5, 17.1 and 4.7 per cent more over the and unfortunately both soil types are
control, respectively which was statistically predominating in India accounting more
significant Bhat et al. (2009). In rice under low than 34% acidity affected and more than
land conditions, the application of BGA+ seven million hectares of productive land
Azospirillum proved significantly beneficial in salinity/alkaline affected (Yawalkar et al.,
improving LAI and all yield attributing 2000). Therefore, the inoculations with PSB
aspects. Grain yield and harvest index also and other useful microbial inoculants in
exhibit a discernable increase with use of bio- these soils become mandatory to restore and
fertilizers (Dar and Bali, 2007). Afzal, (2006) maintain the effective microbial populations
found that seed and straw yield of green for solubilization of chemically fixed
gram increased significantly up to single phosphorus and availability of other macro
inoculation with Rhizobium under 20 kg N + and micronutrients to harvest good
45 kg P2O5 ha-1 fertility level. Field trials sustainable yield of various crops.
carried out in different locations have Commercial exploitation of phosphatic
demonstrated that under certain microbial inoculants can play an important
environmental and soil conditions role particularly in making the direct use of
inoculation with azotobacteria has beneficial abundantly available low grade phosphate

7. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
possible. Among the bacterial genera with consists of a wider physical exploration of
this capacity are pseudomonas, Bacillus, the soil by mycorrhizal fungi (hyphae) than
Rhizobium, Burkholderia, Achromobacter, by roots. A speculative mechanism to explain
Agrobacterium, Microccocus, Aereobacter, P uptake by mycorrhizal fungi involves the
Flavobacterium and Erwinia. production of glomalin. Glomalin contains
Beside N-fixation and P-solubilization, very substantial amounts of iron (up to 5% of
the incorporation of nitrogen fixing bacteria the glomalin pool, Lovelock et al., 2004).
(Azotobacter spp.) under the commercial Assuming 0.5 mg glomalin g-1 soil with 1%
name ‘cerealien’ and phosphate dissolving iron, and assuming that this iron was
bacteria (Bacillus megaterium) ‘phosphorien’ derived initially from unavailable Fe–P
has shown the highest degree in inducing the forms in the NaOH-Pi fraction, the
degree of the physiological tolerance to destabilization of this bond could have
salinity which enables the stressed plants of released 1.75 mg P per pot, comparable to the
the Seets cultivar of wheat to be adapted and 2.01 mg NaOH-Pi that was taken up. Bolan et
keep better performance against all applied al. (1987) had already proposed that
levels of salinity (3000, 6000 and 9000 ppm). mycorrhizal fungi may break the bond
This performance was reflected by the between Fe and P, but they did not suggest a
increase in growth, dry matter accumulation, mechanism. Further research into the
yield as well as chemical constituents. All physiological and ecological roles of
chemicals constituents including N, P, K+, glomalin is needed to address this question.
sugars, proline and were increased as AM plants have been reported to improve
compared to their control treatments in the nutrition of the other macronutrients N and
cultivar Seets. Mohmoud and Mohamad, K. In acid soils, AM fungi may be important
2008. for the uptake of ammonium (NH4+), which
Mycorrhizae is less mobile than nitrate (NO3-) and where
The fungi that are probably most diffusion may limit its uptake rate. Although
abundant in agricultural soils are arbuscular nitrate is much more mobile than
mycorrhizal (AM) fungi. They account for 5– ammonium (uptake is regulated through
50% of the biomass of soil microbes (Olsson mass flow). Because of their small size, AM
et al., 1999). Biomass of hyphae of AM fungi fungal hyphae are better able than plant
may amount to 54–900 kg ha-1 (Zhu and roots to penetrate decomposing organic
Miller, 2003), and some products formed by material and are therefore better competitors
them may account for another 3000 kg for recently mineralized N (Hodge, 2003). By
(Lovelock et al., 2004). Pools of organic capturing simple organic nitrogen
carbon such as glomalin produced by AM compounds, AM fungi can short-circuit the
fungi may even exceed soil microbial N-cycle.
