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‘Pinot noir’ grapevines were grown in a pot-in-pot system using a red-hill-soil where volumetric soil water content (uv) was carefully controlled. Four-year-old vines were supplied with one of two irrigation regimes (wet or dry) between véraison and fruit maturity and the experiment was repeated over 2 years. From véraison to harvest, vines in the wet treatment received irrigation whenever uv approached ’15% maintaining leaf water potential (Cleaf) above –1.0 MPa. Vines in the dry treatment received irrigation when uv approached 11% to 12% and experienced significant water stress (Cleaf ’–1.4 MPa) before water was re-supplied. Vines were destructively harvested at véraison and at fruit maturity to determine biomass and nutrient content in the current season’s above-ground tissues. Fruit yield, maturity indices, and must nutrient composition were measured at maturity. Irrigation did not influence vine growth in either year nor did it influence yield or fruit maturity indices. Irrigation also had no influence on leaf, whole cluster, or must mineral nutrient concentrations. Vine growth, yield, and nutrient status in leaves and musts varied by year. Vegetative growth was greater in 2007 than 2008, whereas yield and cluster weights were greater in 2008. Also in 2008, whole clusters obtained a greater proportion of dry matter and nutrients after véraison when differing irrigation treatments were imposed. Nonetheless, irrigation did not affect must chemical composition. These findings suggest that periodic post-véraison water deficits that are moderate to severe have little effect on berry nutrient and sugar accumulation in ‘Pinot noir’ cropped at typical levels for this variety. Previous findings of mineral nutrient accumulation in whole ‘Pinot noir’ clusters from a non-irrigated vineyard suggested that post-véraison nutrient [particularly nitrogen (N), phosphorus (P), and potassium (K)] import to berries could be limited by low soil water content (Schreiner et al., 2006). However, juice nutrients, including yeast assimilable nitrogen (YAN) concentration, were not determined in that study. Increasing water supply to grapevines, whether accomplished with varying irrigation levels or as a result of seasonal differences in rainfall, can increase must YAN levels (Nicolini et al., 2004; Wade et al., 2004). Seasonal variation in must YAN concentrations was weakly correlated with the amount of late summer rainfall over a 5-year period in a western Oregon ‘Pinot noir’ vineyard (P.A. Skinkis, unpublished data). Greater water supply to vines is also known to increase vine K status and must K concentrations thereby affecting wine pH (Mpelasoka et al., 2003, and references therein). However, when water supply was altered after bunch closure or véraison, effects on must K have been inconsistent (Etchebarne et al., 2009; Matthews and Anderson, 1988; Naor et al., 1993). The impact of late-season vine water supply on must P levels in grapevines is not known (Schreiner et al., 2013). An irrigation treatment was imposed on ‘Pinot noir’ grapevines to understand if a water deficit applied between véraison and harvest would reduce must nutrient levels. A post-véraison deficit was chosen to coincide with the time when soil water content is typically at its lowest seasonal point for non-irrigated vineyards in western Oregon (Schreiner, 2005; Schreiner et al., 2006). In addition, it was hypothesized that greater water stress during ripening would alter sugar accumulation in berries, as often found in other studies (Matthews and Anderson, 1988; Naor et al., 1993). A pot-in-pot system was used to reliably incur a water deficit during late summer because the relatively small surface area of the pots (20% of the vineyard floor surface area) intercepts little rainfall (Schreiner et al., 2013). This article reports the impact of a post-véraison water deficit on vine growth, yield, and nutrient status in leaves and musts. Materials and Methods Grafted ‘Pinot noir’ grapevines (Dijon 115 clone on 3309C rootstock) were grown in 60-L pot-in-pot microplots, as previously described (Schreiner et al., 2013), for 3 years before data collection. Sixty microplots were planted in 2004 and another 60 were planted in 2005 in two adjacent rows comprised of five blocks of 10 vines each. Half of the vines were randomly placed in either the wet or dry treatment, where different levels of water were supplied between véraison and harvest in the experimental year and in the previous year (see below). Data were collected from 4-year-old vines producing their first full crop; thus, vines measured in 2007 were planted in 2004, and vines measured in 2008 were planted in 2005. Vines were spaced at 1.0 m · 3.2 m, cane-pruned, and head-trained on a single Guyot system using vertical shoot positioning. The head height of vines was 0.6 m above ground and main shoots were trimmed 2 weeks after fruit set at a height of 2.6 m above ground. Pots were filled with a 1:1 (vol:vol) mixture of coarse sand (Pre-Stress Sand Mix; Knife River Inc., Corvallis, OR) and Jory series soil (fine, mixed, active, mesic Xeric Haplohumult) collected from the Oregon State University, Woodhall Research Vineyard (Alpine, OR). Dolomite lime (50% CaCO3, 40% MgCO3) was added to the mixed soil at a rate of 25 g·kg dry soil to raise soil pH to 6.0. Each microplot was fertilized at budbreak in each year with 50 g of 20N–4.4P–16.6K complete fertilizer with micronutrients (Peters Professional water soluble fertilizer; Everris, Marysville, OH). Fertilizer was broadcast over the pot surface and incorporated into the upper 2 to 3 cm of soil. This provided the N equivalent of 34 kg·ha. Vines were drip-irrigated using four pressure-compensating emitters (1.9 L·h) per microplot attached to a ring of tubing to disperse water evenly throughout the pots. Irrigation inputs were managed based on qv and vine water status. The qv was measured by time domain reflectometry (TDR) using 20 cm buriable, waveguides (6005TU-L20; Soil Moisture Equipment Corp., Santa Barbara, CA) that were installed vertically in two microplots per block at a depth of 10 cm below the soil surface halfway between the middle and side of the pots. The qv was monitored daily from véraison to harvest, and irrigation was applied whenever qv approached the target soil water content desired. TDR measurements were taken at 1600 HR Pacific Standard Time. The qv at field capacity and the permanent wilt point were previously determined in this soil mix at a bulk density of 1.35 g·cm with a psychrometer (SC-10; Decagon Devices, Pullman, WA). The qv at field capacity was 24%, and qv at the permanent wilt point (soil Y = –1.5 MPa) was 9%. In situ wilt tests were also conducted in 2006 in Received for publication 20 May 2014. Accepted for publication 19 Aug. 2014. This project was funded by USDA-ARS CRIS projects #5358-21000-048-00D and #5358-21000-047-00D. We thank Matthew Scott, Timothy Nam, John Carter, Scott Robbins, Suean Ott, and Christopher Rennaker for technical assistance. To whom reprint requests should be addressed; e-mail Paul.Schreiner@ars.usda.gov. HORTSCIENCE VOL. 49(10) OCTOBER 2014 1335 | SOIL MANAGEMENT, FERTILIZATION, AND IRRIGATION

Effects of Post-véraison Water Deficit on ‘Pinot noir’ Yield and Nutrient Status in Leaves, Clusters, and Musts