Description

Abstract: Alfalfa (Medicago sativa L.) has traditionally been established in the autumn in the southeastern USA, even though insects, disease, and/or moisture supply may limit successful conventional or notillage establishment. In previous studies, late-winter (February or March) no-till seedings failed because chemicals applied at time of seeding failed to suppress the grass. The objectives of this study was to evaluate autumn chemical suppression and/or killing of tall fescue (Festuca arundinacea Schreb. ‘Kentucky 31’), late-winter seeding date (February or March), and weed control in the seeding year on no-till establishment of ‘Cimarron’ alfalfa into a tall fescue dominant sward. Three, 2-yr field experiments were conducted during 1985 to 1987 on Typic Hapludult soils. Common to all experiments was a 23 factorial arrangement of treatments consisting of; (i) two late-winter seeding dates of alfalfa, mid-February or mid-March, (ii) autumn applied paraquat (l-l?-dimethyl-4,4?-bipyridinium ion) at 0.28 kg ha?1 a.i. or glyphosate [N-(phosphonomethyl) glycine] at 2.24 kg ha?1 a.i. for grass suppression, and (iii) the use of no weed control in the seeding year vs. weed control during the seeding year. A no-grass suppression treatment was included for each seeding date. Insect grazing damaged 15% of the alfalfa seedlings, with an average damage per plant of 4%. Autumn grass suppression followed by late-winter (February or March) no-till seeding of alfalfa resulted in alfalfa yields of 6.77 Mg ha?1 as compared to no-grass suppression yields of 3.27 Mg ha?1 for the seeding year. Weed control in the seeding year increased alfalfa yields in the March seeding 2.51 Mg ha?1 as compared to no-weed control in the seeding year. We conclude that late-winter (February or March) no-till seeding alfalfa into a cool-season perennial grass sward in the southeast region of the USA is an excellent alternative to autumn providing the grass is killed in the autumn prior to seeding.