Poultry litter application increases N ₂ O emissions but not cover crop residue decomposition in organic corn systems

Abstract

Cover crops provide multiple agroecosystem services, including reducing soil erosion and nitrate (NO ₃ ⁻ ) leaching, increasing carbon (C) sequestration, and supplying biologically fixed nitrogen (N) through legumes. However, combining cover crops with manure‐derived N inputs, a common practice in organic production systems, could aggravate the risks of soil nitrous oxide (N ₂ O) emissions. To determine how cover crop residue and poultry litter interact to influence soil N release and N ₂ O emissions, we conducted a cover crop residue decomposition study during the corn ( Zea mays L.) phase of an organic grain rotation. Nylon mesh litter bags containing a cover crop mixture of triticale [× Triticosecale Wittm.], hairy vetch [ Vicia villosa R.], and winter pea [ Pisum sativum L.] were buried in plots with and without poultry litter. Poultry litter applications did not affect residue decomposition rates or C and N release. However, increasing legume proportion in cover crop mixture from 18% to 34% increased seasonal N release by 74%. Nitrous oxide emissions were significantly greater from cover crop + poultry litter (11.7 N ₂ O‐N kg ha ⁻¹ ) than cover crop alone (2.7 kg N ₂ O‐N ha ⁻¹ ), with greater emissions observed in wetter 2022 than in drier 2023 (10.3 vs. 4 kg N ₂ O‐N ha ⁻¹ ). Nitrous oxide isotopomer and genomic DNA analyses indicated greater N ₂ O contribution from denitrification (57%) than nitrification (43%). Despite higher N ₂ O emissions, the inclusion of poultry litter stabilized corn yield, particularly under drier conditions. These findings highlight the need for improved poultry litter management to balance productivity and N ₂ O mitigation in organic systems.