In developing countries, adoption of new agricultural technologies is often hampered by a lake of chemical fertilizers. The high cost of chemical fertilizers, nitrogen ones, is often prohibitive to small and marginal farmers. In developed countries, where very high rates of nitrogen fertilizers are used, pollution is often a concern. It is, therefore, important to explore alternative sources of nitrogen to partially meet the nitrogen requirement. Biological nitrogen fixation offers this alternative, and also offers an economically attractive and ecologically sound means of reducing external inputs and improving internal resources. Establishment of new artificial associations, as mentioned before, the nitrogen fixing capacity of symbiotic systems is very significant, but the host and organism specificity of different plant-bacterium association for atmospheric nitrogen fixation is much wider. This feature of the association systems turned attention to creating new artificial system between diazotrophic bacteria and different higher plants. In this context, the aim of the present book was to evaluate whether nitrogen fixing cyanobacteria, specially Nostoc as biofertilizers.