Introduction of Rhizobium "hedysari" in alkaline, clay-loam soil by different inoculation techniques.

Seed inoculation is widely used in agriculture, especially for grain legumes. However, it may be suitable for forage legumes too, particularly for the introduction of a new crop or for soil reclamation in marginal areas. This is the case of the present study, aimed at evaluating some strains of Rhizobium sp. (Rhizobium “hedy‐sari “) to inoculate Hedysarum coronarium plants used for reclamation of marginal areas in Tuscany. Strain CC1335, able to produce growth inhibitors in vitro, was able to nodulate the roots both in pot and in all the field inoculation trials, while strain RH19st3 did not enter root system by any inoculation techniques employed. Strains HCNT1 and HCNA, showing detectable competition activity in vitro, produced good nodulation only by using calcium sulphate with the peat‐arabic gum inoculant. The buffering effect of lime played evidently a determinant role in the performance of the inoculant. The results reported here suggest that improved inoculation methods will make possible the utilization of highly nitrogen fixing strains even if unable to compete with indigenous ones. Moreover, the introduction of highly competitive strains, which might interfere with soil microbiota, can be avoided.