Comparision of Five Carriers of Sinorhizobium meliloti to Produce Alfalfa Inoculant

Peat is the best known and the most widely used rhizobial carrier, but unfortunately, it lacks of sufficient sources in Iran. This research aimed at using some inexpensive materials as carrier instead of peat for producing the rhizobial inoculant for alfalfa. For this purpose, the physical and chemical properties of some materials to be used as carriers were determined and the viability of Sinorhizobium meliloti on these carriers during 6 months at +4 ºC was evaluated. The selected carriers were 1) Peat (control) 2) Vermicompost 3) Bilogical Filter Waste (BFW) 4) Vermiculite+Vermicompost (1:1w/w), and 5) Vermiculite+BFW (1:1w/w). Also to determine the suitable moisture content of carriers on prolongation of bacterial survival, two matric potential levels including –10 and –30 kpa were applied on the carriers. The results showed that vermiculite+BFW (1:1w/w) not only maintained a standard number of bacteria compared to the other treatment, but also caused good nodulation on alfalf seedling at the end of the 6th month. Although BFW carrier maintained a high number of bacteria after six months storage, it can not be recommended as a suitable carrier because of its negative effect on nodulation. In this study, higher number of bacteria was maintained in the matric potential of –30 kpa than –10kpa.