Six different formulations were prepared, using different carrier materials namely; peat moss, mixture of peat moss plus vermiculite 1:2 (w/w), wheat bran, rice husk, clay and sodium alginate. Each carrier material was packed using polyethylene pages, and then divided into three groups. The first group was sterilized by autoclaving at 121˚C for 20 min, the second one was sterilized by gamma irradiation at a dose rate of 4.0 kGy for 1 hour. However the third group was left without sterilization. Half of the inoculated polyethylene bags, containing the tested formulations either sterilized...