How did the Rhizobium-legume crop symbioses assume its current important role in world agriculture?

The value of legumes for human food production, as directly consumed (beans, peas, etc.) or indirectly as livestock fodder (alfalfa, clovers, etc.), has been known for a very long time even back to the days of the Roman Empire. Fixing nitrogen directly and freely from the air only added to its agricultural importance. It was not until the late 1800s that a German scientist, H. Hellriegel, reported that peas could only be productively grown when nodules formed on their roots. In quick succession, a Dutch scientist, M.W. Beijerinck, isolated the main causal organism from the nodule that was later called Rhizobium. Once Rhizobium could be isolated and identified the next logical step was for microbiologists to learn to grow the Rhizobia in quantity and for agriculturalists to find out the best way to supply them to the roots of legume plants in a process called “inoculation”. The Nitro-Coat® process is based on the fundamental value of inoculating seed with the correct strain of Rhizobium.