Pea-based cover crop mixtures have greater plant belowground biomass, but lower plant aboveground biomass than a pure stand of pea

In eastern Canada, organic grain producers have a rising interest in using cover crop mixtures instead of pure stands to maximize ecosystem services. Yield stability and belowground biomass of cover crop mixtures have however received limited attention in the scientific literature, although they do affect ecosystem services. The aims of this study were to evaluate the aboveground and belowgmund biomass and yield stability of pea-based cover crop mixtures, and to assess species-specific contributions to aboveground biomass. In a field experiment conducted at three site-years in Quebec, Canada, a pure stand of field pea (Pisum sativum L.) and cover crop mixtures of 2, 6, and 12 species, all including field pea, were compared to a weedy control (without cover crop). The mixtures were seeded according to a substitutive unbalanced design. The proportion of field pea ranged from 45% to 93% of the aboveground plant biomass within all mixtures. Among all site-years, pure stand of field pea provided the highest aboveground biomass (2636 kg ha(-1)), followed by the 2-species mixture (2320 kg ha(-1)) and both multi-species cover crop mixtures (mean of 1849 kg ha(-1)). Aboveground biomass was inversely correlated to cover crop diversity (Pearson coefficient of -0.73), and inversely correlated to weed biomass (Pearson coefficient of -0.54). Pure stand of field pea had the lowest belowground biomass and stability (693 kg ha(-1), CV of 28%) when compared to mixtures (886 kg ha(-1), CV of 14% on average). This study confirms that the value of pea-based mixtures, compared to a pure stand of field pea, lies mainly below the soil surface rather than above it. This could likely enhance many soil-related ecosystem services.

Automated summary

In this study, the aboveground and belowground biomass as well as yield stability of pea-based cover crop mixtures were evaluated. Pure stand of field pea had the highest aboveground biomass but lowest belowground biomass and stability, while mixtures showed higher stability and potential soil-related ecosystem services. The study highlights the importance of cover crop mixtures over pure stands in maximizing ecosystem services.