Acid soils occur all over the world and have limiting effects on agriculture. One approach to improving production on such soils is to amend them using higher PH materials such as lime or ashes. This can be expensive since large amounts of material need to be spread. Another approach is to select cultivars that tolerate acidity better.

The effect of rhizobial strain and lucerne genotype on the nodulation of lucerne seedlings growing in solution cultures maintained at pH 5 was measured in two greenhouse experiments. . .

The work demonstrates that there remains substantial opportunity to increase the potential of lucerne to nodulate at low pH. Gains would appear to be most easily made by changing the strain of rhizobia that is used for inoculation.

I've often been frustrated by less detail oriented growers who pay little attention to rhizobial strains, considering it a nuisance activity rather than a management control with large potential to affect outcomes. This research supports an idea that matching plant cultivars and microbial symbionts to local conditions can significantly change outcomes for very modest costs.