Cover crop mixtures enhance stability but not productivity in a semi‐arid climate
2021
Franco, Jose G. | Gramig, Greta Gaye | Beamer, Kenneth P. | Hendrickson, John R.
Cover crops are a critical component of sustainable agroecosystems, yet their performance in semi‐arid environments with short growing seasons and highly variable precipitation is inconsistent. To evaluate productivity and stability of single species vs. multi‐species cover crop plantings with variable water input, cover crops were evaluated at two sites in North Dakota under dryland and dryland plus irrigation conditions. Cover crop treatments consisted of three warm‐season monocultures, a three warm‐season species mixture (MIX3), and a three warm‐season and three cool‐season species mixture (MIX6). Averaged across year and water regime, biomass production was not greater for mixtures (8,693 kg ha–¹, MIX3; 10,212 kg ha–¹, MIX6) than for the most productive monoculture (11,295 kg ha–¹, sunflower [Helianthus annuus L.]) at the West site. The same held true at the East site (7,486 kg ha–¹, MIX3; 8,603 kg ha–¹, MIX6), with cowpea [Vigna unguiculata (L.) Walp.] producing the most biomass, 10,886 kg ha–¹, of all monocultures. At the West site, variability in production was lowest for MIX6 when pooled across year and water regime (CV = 25%) compared to monocultures (CV ≥ 49%). At the East site, cowpea had the lowest CV (24%) while mixtures averaged 35%. Pooled across sites, production in the MIX6 plots had the lowest variability (29%). Grasses consistently contributed to high proportions of total biomass production compared to other functional types. Multi‐species cover crop mixtures are more versatile than single species plantings across climates, and resilient cover crop mixtures integrated into semi‐arid crop rotations as full‐ season plantings should include warm and cool season grasses.
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