Black-eyed peas, or cowpeas, obtain much of their nitrogen through a partnership with soil bacteria. University of California, Riverside research examined whether modern crop breeding had weakened that useful relationship—and found the plants still retained substantial capacity to benefit from it.
How biological nitrogen fixation works
Cowpea roots release chemical signals that attract rhizobia. The plant forms nodules that provide the bacteria with carbon and a protected environment; in return, the bacteria convert atmospheric nitrogen into forms the plant can use.
The experiment compared 20 cowpea types and found modern varieties were not generally less able to attract and benefit from rhizobia than their wild ancestors. Some lines appeared to gain even more benefit, suggesting there may be a genetic basis that breeders can select for.
Implications for fertiliser and rotations
After a legume dies, part of the associated microbial community and plant nitrogen remains in the system. Rotating legumes with other crops can therefore support soil nitrogen cycling and reduce, though not automatically eliminate, the need for manufactured fertiliser.
The findings point toward crop genetics and microbial services as tools for more efficient agriculture. They do not mean every following crop can be grown without fertiliser: the result depends on biomass, harvested nitrogen, soil conditions, rhizobial strains and the needs of the next crop. Field testing and nutrient budgeting remain essential.
Read the original report: The Independent.