Mitigating nitrogen pollution with under‐sown legume–grass cover crop mixtures in winter cereals. Issue 2 (2nd March 2021)

• Record Type: Journal Article
• Authors: Morris, Andrew H.; Isbell, Sarah A.; Saha, Debasish; Kaye, Jason P.
• Is Part Of: Journal of Environmental Quality. Volume 50:Issue 2(2021)
• Page Start: 324
• Page End: 335
• Publication Date: 2021-03-02
• Subjects: Agricultural ecology -- Periodicals; Environmental engineering -- Periodicals; Pollution -- Periodicals; 630
• DOI: 10.1002/jeq2.20193
• Languages: English
• ISSNs: 0047-2425

Abstract

Abstract: Nitrogen (N) pollution from N inputs to agricultural soils contributes to widespread eutrophication and global climate change. One period susceptible to N losses is between winter grain harvest in summer and corn planting in spring in a corn ( Zea mays L.)–soybean [ Glycine max (L.) Merr.]–winter grain rotation. Cover crops used to immobilize N during this period often depend on tillage, which can exacerbate N losses. Therefore, we evaluated whether reduced‐till cover crops could decrease nitrate (NO3 – ) leaching and nitrous oxide (N2 O) emissions during this period. We tested this strategy in a cropping systems experiment on a 4‐ha plot in central Pennsylvania over 2 yr. This experiment compared a clover ( Trifolium pratense L.)–timothy ( Phleum pratense L.) cover crop no‐till underseeded into a standing spelt crop with a vetch ( Vicia villosa Roth)–triticale (× Triticosecale Wittm. ex A. Camus) cover crop established with tillage after spelt harvest. These systems were compared based on fortnightly N2 O emissions using static chambers ( n = 4 per six sample dates) and potential NO3 – leaching using anion resin bags ( n = 4 per system per year). Reduced‐till cover crops minimized peak N2 O emissions during the fall compared with tilled cover crops. However, reduced‐till cover crops did not decrease potentially leachable NO3 – relative to tilled cover crops despite decreases in soil inorganic N. Cover crop N isotopes revealed that clover N may have mineralized and leached over the winter. Our results suggest that reduced‐till cover crops can decrease N2 O emissions to mitigate the climate impact of agriculture but that winter‐hardy cover crops should be chosen to mitigate leaching. Core Ideas: Reduced‐till cover crop underseeding minimized peaks in soil nitrous oxide emissions. Nitrous oxide from reduced‐till systems was derived from nitrification pathways. Reduced‐till cover crops did not decrease leachable nitrate compared with tilled cover crops. Mineralization of clover cover crop biomass may lead to winter nitrate leaching.