Altering Weed Populations Prior to Turfgrass Establishment by Soil Solarization, Flaming, and Dazomet.

Germinating annual weeds are highly competitive during turfgrass establishment. Soil fumigants are often used to reduce weed seed populations, however alternative methods are needed.  Soil-sterilization and flame heating experiments were conducted at Auburn University to evaluate effectiveness prior to turfgrass establishment. Treatments initiated in 2009 and 2010 included soil-solarization, dazomet (389 kg ha^-1), flame-heating, and emerged-weed flaming (covered with germination cloth or uncovered). Flame heating is direct soil flaming to increase soil temperatures to kill weed seed.  Emerged-weed flaming is employed similarly to flame-heating but allows weeds to emerge before treatment. Seeded turfgrass species included ‘Zenith’ zoysiagrass (Zoysia japonica Steud.), seashore paspalum (Paspalum vaginatum Sw.), and ‘TifBlair’ centipedegrass (Eremochloa ophiuroides (Munro) Hack.). Plant counts for old world diamond flower (Oldenlandia corymbosa), spotted spurge (Chamaesyce maculata), Virginia buttonweed (Diodia virginiana L.), and carpetweed (Mollugo verticillatta) were conducted 3 weeks after seeding turfgrass.  Solarization decreased old world diamond flower, Virginia buttonweed, spotted spurge, and carpetweed 54, 94, 81, and 92%, respectively. Dazomet decreased old world diamond flower, Virginia buttonweed and carpetweed 78, 94 and 16%, respectively but increased spotted spurge 32%.  Flame-heating decreased all weed species except carpetweed increasing the number of plants per m² by 43%. Emerged-weed flaming conducted 1 day prior to seeding, emerged-weed flaming conducted 1 and 21 days prior to seeding, emerged-weed flaming covered conducted 1 day prior to seeding and emerged-weed flaming covered conducted 1 and 21 days prior to seeding decreased Virginia buttonweed 4, 55, 58 and 57%, respectively; old world diamond flower 85, 74, 77 and 93%, respectively; carpetweed 81, 76, 75 and 91%, respectively and spotted spurge 25, 59, 83 and 94%, respectively. Studies demonstrated a high potential for reducing weed populations utilizing emerged-weed flaming after covering with germination cloth. These results indicate soil sterilization by flaming can reduce weed populations before seeded turfgrass establishment.