Background and aims: Crop residue retention and cover cropping are key strategies in conservation agriculture, but their effects on nitrogen (N) cycling and nitrous oxide (N ₂ O) emissions, particularly in semiarid croplands, remain underexplored. This study aimed to evaluate the N dynamics and N ₂ O sources in an irrigated cover crop-maize rotation in central Spain by conducting a ¹⁵ N tracing experiment. Methods: ¹⁵ N-labeled maize ( Zea mays L.) residues were incorporated into the soil, followed by vetch ( Vicia faba L.), barley ( Hordeum vulgare L.) cover crops, or bare fallow. A subsequent maize crop was fertilized with 210 kg N ha ⁻¹ as ammonium nitrate (AN) or ¹⁵ N-labeled AN ( ¹⁵ NH ₄ NO ₃ , ¹⁵ AN//NH ₄ ¹⁵ NO ₃ , A ¹⁵ N) in the microplots receiving ¹⁵ N-enriched or unlabeled maize residues, respectively. Results: Cumulative N ₂ O emissions were 47% higher under vetch than under barley. Average N ₂ O emission factors were 0.05% for ¹⁵ N-labeled residues and 0.23% for fertilizer. Most N ₂ O originated from ¹⁵ AN (42%–61%), followed by endogenous sources (i.e., mineralization of organic N from soil or crop residues, 19%–42%) and A ¹⁵ N (9%–18%). Maize recovered 7.7% of residue N, with no differences between cover cropping treatments. Plant uptake from A ¹⁵ N was 2.3 times higher than from ¹⁵ AN. Across barley, vetch, and fallow, total N recovery averaged 33% in plants and 22% in soil. Barley cover cropping improved fertilizer N recovery in maize by 57% ( P < 0.05) compared with fallow. Conclusion: These findings highlight the role of cereal cover crops and the regulation of ammonium oxidation-based processes in enhancing N use efficiency and reducing fertilizer-derived N ₂ O emissions in semiarid agro-ecosystems.

Publications with shared reference:

0 publications found