Dear Ali,

Some biofertilizers are efficient when used for certain plants. For example,  Rhizobiuminoculant is utilized for leguminous crops. Azotobacter can be utilized for crops like wheat, maize, mustard, cotton, potato and other vegetable crops. Azospirillum inoculations are used for sorghum, millets, maize, sugarcane and wheat. Blue green algae belonging to a general cyanobacteria genus, Nostoc or Anabaena or Tolypothrix or Aulosira, fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and low-land conditions. 

For more reading on biofertilizers, please use the following links:

http://www.biotecharticles.com/Agriculture-Article/How-to-Apply-Biofertilizers-603.html

http://www.agnet.org/library.php?func=view&id=20110712070234

http://www.yourarticlelibrary.com/micro-biology/list-of-important-microorganisms-with-practical-application-as-biofertilizers/33576/

https://www.researchgate.net/publication/223544325_Biofertilizers_improve_plant_growth_fruit_yield_nutrition_metabolism_and_rhizosphere_enzyme_activities_of_Pomegranate_Punica_granatum_L_in_Indian_Thar_Desert_Sci_Hortic

http://phys.org/news/2014-10-potential-autochthonous-bacteria-biofertilizers.html

Hoping this will be helpful,

Rafik

Article Biofertilizers improve plant growth, fruit yield, nutrition,...

Hi Ali!

The answer Hani Antoun is a very good. This is a comprehensive, fine the answer.

Best regards.

Yes. Bio-fertilizers are crop specific. 

Endorsing an excellent response fro Prof Hani, i believe , there is need to exploit upon the crop-rhizosphere specific microbial diversity , be it bacterial or mycorrhizal diversity . Time has also come to use the  microorganisms native to that crop  habitat , if favorable response of biofertilization is to be achieved. There are increasing efforts , of late , have given the concept of Microbial Consortium using growth promoters as well as antagonists together , so that plants find much favorable environment to grow under soil borne pathogens free environment . This is the reason , you will find some distinct differences in microbial structural and functional composition within rhizosphere of X-annual crops versus Y-perennial crops.  

Soil microorganisms are host-specific, a good example is the arbuscular mycorrhizal fungi which have formed mycorrhiza with over 80% of plants. Even though the soil usually contains mycorrhiza, called the native mycorrhiza, the microorganisms present may not be the best for its growth and as a biofertilizer. Introducing a new specie (research) then makes this obvious, either to debunk the hypothesis or to accept it. Besides, some microorganisms may adapt well to certain soil conditions, or certain plants that can provide their specific needs.

To give a direct answer to your question, there are "no" specific microorganisms used as biofertilizers for each crop or soil, there are just better options and research, which is a good thing that you have interest in this, keeps unveiling.

Exactly Adebisi ,  without host  plant , there is no specificity of microbes . every plant manufactures the microbes within its rhizosphere according to its metabolic requirements. 

1/ In general biofertilizers efficiency can be effective in an extremly soil condition (salinity, high active Lime and high pH....) . So, their effectiveness is optimum when applied in the transplanted stage early in nursery. In fact, in the rhizosphere, many antagonisms can be caused in the presence of many competitive genotypes. However, if applied in soil, the autochtonious inoculum may give good results if compared with exogenous ones. 

2/ Many commerciallised biofertilzers (mycoorhiza inoculum) are compatible with  large vegetable species . But, their effectiveness is optmum if combined with PGPR (plant growth promting rhizobacteria)

I am not too sure, whether or not , there could be  certain crops capable of enduring one specific community  of microbes , as a indicator microbe for a given crops ..?r

there are specific microorganisms used as bio-fertilizers for each essential micro-nutrients for plant growth.  

Specificity at each level in this case is must for better results, i.e., microbe-crop-soil interaction.

The issue on micronutrients solubilisiing microbes , we have debated at length on same platform few months back . This  discussion would help a great deal in understanding the issue much better. Dr Ghafoor , can you please attach few citations highlighting  specific microbes  aiming at different micronutrients , it will aid a great deal for all of us. 

Hi

Refer to article

The most important constraint limiting crop yield in developing nations worldwide, and especially among resource-poor farmers, is soil infertility. Therefore, maintaining soil quality can reduce the problems of land degradation, decreasing soil fertility and rapidly declining production levels that occur in large parts of the world needing the basic principles of good farming practice. Minerals, organic components and microorganisms are three major solid components of the soil. They profoundly affect the physical, chemical, and biological properties and processes of terrestrial systems. Biofertilizer are the products containing cell of different types of beneficial microorganisms. Thus, biofertilizers can be important components of integrated nutrients management. Organisms that are commonly used as biofertilizers component are nitrogen fixers (N-fixer), solubilizer (K-solubilizer) and phosphorus solubilizer (P-solubilizer), or with the combination of molds or fungi. These potential biological fertilizers would play key role in productivity and sustainability of soil and also protect the environment as eco-friendly and cost effective inputs for the farmers. With using the biological and organic fertilizers, a low input system can be carried out and it can be help achieving sustainability of farms. INTRODUCTION For optimum plant growth, nutrients must be available in sufficient and balanced quantities (Chen, 2006). The most important constraint limiting crop yield in developing nations worldwide, and especially among resource-poor farmers, is soil infertility. Unless the fertility is restored in these areas, farmers will gain little benefit from the use of improved varieties and more productive cultural practices. Soil fertility can be restored effectively through adopting the concept of integrated soil fertility management (ISFM) encompassing a strategy for nutrient management-based on natural resource conservation, biological nitrogen fixation (BNF) and increased efficiency of the inputs (Vlek and Vielhauer, 1994). Biofertilizers are important components of integrated nutrients management. These potential biological fertilizers would play key role in productivity and sustainability of soil and also protect the environment as ecofriendly and cost effective inputs for the farmers. They are cost effective, ecofriendly and renewable source of plant nutrients to supplement chemical fertilizers in sustainable agricultural system. Biofertilizers are products containing living cells of different types of microorganisms which when, applied to seed, plant surface or soil, colonize the rhizosphere or the interior of the plant and promotes growth by converting nutritionally important elements (nitrogen, phosphorus) from unavailable to available form through biological process such as nitrogen fixation and solubilization of rock phosphate (Rokhzadi et al., 2008). Beneficial microorganisms in biofertilizers accelerate and improve plant growth and protect plants from pests and diseases (El-yazeid et al., 2007). The role of soil microorganisms in sustainable development of agriculture has been reviewed (Lee and Pankhurst, 1992; Wani et al., 1995). 

Dear Raheleh

Thank you for interesting answer

best wishes in more success

Ali Alhayany