Planting date and staggered seeding affect biomass production and winter survival in a cereal-legume cover crop mixture

Background/Question/Methods

Cereal-legume cover crop mixtures seek to combine the distinct but complementary characteristics of grass and legume species to maximize the provision of nitrogen fertility and other services within cropping systems. Cereal rye (Secale cereale L.) and the legume hairy vetch (Vicia villosaRoth) are common constituents of such mixtures, but performance depends heavily on planting dates and the competitive dynamics between the two species. Because interference from rye has the potential to limit the growth of vetch in mixtures, staggered (delayed) seeding of rye following vetch could improve vetch performance and nitrogen accumulation in the cover crop stands. A two-year study was conducted to investigate how vetch planting date and the length of a rye seeding stagger affect biomass production and vetch winter survival in rye-vetch mixtures. The treatment design was a two-way factorial with three vetch planting dates (late August, mid September, and late September) and three lengths of rye stagger (0, 120, and 230 growing degree days (GDD) base 4°C after vetch planting). 

Results/Conclusions

Later planting of co-seeded (0 GDD stagger) mixtures resulted in cover crop stands with less total biomass and a lower proportion of vetch biomass in the spring. At earlier planting dates, staggering rye seeding increased vetch biomass production compared with co-seeded mixtures without decreasing total mixture biomass, while staggering seeding at later planting dates generally did not affect vetch biomass production and decreased total mixture biomass. Furthermore, at later planting dates, staggering rye seeding by 230 GDD resulted in reduced vetch winter survival compared with co-seeded mixtures.  Although benefits to vetch biomass production were observed with staggered seeding when mixtures were planted earlier in the season, results from this proof-of-concept study may not reflect actual on-farm outcomes. Additional research is needed to determine whether on-farm benefits of staggered seeding would justify the additional costs and management complexity. However, the increasing dominance of rye over vetch biomass in co-seeded mixtures planted later in the fall is an important consideration for growers, particularly when nitrogen fertility derived from the cover crop is a primary concern.