biomass by a factor of 10–20 (Rillig et al., It is also reported that the AM- fungi also
2001). The external mycelium attains as increases the uptake of K, and concentration
much as 3% of root weight (Jakobsen and of K has been found more in mycorrhizal
Rosendahl, 1990). Approximately 10–100 m than non-mycorrhizal plants (Bressan et al.,
mycorrhizal mycelium can be found per cm 2001). Apart from this, the AM-fungi also
root (McGonigle and Miller, 1999). increases the uptake and efficiency of
The mineral acquisition from soil is micronutrients like Zn, Cu, Fe etc. by
considered to be the primary role of secreting the enzymes, organic acids which
mycorrhizae, but they play various other makes fixed macro and micronutrients
roles as well which are of utmost important: mobile and as such are available for the
plant.
Improved nutrient uptake (Macro and
micronutrients) Better water relation and drought tolerance
The improvement of P nutrition of plants AM fungi play an important role in the
has been the most recognized beneficial water economy of plants. Their association
effect of mycorrhizas. The mechanism that is improves the hydraulic conductivity of the
generally accepted for this mycorrhizal role

8. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
root at lower soil water potentials and this hyphae of the latter over those of AM fungi
improvement is one of the factors (Klironomos and Kendrick, 1996; Gange,
contributing towards better uptake of water 2000). In addition, AM fungi produce
by plants. Also, leaf wilting after soil drying, glomalin (12-45 mg/cm3), a specific soil-
did not occur in mycorrhizal plants until soil protein, whose biochemical nature is still
water potential was considerably lowered unknown. Glomalin is quantified by
(approx. 1.0 M. Pa). Leaflets of Leucaena measuring several glomalin related soil-
plants inoculated with VA mycorrhizae did protein (GRSP) pools (Rillig, 2004). Glomalin
not wilt at a xylem pressure potential as low has a longer residence time in soil than
as -2.0 MPa. Mycorrhiza induced drought hyphae, allowing for a long persistent
tolerance can be related to factors associated contribution to soil aggregate stabilization.
with AM colonization such as improved leaf The residence time for hyphae is considered
water and turgor potentials and maintenance to vary from days to months (Staddon et al.,
of stomatal functioning and transpiration, 2003) and for glomalin from 6 to 42 years
greater hydraulic conductivities and (Rillig et al., 2001). Steinberg and Rillig (2003)
increased root length and development. demonstrated that even under relatively
favorable conditions for decomposition, 40%
Soil structure (A physical quality) of AM fungal hyphae and 75% of total
Whereas the role of mycorrhizal glomalin could be extracted from the soil 150
associations in enhancing nutrient uptake days after being separated from their host.
will mainly be relevant in lower input agro- Glomalin is considered to stably glue hyphae
ecosystems, the mycorrhizal role in to soil. The mechanism is the formation of a
maintaining soil structure is important in all ‘sticky’ string-bag of hyphae which leads to
ecosystems (Ryan and Graham, 2002). the stability of aggregates.
Formation and maintenance of soil structure
will be influenced by soil properties, root Enhanced phytohormone activity
architecture and management practices. The activity of phytohormones like
The use of machines and fertilizers are cytokinin and indole acetic acid is
considered to be responsible for soil significantly higher in plants inoculated with
degradation. The specific adsorption of P by AM. Higher hormone production results in
functional groups can affect the charge better growth and development of the plant.
balance and cause dispersion of particles
(Lima et al., 2000). Soil aggregation is one Crop protection (Interaction with soil
component of soil structure. Mycorrhizal pathogens)
fungi contribute to soil structure by (1) AM fungi have the potential to reduce
growth of external hyphae into the soil to damage caused by soil-borne pathogenic
create a skeletal structure that holds soil fungi, nematodes, and bacteria. Meta-
particles together; (2) creation by external analysis showed that AM fungi generally
hyphae of conditions that are conducive for decreased the effects of fungal pathogens. A
the formation of micro-aggregates; (3) variety of mechanisms have been proposed
enmeshment of micro aggregates by external to explain the protective role of mycorrhizal
hyphae and roots to form macro aggregates; fungi. A major mechanism is nutritional,
and (4) directly tapping carbon resources of because plants with a good phosphorus
the plant to the soils (Miller and Jastrow, status are less sensitive to pathogen damage.
