Hi, Prof. Hani Antoun

Thanks for your valuable answer. Now I see how complex the soil is.

My aim is to investigate how different soil microbial communities influence the plants' growing. In order to keep the soil conditions similar, so I decide to re-inoculate the same soils with different communities. 

I know gamma irradiation is the best way to sterilize the soil. However, a large amount of soil is needed for my experiment and I will probably use the autoclave. 

If adding a soil agrees with my objective depends on the proportion of the adding soil to the total soils. If only a small amount of soil is needed to inoculate, then re-inoculating the soil by adding different soils works for my experiment. Do you know what's the normal proportion people used for inoculating?

Best

Dr.Antoun,I appreciate your elaborate reply.Though I am not a professional microbiologist,with  whatever I studied and discussed with colleagues,I believe that microbial diversity exists everywhere and certain microbial communities dominate in a particular agro-ecosystem based on favorable conditions.To say simply, all microorganisms occur every where but their abundance may vary and is governed by growth conditions(temperature, moisture ,soil pH etc.) and availability of carbon and energy sources.Even if a different microbial community is inoculated/transplanted,does it remain same? will it adopt to the new site?Will it become like old microbial diversity in the site?If we bring microbial communities from a Mollisol to an Alfisol or a Vertisol it remain same as Mollisol or transform  like the latter sites?

If using chemical sterilant, its 100% removal from soil will be a difficult task. Inoculating then seems difficult.

Dr. Annangi Subba Rao, I also concern about the question you mentioned. Since my study is a greenhouse study, I'm worried about the contamination of the microbes from the air and the different soil microbial communities may become similar as time goes. Have anybody used re-inoculated soil to grow plant?

 Dr.Wang, to sterilize the soil and inoculate with beneficial organism/organisms  to test their efficacy is a common feature in development of efficient bio-cultures or bio-fertilizers There have been studies on dynamics of microbial communities as affected by fertilizer or herbicide or pesticide applications in agriculture.But I have not come across the studies on replacing of whole microbial communities with new ones brought from elsewhere.It will be interesting study and after inoculation and provision of carbon  for energy and carbon source, the organisms may establish in a short time.

Very nice discussion Dr Wang and  equally thoughtful responses from Prof  Hani as usual  . Its always heartening to read his thought provoking responses. My take on the whole issue is, is it necessary to sterilize the soil to study the responses of re-inoculation on microbial diversity . And , my second take is , a soil in its natural habitat will always maintain a definite microbial diversity while working with a particular crop , this is where rhizosphere is built up for microbial proliference , otherwise in  the absence of crop , i do not think , it will make a viable exercise  for objectives , we are aiming at .  A soil as such will remain the soil only , no rhizosphere , unless crop component is added to facilitate metabolically  active  roots to interact with different  soil components.