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E-International Scientific Research Journal
ISSN: 2094-1749 Volume: 3 Issue: 2, 2011
Biofertilizers in Action: Contributions of BNF in Sustainable
Agricultural Ecosystems
A.M., Ellafi, 1 Gadalla, A 2 and Galal 2 , Y.G.M.
1 Biotechnology Research Center, Tripoli, Libya
2Atomic Energy Authority, Nuclear Research Center, Soil and Water Research Department,
Abou-Zaabl, 13759, Egypt.
Abstract
Biofertilizers are considered to be cost effective, ecofriendly and renewable sources of plant
nutrients supplementing chemical fertilizers in sustainable agricultural systems. This refers to
microorganisms, which increase crop growth through different mechanisms, i.e. biological
nitrogen fixation, growth-promoting or hormonal substances increased availability of soil
nutrients. Their importance lies in their ability to supplement/ mobilize soil nutrients with
minimal use of non-renewable resources and as components of integrated plant nutrient systems.
The most important group of biofertilizers that have played vital role of maintaining soil fertility
in agriculture via BNF process. Contributions of BNF through the application of different
nitrogen fixing microorganisms (biofertilizers groups) were estimated under different
environmental conditions given using isotopic ( 15 N isotope dilution) and non-isotopic (N
difference) methods. Symbiotic plant-microbe interactions such as Rice-Azolla, Legume-
Rhizobium either prennial crops or fixing trees were examined on field and greenhouse
experiments. Similarly, free-living or associative N 2 fixing microorganisms were evaluated for
potential N 2 fixation with non-legumes, i.e. rice, maize, barely and wheat. Also, growthpromoting
effect was considered for plants, particularly cereal crops inoculated with
diazotrophs and/or arbuscular mycorrhiza fungi (VAM). Such microflora have the ability to
provide considerable amounts of sparing nutrients especially P in rhizoplane of inoculated
plants. Application of 15 N tracer techniques gave us a chance to confirm some of the mechanisms
responsible for enhancement of plant growth and nutrient acquisition. From our viewpoint, it is
important to encourage the use of biofertilizers especially under circumstances of lacks in soil
and water resources like we have in our region and in the same time, to spread out the concept
of low input agriculture to the poor farmers. Therefor, there is a need to develop reliable
biofertilizers with scientifically defined modes of action and incorporating BNF to maximize
their efficacy.
Keywords: Agro-ecosystems, Biofertilizers, BNF, Isotopic techniques
Introduction
Beneficial plant-microbe interactions in the rhizosphere are primary determinants of plant health
and soil fertility. Various soil microorganisms that are capable of exerting beneficial effects on
plants have a potential for use in agriculture and can lead to increased yields of a wide variety of
crops. Soil-plant-microbe interactions are complex and there are many ways in which the
outcomes can influence plant health and productivity (Kennedy 1998). Microbial groups that
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