1990, 2000). This direct access will influence Non-nutritional mechanisms are also
the formation of soil aggregates, because soil important, because mycorrhizal and non-
carbon is crucial to form organic materials mycorrhizal plants with the same internal
necessary to cement soil particles. Hyphae of phosphorus concentration may still be
AM fungi may be more important in this differentially affected by pathogens. Such
regard than hyphae of saprotrophic fungi non-nutritional mechanisms include
due to their longer residence time in soil, activation of plant defense systems, changes
because fungivorous soil fauna prefers in exudation patterns and concomitant

9. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
changes in mycorrhizosphere populations, sterilization (while using autoclave, lime
increased lignification of cell walls, and mixed lignite is filled up to two third
competition for space for colonization and capacity of steel trays for 1-2 hours for three
infection sites (Kaisamdar, et al. 2001). It is days and sterilized at 121 0C ) for carrier
also reported that increased production and material.
activity of phenolic and phytoalexien
compounds with due to AM-inoculation Mutation during fermentation
considerably increases the defense Bio-fertilizers tend to mutate during
mechanism there by imparts the resistance to fermentation and thereby raising production
plants. and quality control cost. Extensive research
work on this aspect is urgently needed to
4. Constraints in bio-fertilizer use eliminate such undesirable changes.
Production Constraints
Despite significant Market level constraints
improvement/refinement in BF technology Lack of awareness of farmers
over the years, the progress in the field of BF Inspite of considerable efforts in recent
production technology is below satisfaction years, majority of farmers in India are not
due to the followings:- aware of bio-fertilizers, their usefulness in
increasing crop yields sustainably.
Unavailability of appropriate and efficient
strains Inadequate and Inexperienced staff
Lack of region specific strains is one of Because of inadequate staff and that too
the major constraints as bio-fertilizers are not not technically qualified who can attend to
only crop specific but soil specific too. technical problems. Farmers are not given
Moreover, the selected strains should have proper instructions about the application
competitive ability over other strains, N- aspects.
fixing ability over a range of environmental
conditions, ability to survive in broth and in Lack of quality assurance
inoculants carrier. The sale of poor quality bio-fertilizers
through corrupt marketing practices results
Unavailability of suitable carrier in loss of faith among farmers, to regain the
Unavailability of suitable carrier (media faith once is very difficult and challenging.
in which bacteria are allowed to multiply)
due to which shelf life of bio-fertilizers is Seasonal and unassured demand
short is a major constraint. Peat of a good The bio-fertilizer use is seasonal and
quality (more than 75% carbon) is a rare both production and distribution is done
commodity in India. Nilgiri peat is of poor only in few months of year, as such
quality (below 50% carbon). According to the production units particularly private sectors
availability and cost at production site, are not sure of their demand.
choice is only with lignite and charcoal in
India. As per the suitability the order is peat Resource constraint
>lignite > charcoal > FYM > soil >rice husk. Limited resource generation for BF
production
Good quality carrier must have good
The investment in bio-fertilizer
moisture holding capacity, free from toxic
production unit is very low. But keeping in
substances, sterilisable and readily adjustable
view of the risk involved largely because of
PH to 6.5-7.0. Under Indian conditions where
short shelf life and no guarantee of off take of
extremes of soil and weather conditions
bio-fertilizers, the resource generation is very
prevail, there is yet no suitable carrier
limited.
material identified capable of supporting the
growth of bio-fertilizers. Better growth of
bacteria is obtained in sterile carrier and the
Field level constraints
best method is Gamma irradiation of
Soil and climatic factors

10. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
Among soil and climatic conditions, high based bio-fertilizers (1000 times). Since these
soil fertility status, unfavorable PH, high are liquid formulations the application in the
nitrate level, high temperature, drought, field is also very simple and easy. They are
deficiency of P, Cu, Co, Mo or presence of applied using hand sprayers, power
toxic elements affect the microbial growth sprayers, fertigation tanks and as basal
and crop response. manure mixed along with FYM etc.
