Increasing Nitrogen Availability at Veraison through Foliar Applications: Implications for Leaf Assimilation and Fruit Ripening under Source Limitation in ‘Chardonnay’ (Vitis vinifera L.) Grapevines

Abstract

<jats:p>Viticulture in Michigan is often limited by cool and humid climate conditions that impact vine growth and the achievement of adequate fruit quality at harvest. Sugars, pH, acids, and yeast available nitrogen (YAN) are indices of quality and, as such, of suitability for wine production. The aim of this study was to evaluate the efficacy of foliar nitrogen (N) fertilization applied as a 1% w/v urea solution at veraison as a method to increase canopy N availability during the fruit ripening stage. To test the effect on different source sink conditions, we imposed three levels of defoliation (0%, 33%, and 66% of leaves removed per vine) and measured net photosynthetic rate (P<jats:sub>n</jats:sub>), leaf efficiency parameters, yield components, and fruit quality parameters. Apical leaf P<jats:sub>n</jats:sub> was increased by the 33% defoliation (+12% from the undefoliated control) and by the urea application (+6%) 2 weeks after veraison. In basal leaves we observed a reduction in chlorophyll content (SPAD) and maximum photochemical efficiency of PSII (F<jats:sub>v</jats:sub>/F<jats:sub>m</jats:sub>) as a result of the defoliation treatment and secondarily by the N application, which resulted in a reduction in P<jats:sub>n</jats:sub>. Therefore, mean shoot P<jats:sub>n</jats:sub> was unaffected by the treatments. Although neither main nor lateral shoot growth was increased by any defoliation treatment, both percent soluble solids (%SS) and berry weight were significantly reduced by the 66% defoliation treatment. Application of urea increased yeast available amino acids by 20% but did not impact %SS or other chemical parameters indicating a different accumulation pathway for sugars and amino acids in the berry.</jats:p>

Response of ‘Italian Riesling’ Leaf Nitrogen Status and Fruit Composition (Vitis vinifera L.) to Foliar Nitrogen Fertilization

“…No significant differences were observed considering yield parameters. It is in accordance to previous studies (Hannam et al, 2014;Lacroux et al, 2008;Tozzini et al, 2013), where foliar N application had no effect on yield parameters, which is expected since application was performed at veraison when grape composition, rather than yield, is affected.…”

“…As suggested by Neilsen et al (2010) and Tozzini et al (2013), earlier N application could affect both leaf and berry N accumulation. Research on late spring-applied (Conradie, 1990) and early summer-applied (Conradie, 1991) nitrogen showed that N translocation was mainly directed to bunches.…”

“…Previous findings showed that nitrogen fertilization applied either to the soil (Linsenmeier et al, 2008;Spayd et al, 1994) or foliarly (Hannam et al, 2014;Jreij et al, 2009;Tozzini et al, 2013) increases must total N content as well as individual N compounds.…”

Nutritional status differentially affect yield and must composition of hybrids andV. viniferavarieties established under cold climate conditions

“…In "New York Muscat", bunch weight was positively correlated with N levels at véraison and negatively correlated with Ca to K. N in adequate levels are necessary for inflorescence primordium formation and for differentiation of flowers (Vasconcelos et al, 2008). Contrary to our results, bunch weight was not affected by foliar applications to grapevines at véraison (Tozzini et al, 2013). Low N status may be associated with berry growth (Hilbert et al, 2003;Rogiers et al, 2004).…”

Impact of Cluster Thinning and Basal Leaf Removal on Fruit Quality of Cabernet Franc (Vitis vinifera L.) Grapevines Grown in Cool Climate Conditions

“…For wine grape, an RI exceeding 12 indicates overcropping and less than 5 undercropping vine status, corresponding to leaf area to fruit weight of less of 8 cm 2 • g -1 or more than 14 cm 2 • g -1 , respectively (Kliewer and Dokoozlian, 2005), particularly for vines grown on a vertical shoot positioning trellis (VSP), most common used training system in cool climate viticulture. In a cool climate, with its low heat accumulation [growing degree-days (GDD)] and short growing seasons, a higher amount of leaf area and, therefore, a lower cropload is suggested to ripen the fruit to a desired level (Howell, 2001;Tozzini et al, 2013). Canopy management techniques such as basal leaf removal are frequently used to increase sunlight exposure and exposed berry temperature (Bledsoe et al, 1988;Smart and Robinson, 2008).…”