Leguminous plants, which bear many beans that are important to humans, are able to grow well in infertile land.
The reason for this is because most legumes have a symbiotic relationship with bacteria, called rhizobia, that can fix nitrogen in the air and then supply the host plant with ammonia as a nutrient.
The plants create symbiotic organs called nodules in their roots. However, if too many root nodules are made it will adversely affect the growth of the plants, because the energy cost of maintaining excessive nodules is too large. Therefore legumes must have a mechanism to maintain the proper number of root nodules, but this system has been poorly understood.