Native microbial population
Antagonistic microorganism already 5. Conclusion and future strategies
present in soil competes with microbial Identification/ selection of efficient
inoculants and many times do not allow location/ crop/soil specific strains
their effective establishment by out- for N-fixing, P, Zn- solubilizing and
competing the inoculated population. absorbing (mycorrhizal) to suit
Faulty inoculation techniques different agro climatic conditions.
Majority of the marketing sales Strain improvement through
personals do not know proper inoculation biotechnological methods.
techniques. Bio-fertilizers being living Exchanging the cultures between
organisms required proper handling, countries of similar climatic
transport and storage facilities. conditions and evaluating their
performance for better strain for
Liquid Bio-fertilizers (Break through in BF- particular crop. Checking the activity
Technology) of cultures during storage to avoid
Liquid bio-fertilizers are special liquid natural mutants.
formulation containing not only the desired Use of sterile carriers and installing
microorganisms and their nutrients but also centralized unit of gamma chamber
special cell protectants or chemicals that facilities at different locations to use
promote formation of resting spores or cysts by private and government
for longer shelf life and tolerance to adverse manufacturers in the case of use of
conditions. (Hegde, 2008). carrier based inoculants till the
Bhattacharyya and Kumar (2000), states development of alternate formulation.
that, bio-fertilizers manufactured in India are Identifying two or three common
mostly carrier based and in the carrier-based carrier materials in different
(solid) bio-fertilizers, the microorganisms countries based on availability and
have a shelf life of only six months. They are recommends them to the producers.
not tolerant to UV rays and temperatures Developing suitable alternate
more than 30 0C. The population density of formulations viz., liquid inoculants /
these microbes is only 108 (10 crores) c.f.u/ml granular formulations for all
at the time of production. This count reduces bioinoculants, to carrier based
day by day. In the fourth month it reduces to inoculants. Standardizing the media,
106 (10 lakhs) c.f.u/ml and at the end of 6 method of inoculation etc., for the
months the count is almost nil. That’s why new formulations.
the carrier-based bio-fertilizers were not Employing microbiologists in
effective and did not become popular among production units to monitor the
the farmers. These defects are rectified and production. Developing cold storage
fulfilled in the case of Liquid bio-fertilizers. facilities in production centers.
The shelf life of the microbes in these liquid Technical training on the production
bio-fertilizers is two years. They are tolerant and quality control to the producers
to high temperatures (55 0C) and ultra violet and rendering technical advice and
radiations. The count is as high as projects to manufacturers.
109 c.f.u/ml, which is maintained constant Organizational training to the
up to two years. So, the application of 1 ml of extension workers and farmers to
liquid bio-fertilizers is equivalent to the popularize the technology.
application of 1 Kg of 5 months old carrier Dissemination of information

11. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
through mass media, publications on wheat development. J. Agronomy Crop Sci.,
and bulletins. 175: 119-127.
Emam N.F., Fayez M., Makboul H.E. 1986. Wheat
Referenes growth as affected by inoculation with
Anonymous, 2008. Data on bio-fertilizer production Azotobacter isolated from different soils.
and demand, maintained by deptt. Of fertilizers, Zentralbl. Microbiol., 141: 17-23.
Ministry of chemical and fertilizers, India. Based Fares C.N. (1997). Growth and yield of wheat plant
upon information received from State as affected by biofertilisation with associative,
Govt., Regional centers/NGO. symbiotic N2-fixers and endomycorrhizae in the
Afzal, M. 2006. Effect of Rhizobium, PSB with presence of the different P-fertilizers. Ann. Agr.
different fertility levels on green gram under Sci., 42: 51-60.
temperate conditions of Kashmor. P.G.Thesis Gange, A., 2000. Arbuscular mycorrhizal fungi.
results, pp103-104. Collembola and plant growth. Trends Ecol.Evol.
Alloway, B.J. 2008. Zinc in soils and crop nutrition. 15, 369–372.
Second edition, IZA and IFA publishers, Godara R.K., Awasthi R.P., Kaith N.S. 1995. Effect of
Brussels, Belgium and Paris, France. Pp.21-22. biofertilizer and fetilizer on Azotobacter
Arun K.S. 2007. Bio-fertilizers for sustainable population, crown gall infection and alkaline
agriculture. Mechanism of P-solubilization. phosphatase activity in peach. Indian J. Plant
Sixth edition, Agribios publishers, Jodhpur, Physiol., 38: 334-336.
