Vinasse and Biochar Effect On Germination of Three Weed Species.

Vinasse and biochar are byproducts of biofuel production that can be used as soil amendments to return nutrients to the field and improve soil quality. Although there is abundant information about the benefits of biochar and vinasse on soil properties, little is known about their effect on weed communities. We hypothesized that weed seed germination could be affected by biochar and vinasse addition to the soil, and that different weed species would show different responses to these soil amendments. The objective of this study was to determine the effect of vinasse and biochar on the germination of palmer amaranth (Amaranthus palmeri), sicklepod (Senna obtusifolia) and southern crabgrass (Digitaria ciliaris). Laboratory germination experiments were conducted mixing four rates equivalent to vinasse 0, 10, 20, and 40 L m^-2 (untreated check, 1X, 2X, and 4X), and biochar 0, 0.5, 2.5, and 12.5 kg m^-2 (untreated check, 1X, 5X, and 25X) with a sandy loam soil. The 1X rate was based on dry matter production of 16.5 Mg ha^-1, typical for sweet sorghum grown in the region. The addition of biochar to the soil did not affect the germination of any of the studied species. The addition of liquid vinasse had a negative effect on germination across all species. However, sicklepod germination was less affected by vinasse than the other two species. Vinasse at 1X and 2X rates reduced germination of palmer amaranth and crabgrass by 50% and 30%, respectively, compared to the untreated control, while sicklepod seeds showed no reduction. When vinasse was added at 4X rate, sicklepod, palmer amaranth and crabgrass germination was reduced on 72, 72 and 59%, respectively. The results of this study suggest that the use of vinasse as a soil amendment under field conditions could favor changes in weed community structure by differentially modifying germination rates.