| Abstract/Contents: | "Emerging weeds are highly competitive during turfgrass establishment; therefore, soil fumigants are often used to reduce weed seed populations. Alternative methods to soil fumigants are being explored because applications such as methyl bromide are being phased out. Soil sterilization by solarization and soil-heating are possible alternatives for chemical fumigation. Traditionally soil sterilization techniques utilize transparent plastic mulch to cover the soil surface. This process confines radiant-heat below the plastic, consequently transferring heat to the soil. Our alternative methods utilize intense heat from propane burners to raise soil temperatures and potentially reducing seed viability of weed seed populations. Soil-solarization and flame-heating experiments were conducted at Auburn University Turfgrass Research Unit to evaluate soil sterilization effectiveness prior to turfgrass establishment. Treatments for 'Zenith' zoysiagrass (Zoysia japonica Steud.) and tall fescue (Lolium arundinaceum) research trials were initiated on June 1, 2009 and September 2, 2009, respectively. Marvyn loamy sand soil was tilled and prepared for turfgrass seeded establishment. Treatments included soil-solarization, dazomet (389 kg ha-1), flame-heating, and emerged-weed flaming (covered with germination cloth or uncovered). Germination cloth was applied or not-applied to soil surface of emerged-weed flaming plots. Germination cloth was used to stimulate weed emergence. Soil-solarization utilized 6 mm, clear, polyethylene plastic applied by hand. Flame-heating and emerged-weed flaming utilized a PL-8750 flame sanitizer (Flame Engineering Inc., LaCrosse, Kansas, USA) commonly employed for soil sanitation of poultry production houses. Flame-heating is direct soil flaming to increase soil temperature to kill weed seed. Emerged-weed flaming is employed in the same fashion as flame-heating but allows weeds to emerge before treatment; thereby potentially depleting the weed seed bank by killed emerge weeds and seed heating. Dazomet was applied at 29 days before turfgrass establishment. Soil-solarization treatment was applied 29 days prior to establishing tall fescue and 42 days prior to 'Zenith' zoysiagrass establishment. Flame-heating and emerged-weed flaming treatments were conducted 1 day prior to establishing tall fescue and 'Zenith' zoysiagrass. Visual percent weed cover, percent turfgrass cover, and plant counts were conducted 1, 22, and 43 days after seeding (DAS). Uniform weed species included carpetweed (Mollugo verticillatta), old world diamond flower (Oldenlandia corymbosa), and spotted spurge (Chamaesyce maculate). All weed species present in research plots were combined for data analysis as total weed coverage. All treatments reduced weed cover relative to the non-treated in the tall fescue research trial. Weed cover was less than 10 % for all treatments other than dazomet and non-treated at all rating dates. Soil-solarization resulted in 3, 7, and 9 % weed cover at 1, 22, and 43 DAS, respectively. Dazomet resulted in 4, 20, and 16 % weed cover at 1, 22, and 43 DAS. Flame-heating resulted in 0, 0, and 1 % weed cover at 1, 22, and 43 DAS, respectively. Emerged-weed flaming (uncovered) at 1, 22, and 43 DAS resulted in 0, 2, and 4 % weed cover, respectively. Emerged-weed flaming (covered) produced 0 % weed cover for all rating dates following application. Non-treated resulted in a 61, 89, and 53 % weed cover at 1, 22, and 43 DAS, respectively. Reductions in weed cover from 22 to 43 DAS by non-treated and dazomet treatments may be attributed to the increasing competition from establishing turfgrass. Weed cover for all treatments in 'Zenith' zoysiagrass research trial was greater than tall fescue. All treatments reduced weed cover relative to the non-treated. Soil-solarization resulted in 2, 11, and 47 % weed cover at 1, 22, and 43 DAS, respectively. Dazomet resulted in 1, 14, and 65 % weed cover for 1, 22, and 43 DAS, respectively. Flame-heating resulted in 6, 28, and 86 % weed cover at 1, 22, and 43 DAS, respectively. Emerged-weed flaming (uncovered) at 1, 22, and 43 DAS resulted in 0, 11, and 57 % weed cover, respectively. Emerged-weed flaming (covered) obtained the least amount weed cover at 0, 2, and 23 % at 1, 22, and 43 DAS, respectively. Non-treated resulted in 11, 58, and 98 % weed cover at 1, 22, and 43 DAS, respectively. These results indicate soil sterilization by flaming and solarization is an acceptable means of reducing weed seed populations before seeded turfgrass establishment. Obvious differences exist in the results between the two studies that could be accredited to the timing of the applications, temperature achieved by treatments, life cycles of weed species present, establishment rates, and growth habit of turfgrass. Both studies demonstrate a high potential for reducing weed populations through emerged-weed flaming covered with germination cloth." |
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