Can manure application method and timing with cover crops reduce ammonia and nitrous oxide gas losses and sustain corn yield

Authors: SIGDEL, SAILSEH - Pennsylvania State University; Dell, Curtis; KARSTEN, HEATHER - Pennsylvania State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2024
Publication Date: 7/20/2024
Citation: Sigdel, S., Dell, C.J., Karsten, H. 2024. Can manure application method and timing with cover crops reduce ammonia and nitrous oxide gas losses and sustain corn yield. Agronomy Journal. 116(5):2242–2262. https://doi.org/10.1002/agj2.21644
DOI: https://doi.org/10.1002/agj2.21644

Interpretive Summary: Injecting manure into soil in no-till cropping systems, where incorporating manure with tillage is not possible, can substantially reduce loss of crop-available nitrogen via ammonia emissions compared to retaining the manure on the soil surface. However, previous research has shown that injection of manure can increase emissions of the potent greenhouse gas nitrous oxide. Spring manure applications are often made after winter cover crops have been terminated with herbicides in preparation for corn planting. Earlier injection of manure into an actively growing cover crop could potentially result in lower nitrous oxide emissions, because the cover crop can immobilize nitrogen that can otherwise be converted to nitrous oxide. A two-year field study in central Pennsylvania showed that both early application of manure to a growing cover crop and later application after cover crop termination substantially reduced ammonia emissions. However, nitrous oxide emissions were approximately 50% lower and yield of the subsequent corn crop was greater with the early manure injection to the growing cover crop. The greater corn yield was likely related to the release of manure-derived nitrogen when cover crop residues decomposed during the corn growing season.

Technical Abstract: Ammonia loss following manure application is an environmental concern and N loss for crop production. Shallow disk manure injection typically reduces NH3 loss compared to surface application without incorporation but may increase nitrous oxide emissions. Synchronizing manure N with crop growth may increase N recovery and reduce nitrous oxide emissions compared to applying manure in the absence of growing crops. We compared two manure application methods: shallow-disk inject (IM) and surface banding without incorporation (BM) to annual ryegrass (Lolium multiflorum L.) and red clover (Trifolium pratense L.) cover crops at two times: early spring on growing cover crops (EARLY) or late spring on terminated cover crops (LATE). The randomized split-plot block experiment was conducted at Rock Springs, PA, during 2021-2022. After manure application we measured ammonia for 72 hours and nitrous oxide throughout the growing season. Aboveground cover crop 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 NH3 loss, increased soil N, resulting in 13% greater corn yield but increasing yield-scaled nitrous oxide by 14%. Compared to BM LATE, BM EARLY reduced ammonia loss 43%, increased cover crop N uptake, and reduced nitrous oxide emission 50%, but decreased corn yield 11%. When IM was EARLY compared to LATE cover crop N uptake increased 84%, cumulative nitrous oxide loss decreased 55%, and corn yield was similar. Injecting manure to growing cover crops offers a potential strategy for reducing ammonia and nitrous oxide emissions and maintaining corn yield.