Interseeding cover crops in sugar beet

Abstract

Sugar beet (Beta vulgaris L.) production leaves very little residue to protect the soil from erosion during late fall and early spring. Biomass from interseeded cover crops provides an opportunity to protect soils from erosion during the fallow period. A three-year field study was conducted to assess cover crop interseeding in sugar beet production systems under rainfed conditions in Ada, MN, USA. Specifically, the impact of cover crop interseeding time, early (mid-June) vs. late (late June or early July), and four species, winter pea (Pisum sativum L.), rye (Secale cereale L.), winter camelina [Camelina sativa (L.) Crantz], and brown mustard (Brassica juncea L.), on cover crop biomass and sugar beet root yield, sucrose concentration, and recoverable sucrose yield. Cover crop biomass accumulation in sugar beet varied across years depending on distribution of rainfall after interseeding. Considering all three years, above ground biomass of cover crops ranged between 28 kg ha−1 to 2347 kg ha−1 at sugar beet harvest. Early interseeded cover crops produced threefold greater cover crop biomass than late interseeded cover crops. Across years, mean aboveground biomass produced by species was from highest to lowest, winter pea > rye > brown mustard > winter camelina. The highest recoverable sucrose yield was observed with early-interseeded brown mustard (13.8 Mg ha-1), late-interseeded winter camelina (11.2 Mg ha-1), and late-interseeded rye (10.46 Mg ha-1) in 2018, 2019, and 2020 growing seasons, respectively. Three years of results have shown that sugar beet grown with interseeded cover crops will produce root yields comparable to the control with no cover crops. Cover crops had no negative impact on root yield and sucrose concentration, but the selection of species and planting time affected growth and cover provided by the cover crops. This study provides evidence that interseeded cover crops offer a good option for protecting the soil during fallow periods in sugar beet production systems, without negatively affecting sugar beet yield or quality.