India, pp.196-197. Hegde, S.V. 2008. Liquid bio-fertilizers in Indian
Bhat, M.I., Rashid, A., Rasool, F., Mahdi, S.S., Haq, agriculture. Bio-fertilizer news letter, pp.17-22.
S.A. and Bhat, R.A. 2010. Effect of Hodge, A., 2003. Plant nitrogen capture from organic
Rhizobium and VA-mycorrhizae on green gram matter as affected by spatial dispersion,
under temperate conditions. Research Journal of interspecific competition and mycorrhizal
Agricultural Sciences, 1(2): 113-116. colonization. New Phytol. 157, 303–314.
Bhatttacharyya, P. and Kumar, R. 2000. Liquid Hussain A., Arshad M., Hussain F. (1987). Response
biofertilizer-current Knowledge and Future of maize (Zea Mays) to Azotobacter inoculation.
prospect. National seminar on development and Biol. Fert. Soils, 4: 73-77.
use of biofertilizers, biopesticides and organic Jakobsen, I., Rosendahl, L., 1990. Carbon flow into
manures. Bidhan Krishi Viswavidyalaya, soil and external hyphae from roots of
Kalyani, West Bengal, November 10- 12. mycorrhizal cucumber roots. New Phytol. 115,
Biswas, B.C. Yadav, D.S., and Satish Maheshwari, 77–83.
1985. Bio-fertilizers in Indian Agriculture. Kachroo, D. and Razdan, R. 2006. Growth, nutrient
Fertilizer News 30(10): 20-28. uptake and yield of wheat (Triticum aestivum) as
Bolan, N.S., Robson, A.D., Barrow, N.J., 1987. Effects influenced by biofertilizers and nitrogen. Indian
of vesicular–arbuscular mycorrhiza on the Journal of Agronomy 51 (1): 37-39.
availability of iron phosphates to plants. Plant Kannaiyan, S.1990. Blue green algae biofertilizers.
Soil 99, 401–410. The biotechnology of biofertilizers for rice crops.
Bressan, W., Siqueira, J.O., Vasconcellos, C.A., (ed) S. Kannaiyan, Tamil Nadu Agric.
Purcino, A.A.C., 2001. Fungos micorrizicos e University publications, Coimbatore,
fosforo, no crescimento, nos teores de nutrients T.N.India.pp.225.
e na produc¸ao do sorgo e soja consorciados. Kasiamdari, R.S., Smith, S.E., Smith, F.A., Scott, E.S.,
Pesqui. Agropecu. Bras. 36, 315–323. 2001. Influence of the mycorrhizal fungus,
Dar, N.A. and Bali, A.S. 2007. Influence of bio- Glomus coronatum, and soil phosphorus on
fertilizers and nitrogen levels on transplanted infection and disease caused by binucleate
rice
(Oryza sativa L.) under temperate agro-climatic Rhizoctonia and Rhizoctonia solani on mung
conditions of Jammu and Kashmir. Journal of bean (Vigna radiata). Plant Soil 238, 235–244.
Research, SKUAST-J, 6 (1): 67-72. Katyal, J.C. and Rattan, R.K. 1993. Distribution of
Elgala A.M., Ishac Y.Z., Abdel Monem M., zinc in Indian soils. Fertilizer News 38 (6):
ElGhandour I.A.I. (1995). Effect of single and 15-26.
combined inoculation with Azotobacter and VA Katyal, J.C., Venkatashwarlu, B., and Das, S.K. 1994.
micorrhizal fungi on growth and mineral Biofertilizer for Nutrient Supplementation
nutrient contents of maize and wheat plants. In: in Dryland Agriculture. Fertiliser News
Huang P.M., Berthelin J., Bollag J.M., Mcgill 39(4): 27-32.
W.B., Page A.L.,eds, Environmental Impact of Klironomos, J.N., Kendrick, B., 1996. Palatability of
Soil Component Interaction, Vol. 2: Metals, micro fungi to soil arthropods in relation to the
Other Inorganics, and Microbial Activities, PP. functioning of arbuscular mycorrhizae. Biol.
