Can manure application method and timing with cover crops reduce NH₃ and N₂O gas losses and sustain corn yield?

Ammonia (NH 3 ) loss following manure application is an environmental concern and N loss for crop production. Manure injection typically reduces NH 3 loss compared to surface application without incorporation but increases emissions of nitrous oxide (N 2 O), which is a potent greenhouse gas. Synchronizing manure in spring with cover crop (CC) growth may increase N recovery and reduce N 2 O emissions compared to applying manure later in the absence of growing crops. We compared the two following manure application methods: shallow‐disk injection (IM) or surface banding without incorporation (BM) to annual ryegrass ( Lolium multiflorum L.) and red clover ( Trifolium pratense L.) CC at two times: early spring on growing CC (EARLY) and late spring on terminated CC (LATE). The randomized split‐plot block experiment was conducted at Rock Springs, PA, during 2021–2022. After manure application, we measured NH 3 for 72 h and N 2 O throughout the growing season. Aboveground CC biomass, N, and C:N ratio; pre‐sidedress soil nitrate; corn ( Zea mays L.) stalk nitrate; and silage yield were assessed. Averaged across application times, compared to BM, IM reduced cumulative NH 3 loss, increased soil N, and resulted in 13% greater corn yield but increased yield‐scaled N 2 O. Compared to BM LATE, BM EARLY reduced NH 3 loss by 43%, increased CC N, reduced N 2 O emission by 50%, but decreased corn yield by 11%. When IM was EARLY compared to LATE, CC N increased 84%, cumulative N 2 O loss decreased 55%, and corn yield was similar. Injecting manure to growing CCs offers a strategy for reducing detrimental NH 3 and N 2 O emissions and maintaining corn yield.