A study was conducted to investigate the interaction of N fertilization rates and different irrigation amounts on N fertilizer recovery efficiency (REN) of Cabernet Sauvignon in a commercial vineyard near Oakville, California. The fertilizer treatments consisted of a control (no fertilizer) and two 15N labeled ammonium nitrate fertilizer applications (6.5 and 13.0 g N/vine). The N fertilizer was applied two weeks before anthesis. The irrigation treatments were various fractions (0.25, 0.5, and 1.0) of estimated vineyard water use (ETc), with the applied water amount for the 1.0 irrigation treatment from 7 Apr to 9 Sept equivalent to 312 mm. Midday leaf water potential (Ψl) was measured throughout the season to monitor vine water status. The labeled N fertilizer was detected in the petioles and leaf blades two weeks after application. Irrigation and fertilization treatments significantly affected midday Ψl. There were significant differences in aboveground vine biomass among the treatments. In general, those supplied with more water and/or N fertilizer had greater biomass compared with nonfertilized vines under deficit irrigation. Vine uptake of the 15N labeled fertilizer increased with increasing fertilization rates and irrigation amounts. The REN was significantly different between the two 15N fertilizer treatments (29% for 6.5 g N/vine and 24% for 13.0 g N/vine). REN at harvest for the 0.25, 0.5, and 1.0 ETc irrigation treatments was ~24, 28, and 27%, respectively, although not significantly different. The data indicate that fertilizer amount had a significant effect on REN under the conditions of this study and that irrigation rates at full ETc tended to increase REN in this vineyard when compared with deficit irrigation.
- ©2014 by the American Society for Enology and Viticulture