Effect of vegetation suppression on the establishment of sod-seeded alfalfa in the Aspen Parkland

Abstract

Four trials were conducted on a heavily grazed bluegrass-dominated pasture located in east-central Saskatchewan to compare the establishment of alfalfa (Medicago media Pers. Drylander) and forage grasses with no suppression vs. suppression of the resident vegetation using either glyphosate or rotovation. Successful forage establishment was based on seedling count, herbage yield and an economic assessment using net present value. The test area had been cleared of mature aspen poplar (Populus tremuloides Michx.) and balsam poplar (Populus balsamifera L.) trees, treated with 2,4-D to control suckering and was subsequently invaded by native forbs and grasses, mainly bluegrasses. Alfalfa successfully established with or without suppression while smooth bromegrass (Bromus inermis Leyss. ’Carlton’) established only when a suppression treatment was applied. Forage yields, averaged over 4 yr and four trials, following sod-seeding and glyphosate at 2.5 kg ha−1 were 1973 and 612 kg ha−1 for alfalfa and bluegrass plus smooth bromegrass, compared to 1287 and 748 kg ha−1 for alfalfa and bluegrass plus smooth bromegrass, respectively, when there was no suppression of the resident vegetation. The low-cost, no-suppression sod-seeding treatment was as profitable as the sod-seeding treatment using glyphosate.Key words: Sod-seed, zero till, alfalfa, smooth bromegrass, economics, glyphosate