TY - JOUR T1 - Effects of Various Vineyard Floor Management Techniques on Weed Community Shifts and Grapevine Water Relations JF - American Journal of Enology and Viticulture JO - Am. J. Enol. Vitic. DO - 10.5344/ajev.2015.15050 SP - ajev.2015.15050 AU - Kerri L. Steenwerth AU - Arturo Orellana-Calderón AU - Robert C. Hanifin AU - Chris Storm AU - Andrew J. McElrone Y1 - 2016/01/05 UR - http://www.ajevonline.org/content/early/2015/12/23/ajev.2015.15050.abstract N2 - Adoption of permanent cover crops and no-till systems is considered integral to achieving California state air quality standards regulating airborne particulate matter, as indicated in Senate Bill 656. Imposition of such management techniques in a vineyard could create competition with vines for limited water resources. We evaluated the effects of permanent, untilled and mowed cover crops that were either tilled or mowed on vineyard floor composition, weed populations, vine water relations and growth, and fruit composition over three years within a mature commercial Merlot vineyard subjected to deficit irrigation in Lodi, San Joaquin Valley, California. The vineyard floor in this experiment supported resident vegetation that was tilled (standard grower practice), an oat cover crop, or a legume/oat cover crop. The two planted cover crops were either tilled or mowed (i.e. no-till). Biomass of cover crops, weeds and legumes varied by year and treatment, but consistent effects among treatments were not observed. Weed species composition and cover segregated with the presence or absence of tillage rather than cover crop type, and weed species composition of the resident vegetation was distinct from those in the cover crop treatments. Some treatments like ‘Oats/Legumes + NoTill’, ‘Oats + NoTill and ‘Oats/Legumes + TillResident Vegetation + Till’ reduced soil water content (Θv) in at least one of shallow three soil layers spanning 0–30cm, 30–60cm and 60–100cm in 2008 and ‘Oats/Legumes + NoTill’ in the two upper layers in 2009, but these differences had no consistent influence on plant water status. Distinctions in Θv between years were attributed partly to the cessation of rainfall two months earlier in 2008 than 2009, despite similar total annual quantities. Significant reductions in Θv imposed by the ‘Oats/Legumes+NoTill’these treatments did not reduce vine vegetative growth in one year, but these effects did not manifest in yield and fruit composition. Values for the Ravaz Index for two of the three years indicate that the vineyard was overcropped for all treatments, but maximizing production in this region is a common practice. Weak competitive effects of the cover crops for water were likely associated with the use of a well-established mature vineyard, and demonstrated that these management strategies could be employed to improve air quality to meet California air quality regulations with limited few effects on the vine water status and productions. ER -