EFFECTS OF VEGETATION SUPPRESSION AND DRILLING TECHNIQUES ON THE ESTABLISHMENT AND GROWTH OF SOD-SEEDED ALFALFA AND BIRD’S-FOOT TREFOIL IN GRASS DOMINANT SWARDS

Abstract

The sod seeding of alfalfa (Medicago sativa L.) and bird’s-foot trefoil (Lotus corniculatus L.) was studied in three locations previously cut for conserved feed or used for pasture. At each location an experiment with a split-split-plot design was established with sod-seeded alfalfa and bird’s-foot trefoil as main treatments, methods of drilling as subtreatments, and methods of vegetation control as sub-subtreatments. Drilling was done with a John Deere PowrTill 1500 renovator and Øyjord plot drill equipped with shoe openers. The methods of vegetation control included mowing and spraying with 1:1-′dimethyl-4.4′bipyridinium dichloride (paraquat) or N-(phosphonomethyl) glycine (glyphosate) at the time of drilling. Sod seeding alfalfa resulted in greater dry matter yields than bird’s-foot trefoil. Alfalfa and bird’s-foot trefoil constituted 27 and 17% of total yield in the year after sod seeding and 17 and 4% in the 2nd year after drilling, respectively. Alfalfa performed better in a sward previously cut for conserved feed while bird’s-foot trefoil performed better in a field used for pasture. Both PowrTill and plot drill resulted in satisfactory seedling establishment although the yields of sod-seeded legumes were greater with plot drill than with PowrTill in the year after drilling. Vegetation suppression with paraquat and glyphosate did not improve the growth of sod-seeded alfalfa or bird’s-foot trefoil over the unsprayed treatment. In a heavy sward consisting mainly of Poa pratensis L., sod-seeded alfalfa, and bird’s-foot trefoil failed to establish.