109-116. Fertil. Soils 21, 43–52.
Elshanshoury A.R. 1995. Interaction of Azotobacter Lima, J.M., Anderson, S.J., Curi, N., 2000. Phosphate
chroococcum, Azospirillum brasilense and induced clay dispersion as related toaggregate
Streptomyces mutabilis, in relation to their effect

12. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
size and composition in Hapludoxs. Soil Sci. Soc. growth substances produced by the diazotrophs.
Am. J. 64, 892–897. Microbiological Research, 150: 121-127.
Lovelock, C.E., Wright, S.F., Clark, D.A., Ruess, Radwan F.I. 1998. Response of some maize cultivars
R.W., 2004. Soil stocks of glomalin produced to VA – mycorrhizal inoculation, biofertilization
by arbuscular mycorrhizal fungi across a and soil nitrogen application. Alexandria Journal
tropical rain forest landscape. J. Ecol. 92, 278– of Agricultural Research, 43: 43-56.
287. Raghu K, Macrae IC. 2000. Occurrence of
Mahdi, S.S., S. A. Dar, S. Ahmad and G.I. Hassan. phosphate-dissolving microorganisms in the
2010. Zinc availability- A major issue in rhizosphere of rice Plants and in submerged
agriculture. Research Journal Agricultural soils. J. Appl. Bacteriol 29:582–6.
Sciences, 3(3): 78-79. Rai S.N., Gaur A.C. 1988. Chraracterization of
Mandhare V.K., Patil P.L., Gadekar D.A. 1998. Azotobacter spp. and effect of Azotobacter and
Phosphorus uptake of onion as influenced by Azospirillum as inoculant on the yield and N –
Glomus fasciculatum, Azotobacter and phosphorus uptake of wheat crop. Plant Soil, 109: 131-134.
levels. Agricultural Science Digest, 18: 228-230. Remesh, P. 2008. Organic farming research in M.P.
Martinez Toledo M.V., Gozalez-Lopez J., De la Rubia Organic farming in rain fed agriculture: Central
T., Moreno J., Ramos-Cormenzana A. 1988. institute for dry land agriculture, Hyderabad,
Effect of inoculation with Azotobacter pp-13-17.
chroococcum on nitrogenase activity of Zea mays Ryan, M.H., Graham, J.H., 2002. Is there a role for
roots grown in agricultural soils under aseptic arbuscular mycorrhizal fungi in production
and non-sterile conditions. Biol. Fert. Soils, 6: agriculture. Plant Soil 244, 263–271.
170-173. Raj. S. A. 2007. Bio-fertilizers for micronutrients. Bio-
McGonigle, T.P., Miller, M.H., 1999.Winter survival fertilizer Newsletter (July), pp 8-10.
of extra radical hyphae and spores of arbuscular Rillig, M.C., Wright, S.F., Nichols, K.A., Schmidt,
mycorrhizal fungi in the field. Appl. Soil Ecol.12, W.F., Torn, M.S., 2001. Large contribution of
41–50. arbuscular mycorrhizal fungi to soil carbon
Mahmoud, A.A. and Mohamed, Hanna FY. 2008. pools in tropical forest soils. Plant Soil 233, 167–
Impact of biofertilizers application on 177.
Improving Wheat (Triticum aestivum L.) Rillig, M.C., 2004. Arbuscular mycorrhizae and
resistance to Salinity. Research journal of terrestrial ecosystem processes. Ecol. Lett. 7, 740–
agriculture and biological science, 4(5): 520-528. 754.
Miller, R.M., Jastrow, J.D., 1990. Hierarchy of root Roger, P.A., and Ladha J.K. 1992. Biological N2
and mycorrhizal fungal interactions with soil fixation in wetland rice fields: estimation and
aggregation. Soil Biol. Biochem. 22, 579–584. contribution to nitrogen balance. Plant Soil
Miller, R.M., Jastrow, J.D., 2000. Mycorrhizal fungi 141:41-5.
influence soil structure. In: Kapulnik, Y., Douds, Sabashini H.D., Malarvannan S. and Kumar P. 2007.
