Herbicide and Planting Date Influence Establishment of Sod‐Seeded Alfalfa1

Abstract

AbstractYield and quality of perennial grass pastures can be improved through sod‐seeding of alfalfa (Medicago sativa L.). Herbicides have been widely used for grass suppression in sod‐seeding; however, the influence of the time of application on herbicide effectiveness requires study. Our objective was to determine the effects of planting dates and rates and types of herbicides on alfalfa establishment and yield when interseeded into perennial grass sod. A field study was conducted for 2 years on a Typic Halaquol, fine loamy, over sand, mixed, mesic soil. Alfalfa was sod‐seeded into a mixed smooth bromegrass (Bromus inermis Leyss.), Kentucky bluegrass (Poa pratensis L.), and quackgrass (Agropyron repens L.) sod on 21 April, 10 May, 19 May, and 2 June in 1978; and 19 April, 4 May, 21 May, and 2 June in 1979. On each planting date, paraquat (1,1′‐dimethyl‐4,4′‐bipyridinium ion) and glyphosate [N‐(phosphonomethyl) glycine] were each broadcast sprayed at 0.6, 0.8, and 1.1 kg ha−1. Dalapon [2,2‐dichloropropionic acid] was broadcast sprayed at 3.4, 5.6, and 9.0 kg ha−1. Greatest seeding year legume yields were obtained with the medium or high dalapon rates for the April seeding dates or with the medium or high glyphosate rates for the late May seeding date. The lowest average legume yields across all herbicides occurred for the June seeding date each year. Dalapon was the most effective herbicide across all rates for suppressing grass and increasing alfalfa yields for the April planting dates each year when grass regrowth was limited. For the early May planting date, dalapon treatments had the lowest grass yields. Alfalfa yields for dalapon and glyphosate treatments were not consistently different. For the late May planting date, glyphosate provided the greatest grass suppression and alfalfa yields. Herbicides and herbicide rates can be selected for grass suppression and legume establishment based on extent of grass vegetative development. Under low rainfall conditions, grass suppression may not insure successful legume establishment.