Nitrogen release and retention tradeoffs diverge across cover crop management practices

Conventional nitrogen (N) management has accelerated N loss from cropland systems due to high fertilizer use and weakened internal N cycling between soil and plant pools. Cover crops may replace some external fertilizer inputs while providing additional soil benefits. However, it is not well understood how cover crop termination management combined with N fertilization modifies N transfer from cover crop residues into cash crops. To quantify cover crop N reuse, we deployed 15 N‐enriched litter and root bags composed of a winter rye ( Secale cereale L.) and pea ( Pisum sativum L.) mix across a field experiment with four N fertilization levels and four termination and weed control treatments: cultivation and disk tillage (CDT), herbicide with disk tillage (HDT), herbicide with no‐till (HNT), and roller crimper with no‐till (RCNT). Litter mass loss rates did not vary across treatments, but more litter N and 15 N were retained under no‐till (RCNT and HNT). Residue‐derived soil and corn N pools were equal across CDT, HDT, and RCNT, but more total residue 15 N was recovered in no‐till treatments. These results suggest more effective transfer and retention of N in intact soil, including with the buried root bags, which saw greater root‐derived 15 N incorporated into corn biomass. Collectively, our data show that N movement diverges among cover crop termination methods, with more conservative movement of cover crop N when soil disturbance is reduced.