Biomass Production And Nitrogen Accumulation By Hairy Vetch-Cereal Rye Mixtures: A Meta-Analysis

Agroecosystem services from cover crop mixtures are linked to aboveground biomass and total N content (kg ha(-1)). Reported values in the literature, however, vary for aboveground biomass and total N content of cover crop mixtures compared with monocultures. We conducted a meta-analysis using results from 55 site-years from 21 studies conducted in the United States to examine biomass and N content of hairy vetch (Vicia villosa Roth)-cereal rye (Secale cereale L.) mixtures compared with respective monocultures. Overall, hairy vetch-cereal rye mixtures produced 63 and 21% more biomass compared with hairy vetch and cereal rye monocultures, respectively. The N content of hairy vetch-cereal rye mixtures was 150% greater than that of cereal rye monocultures. When the proportion of hairy vetch seeds (by weight) exceeded 46% of the mixture, the mixtures accumulated equivalent or more N than the greatest yielding monocultures (usually hairy vetch). Compared with monocultures, a more consistent positive response of mixtures on biomass and N content was found on coarse-textured soils and following corn (Zea mays L.) rather than soybean [Glycine max (L.) Merr.] harvest. With increasing growing degree days (GDD), the biomass and N content of mixtures decreased relative to hairy vetch monocultures but increased relative to cereal rye monocultures, suggesting better performance of hairy vetch at higher GDD. We conclude that hairy vetch-cereal rye mixtures can produce equivalent or more biomass than both monocultures and accumulate as much N as hairy vetch, and that the relative productivity of mixtures depends on soil type, previous crop, seeding proportion, and GDD.