Managing bermudagrass competition to overseeded alfalfa

Abstract

Abstract Overseeding alfalfa (Medicago sativa L.) into existing bermudagrass [Cynodon dactylon L. (Pers.)] swards may reduce N fertilizer inputs and improve seasonal distribution of forage. However, achieving successful alfalfa stands in mixture with bermudagrass is difficult because of competition from the grass. This experiment's objective was to assess strategies for managing bermudagrass competition to alfalfa during establishment and subsequent stand life. During 2020 and 2021, a 2 × 2 × 2 factorial was replicated five times in a randomized complete block design. The treatment factors included the glyphosate rate [N‐(phosphonomethyl) glycine], the initial bermudagrass stubble height (SH), and N fertilizer rates. Before planting alfalfa in November 2019, bermudagrass swards were treated with glyphosate at 0 or 890 ml ha–1 and clipped to a SH of 5 or 15 cm. During harvest seasons, N fertilizer was applied at 0 or 40 kg N ha–1 harvest–1. Glyphosate and SH had minimal effect on alfalfa establishment, forage accumulation (FA), and persistence. Application of N in 2020 increased mixture (34%) and bermudagrass (30%) FA over zero N, but alfalfa FA and proportion in mixture FA were not affected by N. In 2021, mixture FA was not affected by N, but alfalfa FA (5,030 vs. 2,380 kg ha–1) and proportion (63 vs. 25%) were greater for 0 than for the 40 kg N ha–1 rate. We conclude that N application increases first‐year alfalfa–bermudagrass mixture FA by increasing bermudagrass production, but it reduces second‐year alfalfa contribution, resulting in lesser alfalfa FA and mixture nutritive value and a shorter harvest season.