D.D. (Eds.), Arbuscular Mycorrhizas: Effect of biofertilizers on yield of rice cultivars
Physiology and Function. Kluwer Academic, in Pondicherry, India. Asian Journal of
Dordrecht, pp. 3–18. Agriculture Research 1(3): 146-150.
Mishra O.R., Tomar U.S., Sharama R.A., Rajput A.M. Sawers, J.H. Caroline, G. and Paszkowski, U. 2007.
1995. Response of maize to chemicals and A study about cereal mycorrhiza, an ancient
biofertilizers. Crop Research, 9: 233-237. symbiosis in modern Agricuture. Department of
Mosse, B., Stribley, D.P., and Le Tacon, F. 1981. Plant Molecular Biology, University of
Ecology of mycorrhizae and mycorrhizal fungi. Lausanne, Biophore Building, Lausanne,
Advance in Microbial Ecology 5:137-210. Switzerland.
Nieto K.F. and Frankenberger W.T. 1991. Influence Son, T.N., Thu, V.V., Duong, V.C. and Hiraoka, H.
of adenine, isopentyl alcohol and Azotobacter 2007. Effect of organic and bio-fertilizers on
chroococcum on the vegetative growth of Zea soybean and rice cropping system. Japan
mays. Plant Soil, 135: 213-221. International Research Center for Agricultural
Olsson, P.A., Thingstrup, I., Jakobsen, I., Baath, E., Sciences, Tsukuba, Ibaraki, Japan.
1999. Estimation of the biomass of arbuscular Staddon, P.L., Bronk Ramsey, C., Ostle, N., Ineson,
mycorrhizal fungi in a linseed field. Soil Biol. P., Fitter, A.H., 2003. Rapid turnover of hyphae
Biochem. 31, 1879–1887. of mycorrhizal fungi determined by AMS
Pandey A., Sharma E., Palni L.M.S. 1998. Influence of microanalysis of 14C. Science 300, 1138–1140.
bacterial inoculation on maize in upland Steinberg, P.D., Rillig, M.C., 2003. Differential
farming system of the Sikkim Himalaya. Soil decomposition of arbuscular mycorrhizal fungal
Biol. Biochem., 30: 379-384. hyphae and glomalin. Soil Biol. Biochem. 35, 191–
Pati B.R., Sengupta S., Chjandra A.K. 1995. Impact of 194.
selected phyllospheric diazotrophs on the Subba Roa, N.S. 2001. An appraisal of biofertilizers
growth of wheat seedlings and assay of the in India. The biotechnology of biofertilizers,

13. S. Sheraz Mahdi et al./J Phytol 2/10 (2010) 42-54
(ed.) S.Kannaiyan, Narosa Pub. House,
New Delhi (in press).
Tippannavar C.M., Reddy T.K.R. 1993. Seed
treatment of wheat (Triticum aesativum L.) on the
survival of seed borne Azotobacter chroococcum.
Karnataka Journal of Agricultural Sciences, 6: 310-
312.
Venkataraman, G.S. and Shanmugasundaram, S.
(1992). Algal biofertilizers technology for rice.
DBT Centre for BGA. Bio-fertilizer, Madurai
Kamraj University, Madurai, 625021, T.N.
1-24.
Venkatashwarlu, B. 2008. Role of bio-fertilizers in
organic farming: Organic farming in rain fed
agriculture: Central institute for dry land
agriculture, Hyderabad.pp. 85-95.
Wani, S.P. and Lee K.K. 2002. Population dynamics
of nitrogen fixing bacteria associated with pearl
millet (P. americanum L.). In biotechnology of
nitrogen fixation in the tropics. University of
Pertanian, Malaysia, 21-30.
Wani, S.P. and Lee, K.K. 1995. Microorganisms as
biological inputs for sustainable agriculture in
Organic Agriculture (Thampan, P.K.ed.) Peekay
Tree Crops Development Foundation, Cochin,
India. Pp-39-76.
Zhu, Y.G., Miller, R.M., 2003. Carbon cycling by
arbuscular mycorrhizal fungi in soil—plant
systems. Trends Plant Sci. 8, 407–409.