Beans fix nitrogen that feeds the corn growing beside them, that season.
Confidence in this refutation: A good hunch
This is one the planner refuses to enforce. The claim is recorded here with what is actually known, rather than dropped — a rule that was checked and failed is worth more to you than one that was never checked.
What is actually known
Rhizobia in legume root nodules do fix atmospheric N. Most of it is incorporated into the legume's own tissue. Some does move to a neighbouring non-legume the same season via direct root contact and rhizodeposition, but the amount is small — a few percent of the neighbour's N uptake — and does not meet a heavy feeder's demand. The bulk of the benefit arrives the following season, after residues decompose.
Beans will improve this ground for next year. They will not feed your corn this year.
The evidence
Evidence: confirmed against 3 sources in the research-based literature.
the 3 sources
Univ. of Arkansas Extension, 'Creating a Three Sisters Garden', uaex.uada.edu (read 2026-07-11): 'Most of the nitrogen converted by the beans will not be available to the corn and pumpkins the first year; the bean roots have to break down to release nitrogen. Corn is a heavy nitrogen [feeder].'
Hupe et al. 2021, Sci Rep 11:11424, 'Evidence of considerable C and N transfer from peas to cereals via direct root contact but not via mycorrhiza', pmc.ncbi.nlm.nih.gov/articles/PMC8169652 (read 2026-07-11): reports 'a mean N transfer rate of 8.4%, with a range of 2.7 to 22.5%, ... from N2-fixing legumes to non-N2-fixing mycorrhizal cereals' and 'N transfer rates of between 3.1 and 6.0% ... from soybean to maize'.
'Nitrogen uptake and transfer in a soybean/maize intercropping system in the karst region of southwest China', pmc.ncbi.nlm.nih.gov/articles/PMC5648690 (read 2026-07-11): 'N transferred from soybean to maize account for 2.4%–3.3% of the N uptake of maize.'