Survival of Rhizobium phaseoli in Coal-Based Legume Inoculants

Abstract

The long-term survival of Rhizobium phaseoli strains 127K17, 127K26, and 127K35 in legume inoculants prepared with eight different coals (one strain and one coal per inoculant) was studied. The coals used were Pennsylvania anthracite, bituminous coals from Illinois, Pennsylvania, and Utah, lignite from North Dakota and Texas, and subbituminous coals from New Mexico and Wyoming; they ranged in pH from 4.7 to 7.5 All coals, with the exceptions of Illinois bituminous coal and Texas lignite (pH's of 5.0 and 4.7, respectively), supported the growth and survival of all R. phaseoli strains. All coal-based inoculants in which rhizobial viability was maintained had more than 10 6 rhizobia per g for at least 7 months, and most contained more than 10 7 rhizobia per g after 12 months. It appears that most coals, regardless of grade or source, may be acceptable carriers for R. phaseoli inoculants.