<p>Replacing fallows with winter crops is a sustainable intensification strategy that increases the return of organic residues, which could increase soil organic matter (SOM) content and the efficiency of nitrogen (N) cycling. However, the impacts of winter crops on N availability, N credits, and crop productivity are highly context-specific. This two-year study evaluated the impacts of replacing a winter fallow with chickpea, clover, and rye grown in rotation with corn on coarse-textured soils in Florida (USA), focusing on soil N processes and corn yield by combining traditional soil N measurements, gene abundance, and ¹⁵N tracing under low and high N fertilizer input. Chickpea residues had a low C:N ratio that enhanced the abundance of genes related to N cycling and, along with clover, contributed N credits to corn, as measured through ¹⁵N tracing. However, these N credits were low (&lt; 25&#xa0;kg N ha^-1) and insufficient to consistently improve corn yields when legume winter crops replaced a fallow. Rye had limited effects on soil N cycling or corn responses but had higher recovery of residue ¹⁵N in soil pools than legumes, suggesting that a large fraction of N from rye residues remained in the soil. While high winter crop biomass or increased soil N availability benefitted yield on some occasions, those benefits only occurred under specific crop or N fertilizer conditions. These results highlight the complexity of sustainably intensifying systems and suggest that improvements in soil properties and N cycling may be more evident in the short term than yield gains.</p>