Abstract
With limited research supporting local nutrient management decisions in North Carolina grape (Vitis vinifera) production, field studies (2015–17) were conducted to evaluate late season foliar nitrogen (N) application on leaf and petiole N concentration and yeast assimilable N (YAN) in the fruit. Foliar urea (1% v/v) was applied at different rates and application times beginning pre-and post-veraison. Compared to soil applied N, late season foliar N substantially enhanced petiole N and grape YAN. Smaller split N applications were generally more effective in increasing YAN than single larger N rates. These data demonstrate the value of assessing plant N content at full bloom with petiole N analysis or remote sensing to guide foliar N management decisions. Additional field studies (2008–11) were conducted to evaluate pre-bud soil applied phosphorus (P) and potassium (K) effects on petiole P and K nutrient status. Fertilizer P and K were initially broadcast applied (0–896 kg P2O5 ha−1; 0–672 kg K2O ha−1) prior to bud-break in 2008–09 and petiole P and K at full bloom soil test P and K were monitored for three to four years after application. Soil test and petiole P and K were significantly increased with increasing P and K rates, which subsequently declined to near unfertilized levels over the sampling time depending on site and P and K rate applied. These data demonstrate the value of annually monitoring petiole P and K levels to accurately assess plant P and K status to better inform nutrient management decisions.
Highlights
Wine grape production is a rapidly growing industry in North Carolina (NC), which ranks 10th in the United States (US) in wine grape production, 7th in wine production, and represents a $2 billion total economic impact [1,2]
At Site A, soil samples were collected from the soil applied N plots, results were not significantly different from soil test data obtained from the untreated plots, residual soil applied N was not detected in at either site
The vineyards included in the P and K nutrient response studies were selected for potential wine grape response to soil applied P and K (Table 6)
Summary
Wine grape production is a rapidly growing industry in North Carolina (NC), which ranks 10th in the United States (US) in wine grape production, 7th in wine production, and represents a $2 billion total economic impact [1,2]. One potential solution to avoid excessive vine vigor associated with N applications in V. vinifera grapes grown in NC and other southeastern states is to foliar apply N in late-season to increase YAN while causing minimal changes to vine growth and disease potential. Foliar N was more effective in increasing juice YAN compared with early season soil applied N [36] These results confirm significant improvements in the aromatic profile and intensity of wines made from Tempranillo grapes treated with foliar N. The objectives of these studies were to: (1) evaluate late season foliar N application on YAN in the fruit, and (2) quantify soil and plant nutrient response to soil applied P and K
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