Lowry, C. J. and D. C. Brainard. 2016. Strip-intercropping of rye–vetch mixtures affects biomass, carbon/nitrogen ratio, and spatial distribution of cover crop residue. Agronomy Journal 108:2433-2443.

Altering the spatial arrangement of cover crop mixtures with strip-intercropping is an under-explored strategy that may enhance cover crop performance and provisioning of ecosystem services. We hypothesized that strip-intercropping of a cereal rye (Secale cereale L.; “rye”) and hairy vetch (Vicia villosa Roth; “vetch”) mixture would increase cover crop productivity and concentrate low C/N vetch residue within the future crop zone, thereby increasing the potential for improved N use efficiency. We conducted a field study in southwestern Michigan to examine how strip-intercropping of rye–vetch mixtures influences: (i) total cover crop productivity, and (ii) the spatial distribution and C/N ratio of rye–vetch residues. Spatial arrangements included the standard full-width mixture (MIX) in which rye and vetch were sown together in the same rows; and segregated mixtures with either two rows of rye alternated with two rows of vetch (SEG2) or three rows of rye alternated with one row of vetch (SEG1). Benefits of strip-intercropping for reducing interspecific competition appear to have been offset by the costs of increased intraspecific competition and/or reduced facilitation. Over 5 site-years, strip-intercropping either had no effect or reduced total rye–vetch biomass or the biomass of component species relative to MIX. However, SEG2 resulted in greater concentration of N-rich vetch tissue and a lower C/N ratio of both aboveground and belowground rye–vetch biomass in the crop-planting zone. Strip-intercropping may be a promising strategy to increase future crop access to mineralized N, and improve N use efficiency in agroecosystems.

DOI: 10.2134/agronj2016.04.0189

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KBS Landscape

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