Submitted to: Group of International Experts of Vitivinicultural Systems for CoOperation(GiESCO)
Publication Type: Proceedings
Publication Acceptance Date: 5/5/2009
Publication Date: 7/14/2009
Citation: Steenwerth, K.L., Baumgartner, K., Belina, K.M., Veilleux, L. 2009. SHIFTS IN VINEYARD WEED SEED BANK COMPOSITION IN REPONSE TO ORGANIC AND CONVENTIONAL WEED CONTROL PRACTICES. Group of International Experts of Vitivinicultural Systems for CoOperation(GiESCO). Interpretive Summary: We studied three weed control practices to determine if shifts in weed seedbank composition occurred and if these shifts reflected aboveground weed community composition. These weed control practices were the organic practice of soil cultivation and the conventional practice of glyphosate application. After three years of weed treatments, the composition of spring cultivation and fall-spring glyphosate weed communities tended to differ from each other, but the remaining two treatments showed little differentiation. Emergent seedlings from the seedbank did not reflect the composition of the aboveground weed community. Weeds that were dominant in the seedbank were not those that are likely to interfere with grape harvest procedures.
Technical Abstract: The aim of this research was to compare the organic weed control practice, soil cultivation, to the conventional practice, applications of the herbicide, glyphosate, in terms of their effects on weed seed bank in a vineyard system. The experiment was conducted in a commercial winegrape vineyard in the Napa Valley of northern California from 2003 to 2005. The vineyard was established in 1996 with Merlot (clone 314) on 110R rootstock (V. berlandieri Planch. X V. rupestris Scheele). The 0.84-m-wide section of soil in the vineyard row, where treatments were carried out, was level with the soil in vineyard the middles; vines were not elevated on berms. The annual treatments were winter-spring glyphosate, spring cultivation, fall-spring cultivation, and fall cultivation-spring glyphosate, and were applied to the berm. Composition of the weed seed bank collected in 2002 prior to treatment establishment differed little among treatments. After three years of weed treatments, detrended correspondence analysis indicated that the composition of spring cultivation and fall-spring glyphosate tended to differ from each other, but the remaining two treatments showed little differentiation. As determined by linear discriminant analysis, the specific weed species were associated with seed banks of certain treatments, yet not were likely to interfere with harvest operations due to phenology or morphology. Although Vulpia myuros was ubiquitous among treatments, its distribution between depths in the cultivated treatments indicated that tillage provided some homogenization of the seed bank along the vertical soil profile. The high frequency of V. myuros among treatment also indicates that the cover crop in the region between the vines affected the seed bank composition in the rows. The emergent seedlings from the seed bank study were not congruent with those measured aboveground in the field, suggesting that both treatment and microclimatic effects in the field may have influenced germination, and thus, aboveground composition.